Wooden Floors 1 Laying and Repairing Wood

WOODEN FLOORS 1 LAYING AND REPAIRING WOOD

Translation: Karsten Lundager, University College Vitus Bering Denmark

WOODEN FLOORS 1 WOOD

THE WOOD INDUSTRY ADVISORY COUNCIL (TRÆBRANCHENS OPLYSNINGSRÅD) CONTENTS

Floor types...... 4

Flooring materials ...... 7

Substrates ...... 11

Fasteners and adhesives...... 17

Wood and moisture ...... 22

Requirements related to moisture 26

Floor heating ...... 31

Wet rooms...... 36

Acoustics ...... 38

Joints ...... 40

Laying instructions ...... 43

Renovation ...... 70

Damages and repairs ...... 72

Appendix...... 75

Wooden floors and

BR requirements...... 82

Terminology ...... 83

Literature ...... 85

Subject index ...... 86

2 PREFACE

This handbook demonstrates thoroughly In spite of different construction tested methods for the laying of wooden principles wooden floors are generally floors and describes such technical made of a natural product with the conditions which must be fulfilled in order variations in the material which to construct wooden floors correctly. The characterizes wood. choice of wooden floors and maintenance The quality of the wooden floor therefore are described in ³WOOD 47, Wooden highly depends on proper grading of wood Floors 2´. and on wood quality as well as the Both handbooks build on practical subsequent workmanship and maintenance. experience and take into consideration such There may be variations in the surface conditions that are applicable to structure of the wood, in the colour, in the construction work and to wood as a building grain pattern and in the density. material. It is such variations which, within certain The exposure to moisture during limits, add the life and glow characteristic construction and the inappropriate to natural materials. moistening of the wooden floor during use As wood adjusts to the variations in air may cause undesired damages because not humidity during the seasons of the year all materials and not all workmanship are there will be natural variations in the widths compatible with wooden materials. Most of the boards and therefore in the widths of building materials expand and contract the gaps between the boards. Normally, the when temperature changes, whereas wood gaps are closed during the summer and open expands and contracst with changing during the winter. humidity. This handbook primarily addresses It is important to take into consideration consultants and craftsmen within the the particular relation between wood and building industry, but has been so planned humidity ± both when laying and when that it may be used by clients, real estate maintaining wooden floors. The floors must administrators, and do-it-yourself people and be able to contract and expand independently as a lecturing aid in building design. in relation to other building components. In order to achieve the widest possible Also wooden floor should be laid as late as professional approach the handbook has possible in the building process in order to been elaborated in conjunction with floor secure that the indoor climate is sufficiently material suppliers and trade associations dry. In relation to moisture and exposure to who have most willingly contributed with moisture it is important to treat wooden professional knowledge and practical floors exactly as one would treat fixed experience. furniture and other furniture

Advisory Council for the Wood Industry (Træsbranchens Oplysningsråd) June 2004 Bjarne Lund Johansen

3 Battens FLOOR TYPES (chocked up with packing Wooden floors are floors made of boards, pieces) strips, blocks or laminated materials with a wooden core. Wooden floors may be divided into two main groups defined by the construction principle: Suspended floors include: ‡ Floors on battens (chocked up) ‡ Floors on joists Non-suspended floor include: Floor on battens ‡ Floating floors ‡ Glued floors ‡ Nailed floors Structural joists

Suspended floors Suspended floors are floors resting upon a linear support of joists or battens. The load on the floor is transferred through the boards and accepted by the underlaying battens or joists, see figure 1. Floors on battens Battens are chocked up on an under- laying structural floor made of such materials as concrete, clinker concrete or wood in order Floor on joists to establish a level surface for the wooden floor Figure 1 Suspended floors on battens and on Floors on joists structural joists Structural joists are the basic part of a wooden joist system on top of basements, crawl Non-suspended floors spaces and storey partitions. Suspended Non-suspended wooden floors are wooden floors may be constructed from supported throughout the floor surface by a boards or long parquet blocks. The boards structural sub floor made of such materials may be traditional solid floorboards or as concrete or building board. they may be laminated parquet floorboards Long parquet blocks are parquet blocks Floating floors with a length of more than 700 mm. Floors Floating floors can move freely (in relation to on joists and battens offer ample opportunities the sub floor) when the wood expands and for the placing of sound and heat insulating contracts with moisture variations (figure 2). materials in the cavity under the floor. The It is common practice to introduce an cavity may also be used for the running of additional layer between the wooden floor heating and electrical installations. and the sub floor in order to secure the free movement of the floor. This layer may be made of materials contributing to thermal or sound insulation (cork, foam or the like).

4 FLOOR TYPES Additional layer Glue

Floating floor - on Floor fixed with glue top of additional on concrete slab layer (here cork) structural floor

Glue Moisture barrier Structural subfloor (building board) Additional layer ± building board

Floating floor on Floor fixed with glue additional layer on structural floor made of wood- made of wood-based based building building board board Figure 3 Non-suspended floors – glued/nailed Additional layer Structural subfloor Glued and nailed floors Glued and nailed wooden floors are always fixed firmly on top of a plane and stable structural floor and supported throughout the entire surface, see figure 3. The structural floor can be made of concrete, light weight concrete or a wooden based subfloor or even a Floating floor on floating floor - for example made of structural sub floor glue joined boards. made of wood- On structural wooden joists it will be based building board possible to use the sub floor as a ³work floor´ during the construction period. Figure 2 Non–suspended floors - floating The underlay floor could also be an existing floor where a renovation is desired ± laying Floating floors may be laid on top of a a new floor on top of the existing. load distributing board or directly on top of the intermediate layer.

FLOOR MATERIALS 5 Floor construction - terminology Floor cover The uppermost independent layer of the Additional layer floor, i.e. the floor covering constitutes the finished floor surface. The floor covering can Structural floor be made of planks, parquet blocks, PVC or linoleum. Applied finishes such as varnish or other surface treatments are not considered as independent floor coverings. Structural floors are placed under the floor cover but above the structural joists. The structural floor must constitute a continuous surface making it suitable for example as Structural joists D´work floor´ and as underlay for a thin floor cover. The structural floor can be Structural joists + made of building board (wood-based) laid on Figure 4 Floor construction - Structural floor = pressure resistant insulation, or laid on structural floor terminology construction battens, structural joists, or on a concrete screed. Notice that thin insulation layers like cork based cardboard etc. are additional layers and not regarded as structural floors. The function of the structural floor construction is primarily to accept and transfer loads. The structural floor construction could be wooden joists, concrete slabs etc. See figure 4 . Table 1: An overview of different flooring materials and their application in different floor constructions. The highlighted areas indicate that the product can be used for the said purpose. The text indicates limitations.

Floor types Floor materials Floor - Parquet Parquet Mosaic Wood Laminate End boards blocks boards parquet veneer floor grain floorboards boards wood blocks Suspended Minimum Long Minimum Minimum floors thicknes blocks 20 mm 20 mm Floors on s 20 mm minimum thicknes thickness battens or floor 20 mm s joists thicknes s Non-suspended Only on Only clip Only on Only on floors floating system floating floating Floating floors subfloor subfloor subfloor Nailed floors Minimum Minimum Minimum Minimum 12 mm 12 mm 12 mm 12 mm thick – thick – thick – thick – secret secret secret secret nailing nailing nailing nailing Glued floors Short Ask blocks supplier*) * Only in widths as specified by the supplier.

6 FLOOR TYPES Floor materials -Tongue Stress groove Groove

Floorboards Bottom rebate Guiding groove Floorboards are solid boards primarily produced from softwoods such as pine, spruce, douglas or pitch pine. Hardwoods are used to a lesser extend for example oak or merbau. Floorboards are planed, tongued and grooved boards, normally produced in widths ranging from 75 to 180 mm and in thicknesses from 14 to 30 mm. It is possible to place special orders for thicknesses up to 40 mm and widths up to 450. The length is normally between 1.8 and 5.4 m. In case boards are ordered as ³random length´ it is possible that some planks may be shorter. In case boards are ordered with a fixed length, it is likely that some planks (normally 5-10%) will be shorter as the producer needs to economize when cutting the tree trunk. Because floorboards look like planks, they are sometimes called floor planks although the products do not have sufficient thickness to merit that term (a planed thickness of minimum 42 mm). No standards have been defined for the dimensions and profiles of floorboards. That is why floorboards from different manufacturers will normally not fit together. Tongue and groove are often placed nearer the bottom side of the board in order to Figure 5 Floorboards provide the floorboards with the thickest possible wearing layer. The bottom rebate is drying and planning. Grooves on the bottom made 0.5 mm deeper than the top rebate in side are not always stress grooves but may order to secure a tight fit between the also be so-called guiding grooves used in boards, see figure 5. connection with the profiling process. Floorboards are often supplied with so- Boards with a minimum thickness of 20 called stress grooves at the bottom side in mm may be laid directly on floor battens or order to counter the natural (cupping) joists as a suspended floor. The distance curving in the boards. Stress grooves are between supports shall be determined in only considered effective when they have a accordance with thickness and load, see depth corresponding to two thirds of the tables 3 and 4. Boards less than 20 mm in initial thickness of the board, i.e. before thickness require the existence of a sub- floor in order to get sufficient support.

FLOOR MATERIALS 7 Strip floor / parquet blocks Parquet blocks are normally single staves in -Tongue Groove solid wood. The blocks are rectangular with tongue and groove (T&G). However Chamfered edge solid blocks are also available without T&G see figure 6. Parquet blocks are produced from traditional European wood species such as beech, oak and ash but also such exotic species as padouk, merbau, doussie and wenge are used. Parquet blocks are normally 200-700 mm long and 50-70 mm wide. Parquet blocks are also produced as so-called long blocks with a length of 700-1200 mm. Parquet blocks are either glued or nailed. Long blocks with a minimum thickness of 20 mm may be laid as a suspended floor.

Parquet boards Parquet boards are made from solid parquet blocks joined together in a prefabrication process. It is common practice to join two or three blocks in parallel, using a special dovetail joint. The boards are supplied with a T&G along all four sides ad are supplied Figure 6 Parquet blocks in length as normal floorboards see figure 7. Parquet boards can be laid using the same methods as those used for ordinary Dovetail joint- Tongue floorboards, i.e. as a suspended floor when the board thickness is minimum 20 or as a nailed floor on level structural floor. Parquet boards may also be applied as Groove Groove for clip floating floors joined with purpose made clips, see page 21.

Figure 7 Parquet boards

8 FLOOR MATERIALS Parquet tiles Parquet tiles are factory joined parquet blocks glued together to constitute larger units, see figure 8. Parquet tiles are laid as a glued floor.

Mosaic parquet Mosaic parquet is made of small parquet blocks joined together in order to form panels/tiles, see figure 8. The blocks may be glued to an open fabric or mesh or joined with steel wire. The fabric or mesh is normally glued to the back side of the panel, but may also be placed on the front side. In the latter case it will be removed when the floor is finally sanded after laying. Mosaic parquet is laid as a glued floor.

Wood veneer floorboards Wood veneer floorboards are normally made as a three layer laminate. The bottom layer is made of soft wood with fibres oriented along the board. The core is made of chipboard, plywood, MDF or cross bonded wooden strips. The topmost layer Figure 8 Parquet tiles and mosaic parquet consists of minimum 2 mm wood veneer. In most cases this layer is 3-4 mm thick. The wood veneer is separated into staves similar in appearance to solid parquet Wood veneer surface blocks, see figure 9. In this way it is possible to obtain wood veneer floorboards with appearance similar to floorboards and parquet blocks. See figure 9. Bottom layer Core Wood veneer floorboards are laid as normal floorboards, i.e. as a suspended floor provided the thickness is minimum 22 mm. They can also be laid as floating floors or as glued or nailed floors.

Figure 9 Wood veneer floorboards

FLOOR MATERIALS 9 Laminate floorboards Laminate floorboards are composite Top layer floorboards with either a chipboard or MDF or HDF core that is bonded to a film of wood effect veneer (lees than 2 mm thick) and covered with a laminated surface. It is not to be confused with wood veneer Bottom layer Core floorboards. The bottom side is covered with a counter veneer made of pvc laminate, paper or the like in order to prevent tensions and in order to maintain planeness of the board. See figure 10. Laminate floorboards are supplied with different surfaces, colours and patterns most of them imitating wood. Laminate floorboards with a thin layer of wood veneer are supplied in a variety of wood species and with surfaces imitating boards or parquet patterns. All veneered boards are supplied pre-varnished. Laminate floorboards and veneered laminate boards can be laid as floating floors or as glued or nailed floors

End grain wood blocks End grain wood blocks are rectangular Figur 10 Laminate wooden blocks made of oak, pine, spruce floorboard ± veneered or larch. The length of the blocks should not exceed 1.5 x the width. The blocks are available in thicknesses from 18 to 100 mm, see figure 11. The blocks are laid with fibres in vertical position. They are glued directly to the underlay using special glue. The best suited underlay is a rigid board material. The blocks may also be glued directly on a dry concrete slab. Blocks with a thickness exceeding 80 mm may alternatively be laid in sand. Good quality blocks may be used as floors in assembly rooms and dwellings. It does, however, require a good finish and surface treatment. As the surface on this type of floor consists of end grain it is very susceptible to moisture from the air as well as moisture from cleaning. It is therefore recommended to avoid direct exposure to moisture and to consult the manufacturer concerning moisture expansion and the possible need for dilatation joints. Figure 11 End grain wooden blocks

10 FLOOR MATERIALS SUBFLOOR Straightedge, 2 m

A prior condition to constructing a good wooden floor is the establishment of a high quality substrate ± only using materials Level deviation ± accepted value with adequate properties.

Floor battens Max. 5 mm Floor battens are made of solid wood or Straightedge, 2 m they may be made of laminated wood, see IT figure 12. Solid wood floor battens shall be Sideways deviation ± accepted value free of wane and should have a width of minimum 45 mm (planed dimension). Batten Laminated battens (for example Kerto) shall have a width of minimum 40 mm in order to eliminate the risk of splitting (when nailing or screwing). The battens should always be as long as possible as the best result will be achieved with battens in full room length Max. 2 mm (no joints). Standard lengths go up to 3.9 m and it may be possible to order battens up to Figure 13 Accepted tolerances ± floor battens 4.8 m. Battens should be planed on the side facing the floorboards. The battens must be Knot group sufficiently straight to meet the sraightness a+b+c=½ d requirements shown elsewhere on this page. After laying the battens the sideways deviation should not exceed 5 mm when d or compared to a 2 m straightedge (placed on 150 mm the concave side of the batten). Warping is only allowed to an extent whereby a batten placed loosely on Single knot

Maximum 1/3 Minimum 2/3

Figure 14 Floor battens ² requirements to knots

the floor and with one end fixed against the floor is leaving a gap of maximum 2 mm per every 2 m batten length, i.e. a batten with a length of 3.9 m is accepted to have a Figure 12 Floor battens: Sawn battens (1), strip warp corresponding to maximum 4 mm gap laminated battens (2), plywood principle laminated (at the other end) battens, Kerto (3). Reference is made to table 5 on page 47 for blocking up distances for the different types.

SUBFLOOR 11 The battens must be of a quality corresponding to the grading criteria applied in grading class T1. Consequently, single knots are only allowed to constitute 1/3 of the cross sectional area and groups of knots only ¼ of the cross sectional area, see figure 14. The best result is achieved when the moisture content corresponds to that of the floorboards. This will effectively reduce squeaking problems. The moisture content in the battens must never exceed 12 %, i.e. the average of moisture testing results should be maximum 12 %, and any single testing result must not exceed 14 %, see Appendix: Acceptance check. Packing pieces and cradle systems Materials used to chock up battens could be: (see figure 15) ‡ Plywood blocks, minimum 100 cm2, for example 100 x 100 mm or 80 x 125 mm ‡ Chip board blocks, minimum 100 cm2, for example 100 x 100 mm or 80 x 125 mm ‡ Hard or soft wood fibre board blocks minimum 100 cm2, for example 100 x 100 mm or 80 x 125 mm ‡ Plastic wedges or plastic towers ‡ Plastic or metal bases including accessory adjustable sub-system. When a higher block is required it is possible to use plastic towers (allows for more deflection), plastic or metal bases or a support made of fixed masonry or cast concrete blocks (no deflection) on top of which the final packing pieces are placed. Plastic wedges used as packing pieces shall have a documented approval concerning life expectancy and load carrying capacity ensuring long term durability. Exposure to excessive heating, Figure 15 Materials used as packing pieces and cradle systems: Plywood blocks (1), hard fibre for example from close contact with heating board blocks (2), chipboard blocks (3), soft fibre pipes, may reduce life expectancy board blocks (4), plastic wedges (5), wooden considerably. wedges (6), plastic tower cradles (7) and adjustable Plastic wedges of unknown origin and cradle system with plastic or metal bases (8 and 9). quality may decompose over time resulting in the settling of the floor which again may result in the need to substitute or relay the floor.

12 SUBFLOOR Soft blocks Soft blocks used in order to reduce the effect of impact sound shall be made of 12- 13 mm thick porous wood fibre boards with a density of 225-300 kg/m3 adhered to a pressure equalizing board made of minimum 12 mm plywood. The blocks shall have an area of minimum 100 cm2 for example 100 x 100 mm, see figure 16. The use of soft blocks with a smaller area or a lower density may result in the settling of the floor during use. Bitumen felt Bitumen felt is used under blocks in order to establish a sturdy underlay protecting the dpc (and being diffusion tight at the same time). It is recommended to use pieces of approximately 20 x 20 cm, see figure 16.

Figure 17 Insulation materials used for floating floors.

Bituminous felt may be used as dpc under floating or glued floors. The quality shall be PF 2000 (no sand finish) see figure 18. Insulation materials Insulation materials are used in the floor construction in order to improve sound or heat insulation, see figure 17. In batten or joist constructions it is recommended to insert 100 mm soft mineral wool between battens or joists in order to absorb sound. In floating floor constructions the function of the insulation is to prevent the transmission of impact sound from the floor to the structural floor and at the same time Figure 16 Soft blocks made of 12-13 mm porous to transfer load. With respect to impact wood fibre board adhered to minimum 12 mm sound it is recommend to use an insulation plywood placed on bitumen felt. material with resilient characteristics whereas considerations to strength and stability requires the use of a rigid insulation material. The required rigidity of the insulation material is determined on the bases of the expected load, the thickness of the insulation and type of flooring material.

SUBFLOOR 13 Moisture barriers Plastic foils used as moisture barriers must be at least 0.20 mm PE-foil (Polyethylene) in order to have sufficient strength to withstand strain during the construction period. Only foils with a documented diffusion tightness and durability should be used, for example complying with SPS Verksnorm 200/2001 (German standard). Caution should be taken that the foil is not perforated by a pointed concrete surface. Plastic foil is a good sliding layer for floating floors, particularly so when used in two layers or combined with flooring cardboard or similar products, see figure 18. Moisture barriers can also be carried out using bituminous felt, epoxy or special glues: ‡ Bitumen felt glued to the subfloor, see page 21. ‡ Cast asphalt with a thickness of 20 mm. ‡ Epoxy is applied in thin layers ± one at the time. An impartial documentation verifying that the product is efficient as a moisture barrier must be available. When applying, the prescribed thickness shall be observed as experience shows that the moisture barring ability is being drastically reduced when the layer thickness is too small - this may case subsequent damage to the wooden floor. ‡ Special glues - MS-glues ± are primarily functioning as a barrier retarding moisture penetration and only to a limited extend as an effective moisture barrier, see page 20. Figure 18 Examples of moisture barriers Top: (1) Combination: Plastic, felt and cardboard Middle: (2) PVC foil in different thicknesses/qualities. Bottom: (3) Bitumen felt PF 2000, no sand finish.

14 SUBFLOOR Flooring cardboard Flooring cardboard is used as underlay for flooring planks, parquet and flooring panels in order to reduce clatter. Flooring cardboard is a non impregnated cardboard with a weight of roughly 500 g/m2, see figure 19.

Foam plastic, cork sheet, or similar Foam plastic, cork sheet or similar products placed loosely under wooden floors serve as a pressure equalizer and sliding layer at the same time. The products also contribute to improving acoustics as they prevent clattering between floor and underlay and reduce impact sound. Some products also function as a moisture barrier eliminating the need for an additional moisture barrier, see figure 19. In order to secure that the products possess relevant characteristics and durability, only such products recommended by the floor manufacturer should be used.

Rubber cork/cork rubber Sheet rubber cork contributes to the reduction of impact sound and to improved flexibility in the floor. The effect depends on the thickness and composition of the product, see figure 19.

Figure 19 Clatter impact sound reducing materials for example flooring cardboard (1), flooring felt (2), foam plastic (3), plastic granulate (4), cork dust sheet (5), cork sheet (6) and rubber cork (7).

SUBFLOOR 15 Structural joists For further information concerning concrete Structural joists functioning as underlay for slabs reference is made to Concrete floor suspended floors shall be aligned forming a constructions elaborated by the Cement plane surface. Alternatively a plane surface Manufacturers (Cementfa-brikkernes shall be established by the application of an tekniske Oplysningskontor), 1994 additional plank/batten on top of or on the concerning workmanship ± concrete floors side of the structural joists. Additional and also GSO Floor Facts (GSO planks/battens shall have a minimum width of Gulvfacta) concerning levelling of floors. 45 mm in order to avoid splitting when nailing/screwing the floor. Screeds Joists should be chosen with consideration Screeds are used for the levelling of to the risk of warping; i.e. with minimum concrete slabs. Screeds may be based on tendency to warping, The need to reestablish cement, anhydrite or magnetite. Screeds can a plane surface may be minimized by using also be made from cast asphalt which at the laminated wooden joists (or HQL). same time will function as an effective The best result is achieved when the moisture barrier. moisture content in the joists corresponds to Screeds are normally laid in thicknesses that of the floorboards. In case the moisture of + 15 mm. The properties of the screed content in the joists is too high there is a risk depend on type and composition. In case of floor settlement due to shrinkage when the floor is a non-suspended wooden floor it the timber dries. The higher the joist is the is in most cases necessary to skim the bigger is the problem. The moisture content surface in order to obtain a sufficiently level in the joists must not exceed 13 %, i.e. the surface. average of moisture testing results should be For further information on screeds maximum 13 %, and any single testing result reference is made to GSO Floor Facts must not exceed 15 %. See Appendix: (GSO gulvfakta). Acceptance check. Sand Concrete slab Sand used as underlay for floating floors When a concrete slab is used as underlay for shall be well graded kiln dried quarts sand. nailed or glued wooden floors it is required All fractions of the grain curve must be to level the surface using a self levelling represented in order to secure sufficient compound, a smoothing compound or a packing after application and compression. screed. When wooden floors are glued to a concrete slab the surface must be cleaned of concrete slur as the slur layer does not have sufficient strength to absorb tension that may occur as a consequence of moisture movements in wooden floors

16 SUBFLOOR FIXINGS

A variety of fixings such as nails, screws, On the other hand, secret nailing has the glue and clips are used when laying wooden advantage that planks are pushed together floors. (manual nailing), see figure 20, page 18. When nailing hardwoods it is required to Nails, screws and staples pre-bore before nailing or screwing. The Planks in suspended floors are fixed to drill used for pre-boring must be slightly battens or joists using square nails, pin smaller in diameter than the nails or screws nails, screws, air gun nails or staples. used, for example a 3.5 mm drill used for 4.2 Wooden floors may be nailed from above mm screws. or using secret (hidden) nailing. When air Table 2 indicates dimensions of nails and gun nails are used only secret nailing is screws to be used for different board recommended. Nailing from above ensures thicknesses. As battens and joists do expand a better fixing of individual planks as it and contract in accordance with humidity, it allows for dimensional changes across the is not recommended to use fixings longer plank. than those indicated in the table as doing so may increase the probability of squeaking.

Table 2 Recommended dimensions on nails and screws for floorboards laid on battens or joists. The same screw dimensions may be used when fixing floorboards to an underlay made of chipboard, boards or the like. Hot dip galvanized nails provide the best grip in wood. Be careful not to use nails or screws longer than those recommended as doing so may increase the probability of squeaking when the battens or joists expand and contract. For direct fixing in concrete it is recommended to use special screws, for example Monta-flex. When in doubt, always consult the supplier of nails and screws. Plank thickness Nails Air gun nails Screws Chipboard in mm screws Ƒ-nails/finishing Staples T-pin nails Twisted Monta-flex nails nails screws 12-15 1.8x40 M-32 mm1) l.8x381) 4.2x45 F-14 2.0x382) F-14 2.0x453) 20-23 Solid 2.8x65 2,5x651) TS 2,3x652) 3) 4.2x45 5.0x45 pine/spruce 4030-2½"2) Solid 2.8x65 2.5x651) 4.2x45 5.0x45 hardwood; 4030-2½2) Wood veneer 2.5x55 N-50 mm 1) TS 2.3 x 652) 4.2x45 5.0x45 floorboards S-16 502) 25-26 3.1x80 4.2x45 5.0x55 28-30 3.4x90 4.2x55 5.0x75 35 3.8x100 4.2x75 5.0x75 1) Manufacturer: 2) Manufacturer: 3) For planks with a width between 100 mm Ottensten Unimerco and 150 mm

17 FIXINGS Nails Nailed from above Ssecret nailing Choice of nail type depends on wood species and floor type. As a rule of thumb square nails are used for manual nailing and twisted nails are used for air gun nailing in softwoods such as pine and spruce. Staples should only be used when recommended by the floor manufacturer. When fixing hard woods such as oak or beech, pin nails are used for manual nailing and T-pin nails for air gun fixing, see figures Figure 20 Fixing methods using nails or screws 21 and 22. Nailing should only be carried out using hot dip galvanized nails as experince shows Air gun nailing is used for certain that they have the best withdrawal floorboards but should only be used when resistance. Also, contrary to bare steel nails, recommended by the floor manufacturer. galvanized nails do not cause discolouration When nailing with an air gun it is which reduces such risk in light coloured important to press the flooring material delicate planks. hard agains the underlay in order to secure Traditionally wooden floors are hand proper fixing. Pressing with the air gun nailed, and this method is still considered itself is ± in most cases ± insufficient. the safest ± particularly so when laying solid floor planks in large dimensions in order to secure that the planks are pushed properly together and are securely fixed to battens/joists.

Staples T-nails

Ƒ nails Finishing Flooring nails nails (brads) Figure 21 Nail type for hand nailing Twisted nails

Figure 22 Nail types used for air gun.

18 FIXINGS Screws Wooden plug The choice of screws depends on the screwing principle adopted (from above or Floor secret). When screwing from above, ø 5 mm partially threaded chipboard screws are used. This is a type of screw which has no Screw thread immediately below the head and thus ensuring a better fit of the floor plank against the underlay. When applying secret screwing, special screws as for Batten example Monta-flex are used. This screw Figure 24 Secret fixing from above using has a high withdrawal resistance in wood, chipboard screws covered with a wooden plug. wooden boards and in concrete underlay, see figure 23. When screwing from above it is In sub floors made of chipboard the screws recommended to pre-bore a minimum 6 mm must be sufficiently long to penetrate the deep hole using a 10 or 15 mm drill in order chipboard. Chipboard screws or special to countersink the screws. Subsequently the screws like for example Plata-flex are holes are covered using a wooden plug used. made of off cuts using a wood plug cutter, The nailing and screwing of floating see figure 24. The plugs are glued fixing the floors should only be carried out when grains in the same direction as the grains in advised by the floor manufacturer. the flooring planks. When the glue is dry When using secret screwing it is a the plugs are cut off flush with the over side requirement that the floor planks have and the planks are sanded. thickness of minimum 12 mm. f

Wooden underlay Concrete underlay Planks fixed on structural sub floors made of Special screws for example Monta-flex, are chipboard, plywood or wooden boards may used when fixing directly on concrete. Pre- be screw- fixed provided the sub floor lays boring is required using a drill with a on beams or joists. The sub floor must have diameter slightly smaller than the screw sufficient thickness to secure satisfactory diameter, for example a 3.5 mm drill for adherence. 4.5 mm screws. The screw may be fixed directly into the pre-bored hole without the use of plugs.

Repairing squeaking floors Existing squeaking floors laying on battens or joists may be nailed from above using special nails such as annular ring nails or twisted flooring for example 3.5 x 55 mm Chipboard Monta- Plata-Flex screws Flex for 20-22 flooring planks and 3.5x 65 mm nails for 25-28 mm flooring planks.

Figure 23 Screw types

FIXINGS 19 Glue The fixing time is short for materials with a Glues used for the adherence of or gluing high absorption rate such as particle board together of floorboards must chosen and certain softwoods whereas materials consulting the recommendations issued by like bitumen cardboard and rubber cork the floor manufacturer in order to ensure allow for a longer fixing time. When that the glue is compatible with the wooden applying glue it is advisable to consider the floor and the underlay as well as being able glue¶s open time in order to ensure that the to resist whatever loads may occur. The laying may be carried out within the limit surface to be glued must be clean, dry and of the open time. auitable for gluing. Manufacturer¶s instructions concerning priming, Floor glue requirements consumption, application etc. must be From a wood technical viewpoint the glue complied with in order to secure a good should have the below listed properties: result. ‡ Low absolute water content in order to Gluing entire face avoid deformation of wooden floor When gluing the entire face of a wooden materials as a result of unilateral floor it is required that the underlay is level, moisture exposure on the underside. i.e. level deviations maximum ± 2 mm ‡ Ability to fill in such a way that contact along a 2 m straightedge and without can be established between glue and the craters or pointed edges in order to secure flooring material even in unfavourable proper contact between materials. situations, for example when there are Levelness of surfaces is described in detail small cavities in the underlay. in Appendix: Levelness ‡ Rapid fixation, maintaining the The glue to be used is so-called parquet block/plank in a fixed position in glue glue, either in the form of water based joint dispersion glue or MS glue, i.e. glue based ‡ Elasticity allowing the glue to absorb on Modified Silicone. The latter is more whatever movements there may occur in expensive but has the advantage that it is the glue joint free of water and to a certain extend ‡ Sufficient strength functions as a moisture barrier, see below. When gluing under difficult circumstances, The glue must not be too thin. for example on surfaces with little Wooden floors must not be glued until the absorption or the gluing of floor elements in residual moisture content in the underlay is sufficiently low, or until an effective large dimensions (planks) it is advisable to moisture barrier has been inserted, see more use one or two component glues without about moisture barriers on page 14. water. The use of such glues may, however, When using dispersion glues the residual cause work environmental problems as the moisture content must not exceed 65% bonding agent in most cases is based on relative humidity, whereas the similar limit polyurethane. for MS glues is 85% residual moisture content (does depend on glue brand), Gluing tongue and groove measured at temperatures between 17 and The purpose of gluing the tongue and 25 °C. groove joint in floating floors is primarily to The adherence of wooden floors shall take ensure that movement is being transferred place within a certain period of time, the so- from board to board (by creating a coherent called open time, in order to ensure floor surface). In this way the individual maximum bonding. The fixing time is blocks or boards function together, and normally approximately 15 minutes, but vertical forces may be accepted without depends on the materials to be glued and on unacceptable deflection. Further, the glued moisture and temperature conditions in the joint may serve to prevent the penetration of room. water when cleaning the floor.

20 FIXINGS PVA glue is normally used when gluing tongue and groove joints. In order to ensure maximum strength of the joint it is imperative to choose glue that is compatible with the wood species and also to ensure that the glue ³fills´, and is water resistant, in order to prevent damages caused by surface treatment and cleaning. The glue type normally used is a so-called ³winter glue´ (class D3).

Gluing bitumen cardboard When bitumen cardboard is used as a moisture barrier it may be glued to the underlaying concrete slab using parquet glue or a dispersion glue. When doing so the residual moisture content in the concrete must not exceed 85% (RH) and capillary rise of ground moisture must not occur.

Clips Some floorboards may be joined by the use of steel clips. Clips are used for floating floors. The clips are slotted into a milled groove at the backside of the floorboard and connect two neighbouring boards. In doing so, it is ensured that the boards can move individually in the horizontal Figure 25 As an alternative to gluing tongue and direction without being pushed apart and groove, floating floors may be laid using the total movement of the floor is reduced, mechanical joints in the form of steel clips(2) or see figure 25. click-joints(1).

Click-joints Specially designed for floating floors are a number of floorboards with a self locking tongue and groove. When the boards are laid they are ³clicked´ together and require no further fixing, see figure 25.

FIXINGS 21 when the air is moist and contracts when the WOOD AND air is dry. Hence, the moisture content and dimension of the wood will always adjust to MOISTURE be in equilibrium with the relative humidity and temperature of the surrounding air, see figure 26. Wood shrinks and expands in accordance The shrinking and expansion of wood in with air humidity and temperature. In order accordance with variations in air humidity is to get a good result, it is important to the reason why wooden floors shall be laid consider this particular characteristic when keeping a distance to surrounding building designing and constructing wooden floors. components allowing for expansion when the wood is exposed to moisture. This also Why does wood shrink? implies the need to lay wooden floors as The cellular walls in the living tree are late as possible in the building process saturated with water, and the cell cavities waiting for the building to dry out and thus are also filled with water. Wood shrinks reducing the amount of moisture present. when the water confined in the cellular See section ³The building site and walls dries out. The cellulose in the requirements related to moisture´. cellular walls has the property that it absorbs water from the air and expands Temperature approximately 20oC Pine Tem[ Fyr '.

]Dry;are f irrot vs.« danger mpe; egret i Konstructionstra; OvmStructural 0rrin; pak 'icvet timber

Kiln drying required OutdoorUien coveredlljTS ___ o\er- constructionsd; ikket OccationallyLejl ghed ;Ŷ heatedvis (ipvar- rooms" med; run Rooms with C'entral-central heating opvamede Radial Tangential rim shrinkageRaiialsvinc shrinkageTangenlials

Relative air humidity (per cent) Shrinkage (per cent) from freshly cut Figure 26 Graphic illustration of equilibrium moisture content (left) shows the connection between relative air humidity and moisture content in wood at approximately 20 °C, and the graph to the right shows calculation of shrinkage when changing equilibrium moisture content.

22 WOOD AND MOISTURE How does wood shrink? Shrinkage split All fibres in a freshly cut tree are water saturated. Later, as the wood dries there will Pith be dimensional changes (shrinkage) more or less corresponding to the reduction of water. Similarly, wood will expand when exposed to moisture. Expansion and contraction are Pith characterized by taking place in three dominant directions, see figure 27. Shrinkage split ‡ Tangentially ± along the annular rings Figure 28 Items with pith are subject to (circular in the trunk) shrinkage splits depending on the position of ‡ Radially- Perpendicular to the annual the pith in the board. rings (along pith rays) ‡ Axially- Along fibres (longitudinal direction) How much does wood shrink? It is often necessary to be able to calculate by how much a certain dimension is changed as a result of varying moisture content in the wood (which, as explained Tangentially above, will vary in accordance with varying air humidity). As a realistic average, which may be applied to a number Radially Axially of commonly used wood species, it may be assumed, that the change of 1 % in wood moisture content results in a dimensional shrinkage of approximately 0.15 % (1.5 mm/m) radially, and approximately 0.30 % (3.0 mm/m) tangentially. When calculating expansion the same values may be applied. In case the trunk is cut tangentially or radially, see figure 29, it is possible to apply Figure 27 The three dominant directions for the two mentioned shrinkage percentages shrinkage and expansion of wood directly. In reality planks may often be cut in between the two positions and it is Normally, the tangential shrinkage is therefore required to apply a medium approximately twice as big as the radial shrinkage value of 0.22% (2.2 mm/m) shrinkage. The axial shrinkage is only Tangential corresponding to somewhere between one conversion tenth and one twentieth of the radial shrinkage and for the same reason it may be disregarded in most cases. Items with pith are subject to one or more shrinkage splits extending from surface to pith and as a consequence they are not fit to be used for flooring, see figure 28. Radial cuts There may be considerable differences between the density of the bottom part and Figure 29 Shrinkage and expansion of wood the top part of a trunk and thereby also big depends on conversion principle applied/annual variation in shrinkage and moisture ring position. conditions.

WOOD AND MOISTURE 23 How moisture influences wooden 10-board measurement floors When laying a wooden floor it is important When choosing wooden floor type and also to ensure that the floor can absorb when constructing the floor it is important movements caused by moisture. This is to consider the inevitable dimensional often done by use of the so-called 10-board changes caused by seasonal variations in measurement. air humidity, see figure 30. The10-board measurement is defined as the It is not possible to avoid gaps between expected width of 10 boards when exposed floorboards, but it is possible to predict the to maximum moisture. This is typically in size of future gaps simply by choosing the the autumn where an average of 13 % right floor. In this context the term gap is moisture content may be expected in the used to describe the space between floorboards. When laying the floor with neighbouring boards or blocks in the floor. lower moisture content, for example kiln The size of the gap may be reduced as dried to 8 % it must be ensured that a small gap is established between the boards/blocks follows: for example by placing thin spacers between ‡ Use narrow boards in stead of wide boards the boards. The 10-board measurement because the size of the gap corresponds to shall be controlled at regular intervals board width. during the laying of the floor. ‡ Choose products with small dimensional Wood veneer floorboards and soft wood changes as a consequence of changed air floorboards, for example pine, are normally humidity. laid without observing the 10-board ‡ Control climate, for example by the use of measurement. air humidifiers in office buildings during the winter in order to avoid the drying out The 10-board measurement depends on: of wood. ‡ Width of boards ‡ Avoid the use of floor heating systems and ‡ Maximum expected air humidity. radiation heating systems placed in the ‡ Wood species (expected change in board ceiling. width) ‡ Annular ring orientation (radial or Grams of water per m3 air tangential conversion) RH % The 10-board measurement is mainly used when laying floors type: RH out ‡ Hardwood parquet boards (nailed) RH in ‡ Solid parquet blocks with T&G glued to the sub floor. ‡ Parquet blocks (nailed)

IN Spacers OUT Until recently it has been common practice to observe compliance with the 10-board measurement simply by basing the laying on Jan. Mar. May Jul. Sep. Nov. experience whereby the contractor would Feb. Apr. Jun. Aug. Oct. Dec. check the prescribed 10-board measurement Figure 30 Typical variation in the relative humidity at regular intervals during laying procedure. (RH) inside and outside during the year. The relative In order to ensure uniform spacing it is humidity is at its maximum inside from August to recommended to use so-called spacers, i.e. October, and at its lowest from December to March. small pieces of plastic with a thickness (SBI direction 178).The RH in office buildings and corresponding exactly to the gap required in the like is often considerably lower that indicated in order to comply with the prescribed 10-board the graph. measurement. The use of such spacers will make the constant checking procedure redundant as the spacers will ensure compliance with the prescribed 10-board measurement.

24 WOOD AND MOISTURE Examples

Some examples showing to what degree The total width of the17 gaps has been moisture influences dimensional measured by the use of feeler gauge and changes of a wooden floor. is 48 mm which corresponds to 2.4 % across the 2 m floor. Example 1 An average shrinkage of 0.22 % for When a floorboard has been stored for every 1 % change in moisture content some time at approximately 20°C and will result in (2.4 %: 0.22 %) = 11 % exposed to approximately 78 % RH it will change in moisture content of the boards have a moisture content of approximately in order to cause a shrinkage of 2.4 %. As 16 %. If the RH is changed to 40 % and the actual moisture content is measured the temperature is maintained at 20°C the to 7 % it can be concluded that the wood will discharge water to the air and moisture content was 7 + 11 = 18 % the moisture content will adjust to when the boards were laid. approximately 8 %, see figure 26. Thus, the moisture content will be reduced by Example 3 8 % which will result in the following A floor consists of 100 mm wide shrinkage: floorboards with a moisture content of 8 %. The floor is laid in a room with 23 °C Tangential shrinkage: 0.30 x 8 = 2.4 % and 40 % RH, which corresponds to Radial shrinkage 0.15x8 = 1.2 % equilibrium moisture content of 8% in Suppose the board is cut tangentially with the wood. 10 boards will under these a width of 100 mm and 16 % moisture conditions give a width of 1000 mm, content, it will, at 8% moisture content provided they are laid without gaps. have a width of: 100 - (0.3 % x 8 x 100) = It is, however, assumed that the RH in 97.6 mm. the room will increase to 65-70 % during the summer period corresponding to a Suppose the board is radially cut, the moisture content of 13 % in the wood. width will be: 100 - (0.15 % x8 x 100) = Exposed to these conditions each board 98.8 mm. will expand by (0.22 % x 5 % x 100 mm) Suppose the board is cut somewhere in = 1.1 mm (cf. example 1). In order to between radially and tangentially the allow for this expansion it is required to width will be: 100 - (0.22 % x8 x 100) = lay the boards with a gaps of 1.1 mm 98.2 mm. between neighbouring boards, i.e. 10 For wood species (or products) with boards will require a total width of (1000 small dimensional changes caused by mm + 10 x 1.1 mm) = 1011 mm, which moisture variations, the shrinkage may in this case will be the 10-board be reduced by 50 %, whereas the measurement.. shrinkage in wood species with larger During winter, the temperature may be dimensional changes may be increased 23 °C and the RH 25 % corresponding to a by 50 %. drop in wood moisture content to 6 %. The shrinkage in the longitudinal Using summer conditions as starting point direction is normally less then one tenth this means that a board during the driest of width shrinkage. period will shrink approximately (0.22 % Example 2 x (13 - 6) % x 100) = 1.5 mm. It can thus A traditional wooden floor has 18 boards be expected that a floor laid under above per 2 m. The boards are laid without mentioned assumptions will have 1.5 mm spacing. After some month the gaps wide gaps between the boards during the between the boards will vary in size from driest period. 0 to 5 mm.

WOOD AND MOISTURE 25 Moisture protection - requirements

Design and construction assumptions

Avoiding excessive exposure to moisture or Perimeter drain exposure to moisture during a longer period are preconditions for the use of wood in floor Flat terrain constructions. Neither must the floor be exposed to excessive drying out. Such exposures may result in the risk of rot or dry rot when the moisture content exceeds 20 % (weight), and it may also cause undesirable dimensional changes and deformations. In the subsequent section it will be demonstrated how to construct wooden Intercepting drain floors avoiding moisture problems. In office buildings, where the production of moisture Sloping terrain is normally at a minimum, there is a risk of extreme drying out during periods with frost. Figure 31 Adjustment of site profile ensures the This may result in shrinkage and as result of leading away of surface water and drainage is carried out to the extend necessary. this in larger gaps in wooden floors, particularly so in floors constituting large planes without or with limited possibilities Paved terraces shall be established with a for movement. In some cases it may be minimum slope of 1:40 in order to preserve necessary to use humidification during the the slope also in the event where the coldest and driest periods of the year in order pavement settles, see figure 31. to avoid damages. In order to ensure correct construction of Ground supported floor wooden floors, particularly with respect to When constructing a ground supported floor, moisture, it is advisable to follow the measures must be taken to prevent the guidelines laid down in SBI-Direction 178: absorption of ground moisture. This may be Moisture insulation of buildings. See also done by the insertion of a capillary breaking SBI-Directions 184: Heat insulation of layer. Residuous moisture in the concrete buildings and 189: Single family houses ± slab must be prevented from entering the insulation, moisture protection etc. offering wooden floor by the insertion of a dpc on top concrete examples of constructions meeting of the slab. s in this dpc must have an current requirements in terms of moisture overlap of minimum 200 mm. The joints protection and heat insulation. should also be additionally secured by the use of tape or butyl rubber sealant strip. Outside the building The dpc is lead close to the wall and an The terrain must slope away from the building airtight joint is established between the dpc in order to allow for the effective draining and the dpm in the wall (if any). This also away of surface water. In flat terrain the secures against the penetration of radon, see slope shall be minimum 1:50. In sloping figure 32. terrain it is required to level the ground on the In order to avoid condensation of side of the building with the highest terrain moist air from the room on the top side and it is recommended to establish an of the dpc, it is required to place at least intercepting drain at the intersection between the naturally sloping terrain and the adjusted terrain.

26 MOISTURE PROTECTION - REQUIREMENTS dpm dpm Wooden floor dpc Wooden floor Insulation dpc Insulation

Minimu Minimum m slope slope

Figure 32 The placing of dpc and dpm in Figure 33 The placing of dpc, dpm and insulation constructions with floating floors on ground in constructions with suspended floors on floor supported slab. batten on ground supported slab.

half the insulation under the dpc. In practice this is most often done by placing half the insulation under the concrete slab, see figure 33. Ventilation When carrying out renovation works, it is often only possible to place insulation on top of the dpc. In such instances it is Cut outs in Diffusion tight recommended to use maximum 50 mm skirting board insulation in order to avoid the risk of floor covering' condensation on the topside. Required additional insulation will, in this case, have to be carried out as foundation insulation. Heating pipes under wooden floors must be insulated separately and effectively in order to avoid the drying out of floorboards. Also, measures should be taken to place the pipes on the warm side of the insulation. When a diffusion tight floor covering (for example vinyl or linoleum) is used on a Insulation suspended floor on floor battens it is required to make cut outs in the skirting board in order to allow the floor Figure 34 Establishing additional ventilation in construction to adjust to the humidity of the floors on floor batten covered with a diffusion tight air in the room. In this case a cavity of floor covering (for example vinyl or linoleum). minimum 30 mm must be established on top of the insulation material in order to allow the room air to ventilate the underside of the floor.

MOISTURE PROTECTION - REQUIREMENTS 27 Ground supported floor in unheated Dpm buildings Wooden floor The temperature in unheated buildings, such Insulation as holiday cottages, will, during winter, be higher in the ground under the building than it is inside the building. Hence, the moisture flow will, during winter, go from the ground through the ground supported floor and into Dpc the house. In such buildings it is important Slope Ventilation to establish the moisture barrier (dpc) minimum correctly. No moisture sensitive materials 1:50 must be placed under the dpc and joints in Dpc the dpc as well as joints to other building components must be airtight in order to avoid the risk of condensation on the underside of a diffusion tight layer. This is also the reason why the use of diffusion tight floor coverings should be avoided in unheated or occasionally heated buildings Figure 35 The placing of dpc, dpm and ventilation with a ground supported floor. G openings in constructions with wooden floors on joists (crawl space deck). Crawl spaces In crawl space decks consisting of wooden external walls or capillary rise of ground floors on joists it is particularly important to moisture. maintain the humidity of the air in the crawl The external basement wall shall be spavc at the lowest level possible. It is drained and the drain must be connected to recommended to establish a dpc at the the perimeter drain in order to prevent the bottom of the crawl space in order to prevent local occurrence of water pressure against the ingress of moisture from the ground the external wall. The outer side of the below. It is also required to establish basement external wall shall have a double sufficient ventilation. Figure 35 shows the coating of liquid bitumen applied on top of a size of and the placing of necessary rendered or rough cast surface or by the use ventilation openings. of specially designed PVC drainage sheeting In order to prevent the ingress of radon it is preventing the penetration of moisture. recommended to place a dpm under the With respect to moisture it is advisable to wooden floor. carry out heat insulation on the outer side of the wall and on the outer side of possible Basements drainage sheeting. There is always a risk connected to the Under the basement floor it is required to laying of wooden floors in basements. One establish a capillary breaking layer thing is certain: If the basement is not dry preventing the absorption of moisture from the wooden floor will not last!! If moisture is the ground. The best solution is to place the present, the floor will be exposed to heat insulation under the concrete slab. This excessive dimensional changes. Before insulation may ± depending on the choice of laying wooden floors in new buildings all materials ± be carried out as a combined moisture must be ventilated away until the heat insulating and capillary breaking layer, basement is sufficiently dry. In unheated see figure 36. basements the RH will, especially during Provided the basement construction is summer, reach 90 % which is too high for carried out along the above described the use of wooden floors. A modest heating recommendations and, provided it is of the basement may reduce the RH to 75% heated, it is possible to lay a wooden floor during summer provided there is no following the same guidelines as those moisture penetration through leakages in applicable to a normal ground supported floor. It is required to place a dpm on the concrete slab before laying the wooden floor. Joints in the dpm shall overlap by minimum 200 mm and the joint between dpm and wall shall be airtight.

28 MOISTURE PROTECTION - REQUIREMENTS Storey partitions Dpm In order to eliminate the risk of problems originating from construction moisture it is Insulation recommended to place a dpc on top of new Wooden floor concrete or light weight concrete deck storey partitions. It is not required to place a Slope, dpc on top of existing and dry deck minimum constructions. 1:50

- Dpc Moisture requirements on building site. The dimension of the wood depends on the moisture content which again depends on the relative humidity (RH) and temperature of the surroundings. As the relative Wooden floor humidity changes with the seasons and also Dpc with the use of the room so will the Insulation Insulation dimensions of the wood change. It is very and drain important to consider this aspect when designing and laying wooden floors. In order to avoid unnecessary moistening it is important to lay the floors as late as possible in the building process. The building shall be closed, dry and heated Drain before laying the floor. All such works as may cause the generation of moisture, for Figure 36 The placing of dpc, dpm and insulation example plastering and basic paint work in constructions with a floating wooden floor on shall be terminated before the flooring starts. storey partitions and on ground supported floors The RH in the building shall be in in basements. equilibrium with normal RH for the season, i.e. 35-65 % relative humidity at When renovating old houses it is often a approximately 20°C. wish to establish wooden floors. In such When concrete or light weight concrete cases it is required to carry out a moisture elements are used it will, in most cases, be insulation of the constructions. The floor necessary to wait for a couple of months construction principles are similar to those before laying the wooden floor. If used in new buildings. In case the room necessary, it may be required to use height is low, it is possible to use a floating dehumidifiers. Before laying wooden floors floor construction with a moisture and on new concrete or light weight concrete pressure resistant insulation as the load decks it is required to measure the moisture carrying underlay. The dpc can be placed content in the deck, see Appendix: between insulation and wooden floor or Measuring moisture content in concrete. under the insulation (in case the quality of Insulation materials etc. shall be dry. In the insulation is inferior to or equals 50 mm case blocking up has been carried out using mineral wool lambda class 39). For further concrete or brickwork such elements must information concerning the renovation of be cured and dry. old basements, reference is made to SBI- In case the building has not been properly Direction 178. dried out, the relative humidity will be very high and the wood will expand after the laying ± and later, when the wood dries out, the gaps between the boards will be very wide. In case there is too little space around the floor the expansion may cause the floor to ³pop up´ or in the worst case to push out surrounding walls.

MOISTURE PROTECTION - REQUIREMENTS 29 When investigating the moisture conditions before laying wooden floors on concrete it is Check list – laying wooden floors not suficient only to measure the relative ‡ The relative humidity in the building humidity of the air but it is also required to shall be between 35 and 65 %, measure the moisture content in the (depending on the season) and the concrete. The reason why is that ventilation temperature approximately 20°C. may reduce the relative humidity of the air ‡ The building must be closed and the without reducing the moisture content in the heating system operational and in use. concrete. ‡ The moisture content in concrete and In case wooden floors are to be used under light weight concrete shall be in conditions where it is only required to secure equilibrium with the relative humidity of against moderate construction moisture from the air for the season in question, i.e. the underlaying concrete, i.e. a pore moisture pore moisture content shall be 35-65 % content of 60-90 % RH, it is possible to avoid relative humidity. In the case of concrete moistening the wood by using a PE-foil or light weight concrete elements it may minimum 0.20 mm thick. This dpc shall be take a couple of months to attain laid with minimum 200 mm overlap on top of equilibrium. In situ cast concrete may the moist concrete before laying the wooden require much more time. floor. ‡ Insulation materials etc. shall be dry ‡ When blocking up is made of masonry Flooring materials - moisture or concrete it must be cured and dry. requirements ‡ A dpc ± for example a 0.20 mm PE-foil Floorboards and parquet blocks are shall be laid before laying the floor in normally supplied kiln dried and wrapped in order to protect the floor against construction moisture. a strong PE-foil with a moisture content of 8 ‡ The wooden floor material shall have a ± 2 %. 2/3 of the lot should have moisture moisture content of 8 ± 2 % of which content between 7 and 9 %. The moisture 2/3 of the lot should have a moisture content in joists, floor batten and blocks content between 7 and 9 %. should, as far as possible, correspond to the ‡ When wooden floor materials are kiln moisture content in the supplied floor. dried to specifications they should not At the point of laying the average moisture be unpacked before the laying. content in floor batten should not exceed 12 ‡ The moisture content in joists and floor % and in joists it should not exceed 13 %. In batten should correspond to the practice this means that the average value of moisture content in the wooden floor. 12 % (13 %) must be complied with and no The average moisture content should single values of moisture content in excess of not exceed 12 % in the case of battens 14 % (for battens) and 15 % (for joists) are and 13 % in the case of joists and no accepted see Appendix: Acceptance check. single value must exceed 14 and 15 % In cases where it is not possible to get a respectively. supply of flooring materials with correct ‡ In case the wood is not supplied kiln moisture content, it is imperative to deliver dried, time must be allowed for the the flooring materials well in advance wood to obtain equilibrium with the allowing sufficient time for acclimatization, moisture and temperature conditions i.e. to attain equilibrium with the temperature existing in the room. and moisture conditions in the room before ‡ Wooden materials, glue, caulking the actual laying. This process may take compounds and similar accessories should be acclimatized for at least 24 several weeks ± even when the boards are hours before use. This could be done by stacked using piling sticks. Laying a wooden storing such materials inside the room floor with excessive moisture content may where they will be used. result in the occurrence of larger gaps between the boards when the wood dries out.

30 MOISTURE PROTECTION – REQUIREMENTS maximum temperature to which the floor FLOOR HEATING may be exposed and the heating system shall be constructed in such a way that this temperature is not exceeded. Floor heating systems are primarily used in In floors where boards or blocks can move order to avoid the use of radiators and in independently it must be expected ± at least order to achieve a good distribution of heat during the heating season ± that the gaps inside the room. Traditionally, floor heating between the boards will be slightly larger systems have been used in floors with than normal. This is caused by the heating ceramic tile covering in bathrooms , but of the floor which will cause the drying out during recent years an increased used has of the wood and as a consequence larger been observed in all other rooms of the shrinkage across the boards, see example house and also in other floor types , for below. Considering this shrinkage it is example in wooden floors. advisable to use materials with as little In new and well insulated houses it is, shrinkage as possible. under normal circumstances, possible to heat a house using a floor heating system only. In older houses where the insulation Example: does not live up to current requirements it is 22 x 125 mm pine floorboards are laid on floor normally required to use supplementary batten. During the year, the moisture content heating sources, for example radiators in will vary between 6 % during winter and 13 % order to meet the heat demand. during summer. It is anticipated that the gaps between the boards are totally closed during It should be noted that wood is a relatively the summer. When, in winter, the floor is most well-insulating material. As a result wooden dry there will be a gap of (13-6) x 0.22 % of floors, to the touch, feel more comfortable 125 mm = 1.9 mm. In case of floor heating the (warmer) than other floor coverings ± even average temperature will increase from 21 to without floor heating. Thus, from the point 30°C and the moisture content during winter of view of comfort there is no need to use will drop to approximately 4 %. Thus the gap floor heating in wooden floors in well- will increase to (13 - 4) x 0.22 % of 125 mm = insulated houses. 2.5 mm. When installing floor heating systems under wooden floors the following conditions shall be observed: One consequence of using floor heating in ‡ The temperature shall be low in order to floors on battens is the heating of the avoid the drying out of the wood. The battens. As a consequence the battens will suppliers normally require that the surface dry out more than usual. For this reason it is temperature does not exceed 25-27°C. particularly important that the battens are ‡ The heat distribution below the floor shall dry when laying the floor as the extra be even, not only to ensure maximum drying out of the battens will cause comfort, but also to achieve sufficient additional shrinkage and thereby increased heat radiation. It is therefore important to risk of squeaking floors ± see more about lay heating pipes or cables in such a way this on page 73. It is therefore required to that no major variances in temperature ensure that the battens are dried until they occur on the surface. have the same moisture content as the floorboards, i.e. a moisture content of Only such materials and construction 8 ± 2 %. In order to achieve this it is often principles, including floor heating systems, required to stack the battens for a period of as recommended by the supplier of the 8-14 days inside the room where they will wooden floor should be used. In this context be used. Notice that prefabricated battens the supplier of the floor is required to produced from kiln dried wood may also supply information concerning the require additional drying in case they have been stored for a longer period in an

FLOOR HEATING 31 unheated warehouse or at the timber Floor heating systems merchants. Figures 37-39 show three construction Floating floors which are glue-jointed in principles using light constructions where it is the T&G will not have the same problem possible to control the floor heating with a time with larger gaps between the boards during constant of 1-2 hours, i.e. it is possible to adjust the winter. On the other hand, the gap the room temperature fast, for example when between the surrounding walls and the the room is subject to insolation (sun through floor may be bigger. In case the floor is windows) or when there is a need to reduce the loaded with heavy furniture along the walls temperature during night. there is an increased risk that the floor may split, see more about this on page 74. Heating pipes between battens or between Whether the floor heating system is water- joists borne or electric, it is possible to obtain an When heating pipes are placed between even heat distribution under the floor as battens or joists it is common practice to shown in figures 37-40. clip the pipes into so-called heat Before laying the wooden floor it is distributing panels placed in close contact important that all such works that may with the underside of the floor in order to generate moisture, for example masonry work obtain a good temperature distribution. or paintwork, are terminated and the floor The heat distributing panels are produced heating system must have been working for a with a groove into which the pipe fits, see period of at least 14 days. The heating system figure 37. It is required to use pipes with a is switched off at least 2 days before laying diameter corresponding to the size of the the floor. groove in order to ensure good contact Heating systems used in wooden floors between pipe and panel. The pipes should are purpose made systems, i.e. the systems not touch the underside of the floor. are constructed with independent heating It is common practice to use an circuits supplied with an automatic device intermediate layer such as flooring controlling the floor temperature. If cardboard or felt in order to reduce possible, it is recommended to use a preset clattering and squeaking, see figure 37. temperature control device which does not allow for temperatures above the level Heating pipes on top of battens or joists recommended by the floor manufacturer. When the heating pipes are placed on top of Temperature adjustment should take place the joists or battens it is required to place an gradually as sudden temperature changes additional layer of boards or battens may cause splitting of the wood. perpendicular to the direction of the joists or In general, it is not recommended to lay battens. This layer serves as underlay for the wooden floors on top of existing floors with heat distributing panels. Otherwise the old floor heating systems which are not construction is carried out as described supplied with automatic control devices for above, see figure 38. temperature control. Boards are used in cases where chipboard is used as a structural floor serving as underlay for a floating wooden floor. The dimension of the chipboard is defined in accordance with the distance between the joists of floor batten as the additional layer of boards is not considered to be load carrying. Battens/planks are used as underlay for the heat distributing panels in cases where the floorboards are laid parallel to joists or floor battens. In this case the additional layer is load carrying and the battens/planks shall be dimensioned in accordance with table 5, where the blocking up distance will be equal to the distance between the floor batten/joists. The blocking up distance my be reduced by inserting additional floor batten or joists.

32 FLOOR HEATING Heating pipes on heat distributing panels Heating pipes in floor heating slabs. Floor heating slabs consist of one layer of insulation material (usually polystyrene) Floor boards or and heat distributing metal sheets. The floor parquet boards heating slabs are supplied with ready made grooves fitting the heating pipes. The slabs are placed on top of a structural underlay and Intermediate layer the pipes are placed in the gooves. An intermediate layer (flooring cardboard or felt) is placed between the slabs and a pressure distributing subfloor made of chipboard on top of which a floating floor may be laid, see figure 39.

Wooden floor possibly on top of Insulation pressure distributing sub floor Joists Boards (25x100 mm) on Intermediate layer battens c/c 600 mm Heating pipes on floor heating slab Figure 37 Heating pipes placed on heat distributing panels which again are placed on top boards placed on structural joists or floor battens. The heating pipes cross the joists in the zone outside the end of the joist in order not to weaken the joist by cutting into it. Floorboards are screwed or nailed. Chipboard as structural floor Intermediate layer

Heating pipes on heat dpc Insulation distributing panels Floating wooden floor Concrete slab Intermediate layer

Figure 39 Heating pipes in »Floor heating slab«, i.e. insulating slabs made of polystyrene supplied with heat distributing metal panels. An intermediate layer of flooring cardboard or felt is placed between the heating slab and the floor above in order to reduce impact sound. The floor is laid as a floating floor.

Addtional boards carrying heating pipes Damp proof course The purpose of placing a dpc in wooden floors Figure 38 Heating pipes on heating distributing with floor heating is to secure the wood against panels placed on structural joists. Here shown with undesired moistening. The placing depends on chipboard as structural floor and floating wooden floor. May also be carried out with structural the construction in question and also depends on battens (replacing additional boards) and where in the building the floor is placed. It is floorboards. recommended to consult with SBI-Direction 178 or to ask advice from the floor supplier.

FLOOR HEATING 33 Embedded heating pipes and cables When embedding heating pipes or cables in concrete there should be a cover layer of Wooden floor minimum 30-70 mm on top of the pipes or the cables in order to achieve an even heat distribution and the wooden floor should be Glue placed as close as possible to the underlay, Levelling compound, minimum 10 mm see figure 40. An efficient dpc, for example bitumen felt, should be placed between the concrete and the wooden floor in order to Electric-cables prevent the transportation of moisture (released from the concrete by the heating) Levelling compound. from concrete to wood. It is difficult to adjust the heat radiation rapidly because of the heat accumulating capacity of the concrete which causes the Figure 41 Electric cables in levelling compound time constant for this type of floor to be as should be so placed that they are covered with minimum 10 mm levelling compound to ensure high as 12 hours. even heat distribution. Heavy constructions used to be considered an advantage as they were able to accumulate energy during periods with sun and release Electric heating mats/electric cables placed the energy again during the night in levelling compound. With the thickness of insulation applied Electric-based heating systems may also be today this capacity is no longer interesting. . fitted using levelling compounds. The total height of this construction is very low. The Wooden floor cables may be placed directly on top of an inorganic underlay or placed on a wooden Intermediate layer based underlay with minimum 5 mm Possibly dpc levelling compound between the cable and Concrete slab with 30-70 mm cover layer underlay. In order to ensure an even heat distribution the thickness of the levelling compound on top of the cables should be at least 10 mm, see figure 41. It is recommended to use a fibre reinforced levelling compound which is capable of Reinforcement mesh resisting foreseen temperatures. Possibly insulation One significant difference between electric Concrete slab systems and water borne systems is the fact that the electric system gives a fixed effect Figure 40 The embedding of heating pipes in and as a result high temperatures may occur concrete gives an even heat distribution. The under thick carpets, furniture etc. In order to placing of dpc and insulation depends on the avoid excessive heating it is recommended construction in question ± consult experts in the only to use such cables and mats which are field. capable of supplying the heating required with the lowest effect possible and never 2 Maximum effect for floor heating exceeding 100W/m . A low effect provides systems: The effect should never the same comfort as a high effect, but will of 2 course result in a slower regulation of the exceed 100 W/m temperature. In practice, this is not a problem as the temperature is normally set to a certain surface or room temperature once and for all.

34 FLOOR HEATING Aspects related to energy When placing floor heating It is imperative to follow carefully the under wooden floors – instructions issued by the floor manufacturer when laying and using wooden floors with remember: floor heating ± including recommendations ‡ Floor heating may only be used concerning the types of floor heating and together with such products suitable for constructions which may be used, and what the purpose and approved by the temperatures the floor may be exposed to. supplier. Under furniture and floor coverings, for ‡ The floor heating system shall ensure an example under book cases and carpets with a even heat distribution on the floor good heat insulating capacity the floor surface. temperature may be higher than the ‡ The floor heating system shall be temperature in other parts of the floor. This supplied with a preset temperature may cause extra large gaps between the control device which does not allow for floorboards during winter. temperatures above the level recommended by the floor manufacturer. The limited surface temperature ‡ Only such floor heating systems as obtainable also determines the effect which recommended by the floor may be released by a floor heating system. manufacturer may be used. As a guideline it may be reckoned that a ‡ The need for supplementary heating from floor heating system may release an effect as radiators is likely in older houses. expressed in the following formula: ‡ Floor batten/joists shal be dry in order to Released effect = 10 x (t - t ) W/m2, avoid squeaking. f r ‡ Avoid the laying of wooden floors on where tf is the surface temperature of the top of old floors with floor heating floor and tr is the room temperature. without automatic temperature control. When calculating with this formula using ‡ Laths placed as underlay for heat the most commonly occurring surface distributing panels are countersunk between joists or floor batten temperatures we get the results shown in ‡ In electric-based flooring systems the table 3. effect must not exceed 100 W/m2. ‡ In water-borne heating systems the pipes must not touch the floorboards. Table 3 Released effect in wooden floors with commonly occurring surface temperatures and with a room temperature of 21°C. In comparison the energy need for new single family houses insulated in accordance with BR-S 98: 45 W/m2

Maximum surface temperature Surface temperature °C Effect W/m2 The surface temperature in the wooden 25 °C 40 floor must not exceed 25-27°C. 26°C 50 Depending on thickness this corresponds 27°C 60 to the following temperatures on the underside of the wooden floor: ‡ 22 mm thickness: 33-34°C Best in well insulated houses ‡ 14 mm thickness: 30-32°C The heating with floor heating is only ‡ 10 mm thickness: 28-30°C sufficient in new and well insulated houses. When remodelling houses it is recommended The temperature difference between to use supplementary heat supply in addition upper- and underside depends on floor to floor heating, for example in the form of thickness, wood specie and material composition (solid/laminated).

FLOOR HEATING 35 radiators. This is due to the fact that the ET ROOMS insulation in older houses is normally W inferior to present requirements and as a consequence the effect needed is higher. Because of its beautiful texture it has Larger energy consumption become very tempting to use wood as In general larger energy consumption may flooring material in wet rooms. However, it be expected when using floor heating is against regulations to substitute compared to the use of radiators. This is the traditional ceramic tiles or PVC floors with reason why the building regulations BRS 98 wooden floors, cf. B&B-Direction 200 require additional insulation in ground ³Wet rooms´. The reasons are several: supported floors and in storey partitions Generally speaking, wood is not suited to facing the outside or facing ventilated crawl withstand constant exposure to water or spaces when such floors are supplied with excessive humidity as such exposure may floor heating. In these constructions the cause the growth of fungi and ± worst case maximum U-values are: s scenario ± rot or dry rot. The combination ‡ In multi-storey of elevated humidity and high temperature ± buildings: common to bathrooms ± is very productive 0.12 in stead of 0.15 to the growth of dry rot. ‡ In single family houses Wooden floorboards are narrow and as a and the like.: consequence there are many joints. Add to 0,.12 in stead of 0.15 this that most floors are laid as so-called ³ships plank´ with caulked joints (elastic Also floors above heated rooms should be caulking compound). supplied with insulation under floor heating As a rule of thumb, the water tightness in systems in order to prevent the undesired wet rooms must not be based on the use of heating of the room below and in order to elastic joints because such joints are not long save energy. term watertight. Even in cases where a watertight membrane has been used there is a risk that water may penetrate the joints which may cause the growth of fungi and or bad odour. Seen in this light, wooden floors in wet rooms are only accepted in the following cases: ‡ When fixed on top of a finished, approved and consequently watertight floor, i.e. inclusive floor covering of ceramic tiles or PVC. ‡ In areas of the room not frequently exposed to water. ‡ On the condition that the wooden floor may be removed again without damaging wet room constructions.

In general it is not recommended to use wooden floors in wet rooms because of the increased risk of obnoxious smells, growth of fungi and possibly rot or dry rot in case of excessive humidity.

36 WET ROOMS Under all circumstances it must be considered that wooden floors will have a Wooden floors in wet rooms shorter lifetime compared to other surfaces ‡ Are beautiful- but only serve as decoration used in a bathroom and as a result they must ‡ Cannot substitute ceramic tiles or PVC be substituted more frequently. flooring as watertight underlay. ‡ May cause risk of fungi attack etc. It is an obligation to inform the client, that ‡ See guidelines for the use of wooden floors the risks of inconveniences related to the use in wet rooms on page 38. of wooden floors as supplementary floor covering, is entirely his own responsibility. Should the client still want to use wooden floors, such floors must only be laid in less exposed areas of the wet room, and, in order to minimize the risk of inconveniences, observing the guidelines indicated in the summary on page 38, figure 42. The wooden covering shall be kept well away from areas particularly exposed to moisture, for example shower stalls, bath tubs and floor drains, se figure 41. No pipe penetrations are accepted in the wooden floor and it is not accepted to establish a floor drain, see figure 43 and the guidelines on page 38. The wooden floor must be treated and maintained in accordance with manufacturer¶s instructions. As the use of wooden floors in wet rooms increase the risk of bad odours, fungi attack etc., it is recommended: Figure 43 It is not accepted to construct wooden ‡ To immediately remove free water from floors in wet rooms with floor drains or pipe the floor surface penetrations. ‡ To pay special attention to any signs of or symptoms, which may indicate water penetration, moisture or the presence of fungi?

Figure 42 Wooden floors are only accepted in wet rooms provided they lay on top of an approved watertight wet room floor and observing a distance requirement of minimum 500 mm away from shower stalls, bath tub and floor drain.

WET ROOMS 37 ASPECTS RELATED Guidelines for the use of wooden floors in wet rooms TO SOUND ‡ The wet room shall have an approved and completed floor, i.e. inclusive a floor covering made of PVC or ceramic Floors on battens tiles. In case there is a demand to the reduction of ‡ Wooden floors are only allowed in impact sound on wooden floors it is impact class L (low) with few baths per required to place a piece of soft material, for day and of short duration and efficient example a porous wooden fibre with a ventilation after use. Low impact class is thickness of maximum 13 mm and glued to particularly found in single family a pressure distributing piece of plywood hoses, holiday cottages and the like, cf. see page 12. The thickness of the soft B&B-Direction 200 ³Wet rooms´ material shall be equal in all blocks used for ‡ The wooden floor must have a plain blocking up. underside with as few cavities as The packing pieces shall be fixed to the possible along T&G joints and the battens using toe-nailing, i.e. a nail entering boards should not be supplied with stress the batten on the side and continuing at an grooves on the underside. angle into the block or wedge, see figure 58. ‡ The wooden floor is ³full-face glued´ to The nail must not enter the soft material. the underlay in such a way that cavities, which may contain water, are eliminated. An alternative packing method to wooden ‡ In order to prevent the penetration of blocks (combined with soft blocks) is the use water, all joints between boards and of plastic wedges. When using wedges made along adjoining walls are caulked with a of hard type plastic, the impact sound level mastic caulking compound. may be increased by 0-4 dB. Always contact ‡ The joints must be inspected at regular the wedge manufacturer for further intervals and repaired in case leaks are information concerning impact sound detected. reduction. ‡ Wooden floor and materials used - Battens and floorboards shall be kept at a including adhesives, caulking distance of minimum 10 mm away from compounds and underlay - must be surrounding walls and pipes penetrating the compatible. floor. ‡ A distance of minimum 500 mm When electric cables and heating pipes between the floor and shower stall, bath run under the floor it is required to keep a tub and floor drain must be observed, distance of 10 mm between cable / pipe and see figure 42. batten. Notches made for pipes or cables ‡ No pipe penetrations or floor drains are shall also observe the 10 mm rule. accepted in the wooden floor (neither is In case a floor continues under the it possible as no flor drains have been threshold, it is recommended to establish a approved for the use in wooden floors) 20 mm joint between floorboards and see figure 43. between joists under the threshold, see ‡ Accepted species are teak and species figure 44. with similar characteristics in terms of The use of chipboard or plywood resistance and durability when exposed to moisture. drastically increases the ³stiffness´ of the ‡ Good heating and efficient ventilation is floor as compared to floorboards. As a result required in order to keep the room as the sound diffusion from the floor plane will dry as possible and thereby prevent the be increased and the impact sound in attack of fungi. surrounding rooms will increase as will also the drum sound effect in the room in question. It is difficult to reduce the drum sound effect in rooms with wooden floors. Some reduction may be achieved by inserting mineral wool or sand in the cavity between the battens/joists.

38 ASPECTS RELATED TO SOUND Minimum 10 mm clearance around pipes

Minimum 10 mm clearance

Minimum 20 mm Minimum 10 mm from wall Insulated joint under threshold Insulation Batten Minimum. 10 mm above pipes Soft blocks

Floating floors Figure 44 Construction details ensuring impact Floating floors with an elastic intermediate sound reduction in floors on battens. layer in the form of an insulation material will reduce the impact sound level. The thickness and the elasticity The latter also discusses possibilities of (compressibility) of the layer greatly improving sound insulation in old storey influences the potential impact sound partitions by adding supplementary floor reduction. Large thickness and large coverings on top of existing coverings. compressibility give high impact sound reduction. The use of thin insulation ± below 10 mm ± requires a completely level substrate. Roughness in the underlay Minimum 10 mm Wooden floor caused for example by a pointed concrete from wall surface may be pressed into the insulating layer and may cause contact between the Sub floor Intermediate layer floor and the underlay, hereby increasing reducing impact sound the risk of sound bridges, see figure 45. The floors must not touch the surrounding walls or pipes penetrating the floor. Risk of sound bridges caused by pointed concrete The efficient sound reduction in floating floors very much depends on correct Figure 45 Construction details ± impact sound constrution. For further information reduction in floating floors. concerning sound insulation reference is made to SBI-direction 172, Sound insulation in buildings - newer buildings and to SBI-direction 173, Sound insulation in buildings - older buildings.

ASPECTS RELATED TO SOUND 39 JOINTS Dilatation joint

The purpose of establishing joints in wooden floors is: 1) to absorb expansions, Dilatation joint 2) to transfer forces and 3) to establish a characteristic subdivision of the floor Dilatation joint Insulation joint surface. around column Differentiation is made between dilatation joints and insulation joints see figure 46. The purpose of dilatation joints is to absorb moisture and temperature caused Dilatation joint Dilatation joint movements between materials in the floor between columns plane, figures 48-49. Dilatation joints are normally only found in floating floors. Suspended floors on battens or on joists as well as glued or nailed floors do not Insulation joint normally require dilatation joints, provided around heavy fixed Dilatation joint they are constructed correctly. furniture Insulation joints are used to separate floors from adjacent building components such as columns and walls, see figure 50. Insulation joints may function as dilatation Figure 46 The placing of dilatation and insulation joints at the same time. joints in floating floors. Joints shall be so designed that they are capable of absorbing such movements as Areas where large movements may be may be expected in the floor plane in expected, as a consequence of moisture question. The number and position of joints variations, require several wide joints of are determined by type of floor high quality. Movements must not be construction, load and expected moisture hampered in floors with irregular geometry variations as well as geometry of the room and with columns penetrating the floor, see and the wood species used. figure 46. In case dilatation joints have been Subdivision of the floor plane should, as established in the sub floor, such joints must far as possible, be carried out in rectangular be repeated in the finished floor itself. fields in order to allow for equal size of Mastic caulking compounds and soft expected movements in both directions. synthetic rubber profiles are used for Under normal circumstances it is possible to smaller joints. Metal profiles are primarily construct floor planes without joints up to used when excessive movements are 8x12 m, where 12 m is the longitudinal expected in the floor plane. direction of floorboards. When constructing larger floors it is advisable to consult the Floating floors floor manufacturer. Large mechanic loads, for example from book cases or reception desks in open space End grain wood block floors offices may impede the movements of Expected moisture related movements in floating floors, see figure 46. This fact may end grain wood block floors is greater than reduce the size of floor areas constructed in most other wood floors. Reference is without joints. The use of hard and strong made to the guidelines issued by the floor joints against adjacent floors or building manufacturer concerning field sizes. Such components may hamper the free movement guidelines should be observed. of the floor plane.

40 JOINTS Caulking compound Possible adjustment Joints and caulking compounds of joint depth Elastic polysulphide-, MS-polymers - or polyurethane compound are used in wooden floors. With respect to compressibility and wear the compounds Floor batten must have a hardness corresponding to 40-65° Shore A. In joints along wall a more flexible compound is used. In order to avoid the adherence to the bottom of the joint it is required to use slip tape, see Caulking compound Caulking compound- figure 47. Caulking compounds in Slip tape- Adjustment of dilatation - and insulation joints must joint depth always be supported from below, see figures 48-50. Therefore ± never caulk joints without backing. The width of the joint should be minimum 8 mm and maximum 15mm. Along wall, columns etc. the joints may have a width up to 30 mm. In as far as it is possible, the cross section Loose metal tongue -Joint support ± of the joint should be square. When using for example a loose batten thick floorboards this may require adjustment of the joint depth for example by Figure 48-50 Dilatation ± and insulation joints the insertion of pressure resistant, acid free shall always have support from below, for cardboard EPDM profiles or polyester example by the use of a metal bar serving as a loose tongue between to floor planes (49) or a needle felt, see figures 47 and 50. loose batten under floors on battens (48 and 50). Documentation showing compatibility between applied caulking compound and wood species must be available. This is Documentation must also be made particularly important when using species available on the compatibility between oil, containing oil, for example teak. In such varnish and other remedies for surface cases the supplier¶s instructions concerning treatment. priming must be followed carefully because Joints must be carried out in the extraction of oil and resin from the consultation with the supplier of the wood may cause the forming of blisters in caulking compound in order to ensure the caulk. correct choice of compound and primer. As a rule of thumb all adhering surfaces must be cleaned and primed according to Caulking supplier¶s directions. The caulk groove compound must have clear cut and sharp edges. . Wooden surfaces bordering the joint must be covered with tape before caulking. Slip tape Floor which requires sanding may be sanded with course sandpaper before Caulking caulking. Fine sanding takes place when the compound caulking is hardened and after removal of excessive compound (by cutting). Adjustment of joint For further information, reference is made depth to guidelines issued by FSO.

Figure 47 Placing of bottom stop, for example slip tape. The joint depth should be adjusted in order to establish a square caulk profile.

JOINTS 41 Movement profiles Metal cover strip Metal cover strip Joints designed with metal profiles or extruded rubber profiles are used in areas where large movements are expected or where adherence between the materials on the two sides of the joints is not accepted see figure 52. A movement profile can be made with metal anchoring legs (for example Figure 51 Open joints covered with metal profile aluminium) connected to a movement zone (cover strip). Is applicable to all floor types, see made of soft synthetic rubber as shown in more details in section ³Laying guidelines´ (page figure 52. Such profiles are available for 58) wood / wood joints and for wood joining other flooring materials. Special designs Movement profile with also exist for the joining of floors with visible anchoring legs different height levels. The profiles are produced in a number of special designs, for example with angles for corners and in T-shape. The EPDM rubber profiles are also produced in a number of different designs, for example angle corners or T- shapes. The rubber is normally renewable. Always use metal profiles or extruded Movement profile with rubber profiles where the free concealed anchoring legs movement of the floor is desirable

Ships plank joint / groove for fillet Ships planks are made by moulding a groove next to the tongue on the top side of the boards. The groove is filled with a contrast material in order resemble the original Figure 52 Top: Visible standard profile fixed caulking. This contrast material can be a from above. Best solution for dilatation joint in caulking compound, a wooden fillet, or a glued / screwed floors. rubber fillet, see figure 53. Ships plank Bottom: Concealed standard profile anchored to joints can also be established by the the sub floor before laying the wooden floor. The profile is countersunk into the subfloor in order to insertion of loose fillets between the boards establish a plane surface. see figure 49. When ships plank joints are made using a caulking compound it is important to notice that the cross section should be square similar to other joint between floorboards. Bottom stop and priming is also important. Course sanding of the floor takes place before caulking, and fine sanding only takes place after proper hardening of the caulking compound. When ships plank joints are made using wood or rubber fillets, the fillets are placed in the moulded groove where they are mechanically fixed and / or glued in a specially created key. Wood fillets are glued with water resistant PVA-glue. Rubber fillets should be glued with glues as specified by the supplier. Rubber fillets Figure 53 may be joined at ends using cyanoacrylate Examples of grooves using caulking glue (10-seconds glue). and loose fillet

42 JOINTS LAYING INSTRUCTIONS

The choice of underlay for wooden floors shall be adjusted to the type of floor in question and shall always be sufficiently rigid and plane in order to ensure the correct laying of the wooden floor.

Covering Under normal circumstances a wooden floor should always be covered immediately Figure 54 Batten or joist distances as well as after laying in order to protect the floor blocking-up distances are measured form centre to against damages during the remaining centre (c/c) construction period. Materials used for covering could be cardboard or wooden The laying of battens fibre boards. As a minimum requirement, the battens Areas with much traffic, door steps and should be planed and straightened on one staicases, which are particularly vulnerable, side and be in one piece. should always be covered with cardboard The first row of battens is placed at a or hard wood fibre boards. The wood fibre distance of 50-80 mm from the wall. Along boards are fixed by taping to the walls, where heavy loads normally occur, extra underlaying cardboard using an appropriate battens are placed as shown in figure 55 tape in order to avoid the undesired (unless otherwise instructed by the entering of dust and dirt particles under the manufacturer). The battens are placed with the covering, where such particles may cause desired distance and chocked with blocks, dents and scratches in the finished floor. On wedges or similar packing pieces in order to door steps and staicases the fibre boards adjust the height, establishing a plane surface may be fixed using small pins along edges. across the battens. Packing pieces must rest on a plane surface in order to secure stability. Wooden floors on battens or joists Floors on battens are normally laid on a substrate of concrete or light weight concrete, but may also be constructed on top of a Extra batten wooden sub floor. When laid on concrete it is recommended always to lay a dpc before laying the floor in order to avoid problems originating from the presence of construction Extra batten approx. 70 cm moisture or from capillary rise of ground moisture. The dpc could for example be minimum 0.20 mm PE-foil laid with minimum 200 mm overlap at joints. Packing piece

Distances between supports The support distances for suspended floors on battens are indicated in tables 4 and 5. The distances indicated ensure a reasonably stiff floor preventing annoying vibrations Figure 55 Placing of battens. Notice the extra batten when walking and preventing the along walls and the staggered packing of battens. inconvenient inclination of furniture and equipment caused by floor deflection. The support distance depends on the chosen thickness of materials and the expected load, see figure 54.

FLOORS ON BATTENS 43 Table 4 Batten and structural joist distances calculated from centre to centre The distances ensure against undesired deflection and vibrations. When a calculation indicates a dimension somewhere in between the indicated distances, the nearest lower distance should be applied. Floor material Batten or joist distance Minimum thickness in mm Dwellings etc. Smaller shops Assembly rooms or the like Floorboards 20 mm tongued and grooved boards 520 420 360 22 mm tongued and grooved boards 600 490 420 25 mm tongued and grooved boards 720 590 500 28 mm tongued and grooved boards 860 700 600 30 mm tongued and grooved boards 950 770 670 Structural sub floors* 15 mm Plywood glued in T&G 400 350 320 18 mm Plywood glued in T&G 600 520 480 22 mm Flooring chip board glued in T&G 600 520 480 * Guiding values

Wooden based blocks used as packing pieces should always be glued together in order to avoid displacement. The packing Wooden floor piece material should be fixed to the batten with a nail in order to avoid displacement Batten Toe-nail during the laying and later during the use of the floor. The fixing also helps preventing squeaking floors. The usual nailing method Wedges is ³toe-nailing´, i.e. a nail entering the batten on the side and continuing at an angle into the block or wedge, see figure 56. When soft blocks are used with the Figure 56 The packing of battens using wedges purpose of sound reduction, care must be taken to ensure that the nail does not enter the soft material, see figure 57. The density of the soft wood fibre board shall be 225- 300 kg/m3 and the size shall be minimum Wooden floor 2 100 cm , for example 100 x 100 mm in order Batten Toe-nail to avoid settlement in the floor when loads Soft board are applied. The plywood block placed on packing piece Plywood packing top must have the same dimension, see 100x100 mm piece 100x100 mm figure 57. Possibly bitumen In basement floors and on ground felt 200x200 mm supported floors extra care must be taken in order to avoid the absorption of moisture. It is therefore recommended to place a piece of Figure 57 Chocking-up battens using wooden block bitumen felt (200 x 200 mm) below the packing pieces and posiibly bitumen felt. When soft packing pieces. blocks are used with the purpose of sound reduction, care must be taken to ensure that the nail does not enter the soft material

44 FLOORS ON BATTENS Floor on battens

Wooden floor Batten Toe-nail Toe-nail Plywood packing Insulated pipe Soft board packing Plastic wedges

Possibly dpc Wooden joist Wooden deck element or /wooden wooden storey partition stringer Figure 59 Packing of battens by the use of high plastic wedges creates sufficient space for the running of pipes. Figure 58 When packing battens on a wooden storey partition the position of the packing pieces must be aligned and in line with structural joists below and comply with distances indicated in table Batten Insulated pipe 4. When battens are positioned perpendicularly to structural joists, it is required to choose a batten Incision dimension which allows for a chocking-up distance at least corresponding to the distance between the structural joists.

Chocking-up on top of structural joists is Minimum shown in figure 58. The overall height of 10 mm the packing pieces must allow for a gap of distance minimum 10 mm between batten and to batten Soft block underlay. In case pipes or other installations are placed under the floor, there must be at Figure 60 When incisions are made in the least 10 mm between such installations and battens, for example for pipes, it is required to establish additional supports on either side of the batten. the incision. Pipes under the floor shall be well- insulated in order to avoid the undesired heating of the wooden floor, see figure 59. In case incisions are made in the battens, it is required to establish an additional support on either side of the incision, see figure 60. Battens shall always be supported at butt joints (end joints), see figure 61. Butt joints must not be aligned under the same floorboard.

FLOORS ON BATTENS 45 In renovation work, where it may be Spacing of packed bases and impossible to avoid the aligning of butt Battens used as underlay for wooden floors joints, it is required to reinforce the joints shall be sufficiently stiff in order to ensure with fishplates on either side of the joint, that it feels safe to walk on the floor. using for example 12 mm plywood Table 5 shows the normal spacing fishplates minimum 300 mm long. The between packed bases (lmax in mm) for a quality of the plywood used must, as a number of cross sectional dimensions and minimum, correspond to American C-D or types of battens better. The spacing shall be reduced by at least When joints are made without the use of 10 % along batten ends. This also applies to fishplates it is required to support each end battens butt joints and possible stress relief of adjoining battens using packing pieces cuts, see figure 62. with a minimum length of 125 mm In dwellings, offices and light industry (measured along battens). The packing the point load Q is set to 2 kN, for smaller pieces are placed roughly 50 mm from the shops Q equals 3 kN, and for assembly ends of the battens see, figure 61. rooms and bigger shops Q is set to 4kN. The distance between packed bases The spacing between supports and depends on batten dimension, as shown in packed bases indicated in tables 4 and 5 table 5. The spacing between packed bases may be used in normal rooms according to shall be reduced at batten ends and batten mentioned user classes. In cases where the joints, see figure 62. floor is temporarily exposed to loads When, in exceptional cases, stress relief exceeding the loads normally occurring in cuts are established, it is required to place the user class in question, it is required to packed bases under each such cut and the reduce the distance between supports and spacing between bases shall be reduced packed bases in accordance with the according to figure 62. expected extra load, for example from electric wheelchairs, trucks and heavy book cases. Fishplates minimum 300 mm

Spacing between packed bases Maximum 100 mm

Figure 61 An additional support shall always be ÷ 10 % established when battens are butt jointed or joined with fishplates.

The spacing between packed bases is reduced by minimum 10 % at batten ends.

Figure 62 The distance between packed bases shall be reduced at batten ends, at batten joints and where stress relief grooves are established. The reduction normally corresponds to 10 % of normal spacing.

46 FLOORS ON BATTENS Table 5 Spacing of packing pieces and cradle systems under floor battens in main floor area. Along ends of battens the spacing shall be reduced by 10 %, see figure 62. Design assumptions for table 5 are described on page 48. Batten Dwellings, offices and Smaller shops Assembly rooms and dimension light industries larger shops height x width (Q = 2 kN) (Q = 3 kN) (Q = 4 kN) ______mm Sawn Laminated Sawn Laminated Sawn Laminated 1 2 battens battens battens1 battens2 battens1 battens2

1 The indicated distance is allowed provided the wood used has a stiffness corresponding to K18 (E0 = 9000 MPa) 2 The indicated distance is allowed provided the laminated wood used corresponds to L30 (E0 = 12000 MPa) or to L40 (E0 = 14000 MPa). The stiffness in laminated products depends on number of layers, wood quality and production method. Supplier will inform about Elasticity module upon request. 3 Sawn battens produced from solid coniferous wood and graded in accordance with grading class T1 will comply with strength class K18 requirements. 4 Laminated battens produced (glued together) from planed coniferous staves will normally achieve strength/stiffness properties equivalent to strength class L30. 5Laminated battens type LVL (Kerto and others) normally have) v strength/stiffness properties equivalent to strength class L40.

FLOORS ON BATTENS 47 Design assumptions used in the calculation of spacing between packed bases and other supports under floor battens:

Battens used as underlay for wooden floors Maximum support distance lmax for supports shall be sufficiently stiff in order to ensure under central part of a batten with the that it feels safe to walk on the floor. width b, the height h and the effective E- The below mentioned formulas describe the module Es and exposed to point load Q can acceptable distances between batten supports be determined by the use of this formula: depending on load, cross sectional 3 3 l = l0mm bh Es/Q dimensions and wood quality (E-module). max The formulas are defined on the basis of The distance is rounded off to whole 10 traditional norms, but adjusted to loads and mm units. Along ends, and in rare cases of stiffness requirements listed in DS 410:1998 stress relief cuts in battens, it is required to Code of Practice for Loads for the Design of reduce the support distance by 10 %. Structures and in DS 413:1998. Code of The constant 10 mm has been chosen in Practice for the structural use of timber such a way that lmax becomes 600 mm The code values for point loads and surface for a sawn batten with cross sectional loads in different user classes (for example dimensions of 45x45 mm and normal dwellings, offices, assembly rooms) are stiffness Eo = 9000 MPa (Structural assumed to represent the correct mutual timber class K18). relationship between loads. In practice, the Table 5 shows the support distances for a only factor of real interest is the deflection number of cross sectional dimensions and caused by the point load. code stiffness with maximum support The stiffness of normal structural timber is distance lmax in central floor area as a usually much higher than the mean value function of point load, wood quality and Eo stated in DS 413. In order to achieve batten dimension. In dwellings, offices uniform stiffness in battens made of and light industry the point load Q = 2kN, traditional structural timber and in battens in smaller shops Q = 3 kN and in assembly made of processed materials with a rooms and larger shops Q = 4 kN. predefined stiffness, the effective E-module It should be noticed that battens are not used in the following will be defined as: part of the load bearing structure and as such are not subject to code requirements. Es = Eo12000 MPa for Eo < 12000 Mpa Consequently, it is irrelevant whether Es = Eo for Eo • 12000 MPa calculations show whether or not the battens will be able to accept assumed point loads in DS 410:1998.

The laying of floorboards ± nailed or minimum 10 mm between wall and screwed. floorboard must be observed. In larger Before laying the floor it is required to pack rooms it is necessary to increase the distance, batten supports in order to establish a level depending on room dimensions and floor surface across the battens. This is controlled product in accordance with manufacturer¶s by the use of a straightedge and a spirit instructions. level or by laser levelling, see figure 63. Temporary distance blocks are placed The first row of boards is laid with the between the first row of boards and the wall groove facing the wall. The boards are in order to avoid the displacement of the aligned using a building line. A clearance of board during the laying process, see figure 63.

48 FLOORS ON BATTENS Distance blocks

Extra batten

Straightedge

Extra batten Dpm - optional Batten

Figure 63 The battens must be completely level and stable. The boards are aligned using a building line and clearance is established along walls.

Floorboards nailed / screwed from above. Tongue Distance blocks, When boards are fixed using visible minimum 10 mm nailing /screwing, the nail / screw is placed Min. 50 mm at a distance corresponding to ¼ of the board width from the grooved edge of the board. When boards are particularly wide, i.e. more than 200 mm, the visible nailing /screwing requires two nails / screws in Groove every board, see figure 64. In the case of secret fixing from above, the boards are fixed using countersunk Batten wood screws. Screw holes are plugged with wooden plugs, see page 19. Otherwise the floor is laid in accordance with Tongue Groove guidelines applying to floors with secret nailing / screwing.

Figure 64 Floorboards - screwed / nailed from above. In case the boards are wider than 200 mm it is required to use two screws / nails according to distances indicated.

FLOORS ON BATTENS 49 Floorboards with secret nailing It is recommended to blunt the nail point in Floorboards may be fixed using secret order to avoid splitting of the wood. The nailing or secret screwing. When boards are head of the nail may be used to drive in the screwed, pre-drilling is always required. previous nail. Doing so, the nail head The first board is nailed to the batten from becomes slightly rectangular. Placing the above using secret nailing in the tongue, see long side of the nail head parallel to the figure 65. The visible nail in the first board board will reduce the risk of splitting. is places roughly 20 mm from the grooved Guiding dimensions for nails are side of the board. Finishing nails are driven indicated in table 2, page 17. Boards are into the wood with a nail set, and the holes nailed in all battens. However, it is not are filled with adequate filler. recommended to nail at a distance shorter The tongue side is fixed using secret than 50 mm from the end of a board, see nailing from the upper side of the tongue. figure 64. The nails are placed at an angle roughly 45- Subsequent boards are laid and knocked 60° in relation to the upper side of the together using a hammering block or a floorboard. Nails are driven into the wood. hammering rail making observing the 10- It may be necessary to pre-drill in order to board measurement, see figure 67. In some avoid damaging the tongue, see figure 66.er cases a board oof-cut may be used as hammering block. In other cases it is required to use a special hammering block in order to avoid damaging the profile.

Hammering block

Floor board Batten

Figure 65 Fixing the first board and nailing Figure67 The boards are knocked together using principles in remaining boards. a hammering block or a hammering rail. Packing pieces

Cupped and warped boards can be difficult to force in place alone by nailing. The use of wedges as shown on figure 68 may help solving this problem forcing the board into place. Clean-cut board ends must be joined along batten centreline. Butt jointed boards 2.8x65 mm 3.1x80 mm should have the same orientation of annular 3.4x90 mm 3.4x90 mm rings in order to avoid the cupping in opposite directions when the boards dry out, Figure 66 Placing and dimensions of nails see figure 69. Boards are square cut in order when nailing through the tongue (secret to ensure a tight joint. In order to further nailing). secure a tight joint both cuts may have slight inclination away from the joint, see figure 69.

50 FLOORS ON BATTENS Butt joint along batten centreline

Wedges 2 bays Board

Wooden block ± fixed Batten or joist to batten with screws Figure 70 Butt jointed boards must span across minimum 2 bays. Not more than every third board Figure 68 Curved boards may be forced in place should be joined on the same batten. by the use of wedges.

Bevelled cut

No unsupported joints

Unsupported butt joints with T&G end joints Board

No unsupported joints 2 bays between butt joints Avoid different orientation of annular rings Figure 71 Boards with T&G unsupported butt Figure 69 Butt jointed boards must have similar joints may be used in dwellings or similar. orientation of annular rings, and it is an advantage Unsupported joints must not be used in first and to bevel the cut slightly in order to establish a last board and not in more than every third board tight joint. within the same bay ± never in neighbouring bays. Boards and joints of this type must span across two bays at least, and not more than every third board should be joined on the End joints within the same bay may only same batten, see figure 70. occur in every third board, i.e. there must Boards supplied with T&G in the ends be two continuous boards between every may be joined without support from unsupported butt joint, see figure 71. beneath, so-called unsupported butt joints. Unsupported butt joints must not occur in This type of joints must always be glued. neighbouring bays, and no unsupported When using boards with T&G unsupported butt joints may occur in the first and the butt joints, the laying is continued using the last row. Unsupported butt joints should off-cut from the previous row as starter not be used in floors exposed to loads piece in subsequent row. exceeding those occurring in dwellings.

FLOORS ON BATTENS 51 The last board is designed as shown in figure 72. It is sometimes difficult to fit in the last board, and to solve this problem it may be expedient to chamfer the upper lip of the groove on the side facing the centre of the board. It is also possible to bevel the side of the board facing the wall. In case the last board is very narrow it may be necessary to lay the last two boards simultaneously. They are glue-jointed before the laying, see figure 73. In case the supplier recommends Maximum. 250 mm observation of the 10-board measurement it is required to comply with the said measurement. The 10-board measurement Figure 74 Door with threshold and floorboards indicates the cover width of 10 boards. The perpendicular relative to door opening. Notice 10-board measurement is indicated as an maximum joist distance. interval, for example 1293 ± 1298 mm within which random check measures of the width of 10 boards must fall.

Packing

Figure 72 Designing the last board. Figure 75 Packing of threshold ± floors with different levels.

The last two boards Wedge- The measurement depends on the width of can be glued / the individual boards, the expected highest nailed together. humidity during use, and the chosen wood species.

Doors with threshold The floorboards meet under the threshold. There should be a clearance of 20 ± 30 mm between ends of floorboards in the door opening ± depending on extend of Figure 73 Laying the special-made last board. adjoining floors. When boards are placed perpendicular to door opening, as shown in figure 74, the joints between the

52 FLOORS ON BATTENS Metal cover strip

Figure 76 Floorboards may continue through Figure 77 Joint covered with metal strip. This door openings when the door has no threshold. solution is used when floorboards are positioned This solution should only be used in smaller perpendicularly or parallel in relation to each other. rooms. boards should be aligned on either side of Pipe penetrations the threshold. The floor planes in Holes for pipes shall have a diameter 20 adjoining rooms should have the same mm larger than the pipe going through the level. In case this is not possible, the hole in order to allow for the independent threshold should be packed in order to movement of the floor, and in order to align it with the level of the highest floor, ensure that there is no contact between see figure 75. floor and pipe. When floors are fitted after pipe Doors without a threshold installation the hole is cut as illustrated in In case the doors do not have a threshold it is figure 78. Once the floorboard is in place possible to let floorboards continue through the cut out block is glued back into the door opening ± when the floorboards are position, and the hole is covered with an positioned perpendicularly relative to the escutcheon. opening, see figure 76. Wedge with When floorboards continue through a bevelled door opening it is required to design the sides width of the joints along walls as if the floor were in one room, measuring the width from wall to wall through the door opening. When floorboards in one room are positioned perpendicularly relative to floorboards in adjacent room, as shown in figure 77, it is required to establish a joint with between the two floors. The width of the joint should be 15-20 mm depending on the size of adjoining floors. If needed, the joint may be covered with a flat or curved metal cover strip. The strip should only be fixed to one of the floors and must not be countersunk to become flush with the floor Figure 78 Cutting a hole for pipe penetration. The surface. wedge has bevelled sides ensuring a tight fit in the This solution may also be applied in opening. cases where the floorboards in both rooms are positioned parallel to the door opening. In this case the joint will accept movements from both floor planes.

FLOORS ON BATTENS 53 Floating floors with coherent wood or concrete sub floors on Floating floors are normally laid on structural top of which the wood floor is laid out and floors made of concrete, lightweight concrete maybe glued. The sub floor has a pressure or wood. When laid on concrete or distributing function and, being so, the floor lightweight concrete it is recommended covering does not need to be a suspended always to lay a moisture barrier in order to floor, but can be made of short block parquet avoid construction moisture or ground or mosaic parquet, see figures 79-83 moisture from entering the floor. The moisture barrier should consist of minimum 0.20 mm PE-foil laid with minimum 200 Glue Wood floor mm overlap in all joints. In case it is required to lay the wood floor very soon Wood flooring panel after casting the concrete it is required to use a very tight moisture barrier, for example bitumen felt glued to the concrete slab and with airtight joints, see Gluing bitumen felt, page 21.

Underlay and intermediate layer Intermediate Before laying intermediate layers it is layer required to level the sub floor creating a Moisture plane surface, for example by the use of a barrier smoothing compound. Deviations from Concrete planeness should be less than ± 2 mm when compared to a 2 m straightedge. Type of intermediate layer is chosen with Figure 79 Floating floor constructed with parquet consideration to establishing a reasonably blocks or parquet boards glued onto a wood rigid floor which does not shake flooring panel laid on a thin intermediate layer unnecessarily when walked on, and does not cause the inclination of furniture or Glue equipment due to deflection. Maximum Wood floor deflection should not be more than be 2.5 mm. Wood flooring panel The preferred materials for intermediate layers are: Expanded polystyrene type EPS 150 or EPS 250, hard mineral wool batts, porous wood fibre boards, robust geo Moisture textile in more the one layer, foam plastic barrier sheets with air bubbles and special mats based on rubber and cork. When using compressible intermediate layers like Hard mineral wool and polystyrene, it is insulation recommended to insert a pressure Concrete distributing board, for example 22 mm floor chipboard. Figure 80 Floating floor constructed with parquet blocks or parquet boards glued onto a wood The floor plane flooring panel which again is laid on hard Floating floors are made in such a way that the insulation. floor constitutes one coherent floor plane able to move independently in relation to the underlay. The floor plane may be constructed

54 FLOORS ON BATTENS T&G floorboards joined with steel clips Glue Wood floor Intermediate layer Concrete slab

Wood flooring panel Moisture barrier Hard insulation Moisture barrier Hard insulation Concrete Concrete

Figure 81 Wooden floor glued on top of a floating Figure 83 Floating floor made with pressure concrete slab. Notice that the concrete slab must distributing flooring panels laid on top of hard be completely dry and plane before gluing the insulation. The floor cover is T&G floorboards wood floor. joined with steel clips and laid on a thin intermediate layer in order to reduce clattering.

Intermediate layer Wood floor Wood floor Wood flooring panel Intermediate layer

Moisture barrier Moisture barrier Hard insulation Concrete Concrete

Figure 82 Floating floor made with pressure Figure 84 Floating floor made with glue-joined distributing flooring panels laid on top of hard wood veneer floorboards laid on a rigid insulation, The wooden floor (glue-joined wood underlay, for example concrete, and with a thin veneer floorboards) is laid on a thin intermediate intermediate layer, which may function as a layer in order to reduce clattering. sound reducing layer and as a moisture barrier at the same time.

Floating floors may also be constructed by gid underlay could be a concrete slab, a the use of wood vceneer floorboards or wooden sub-floor made of flooring panels similar laid on a rigid substrate. The boards laid on battens or joists etc. The boards are are placed on top of a thin sliding layer, for joined either by gluing in the T&G according exampe a 0.20 mm PE-foil and/or a cork to manufacturer¶s instructions or by the use sheet placed on the rigid underlay. The ri- of purpose-made clips placed in grooves on the backside of the boards, see figures 84-85.

FLOATING FLOORS 55 It is required to supply planks and flooring Laying a floating floor panels with T&G on all four sides in order The laying instructions described below refer to use them as floating floors placed directly to plank floors in the form of floorboards, on top of an intermediate layer. wood veneer floorboards and the like. For Flooring panels used as sub-floors must the laying of parquet blocks, parquet tiles or carry a marking stating approval for use in blocks on a floating sub-floor, reference is floor constructions. made to the subsequent section about glued The floor plane must not be fixed, i.e. and nailed floors. should be able to move freely. It is The first row of boards is laid with the important to observe that there shall be a groove facing the wall. The boards are distance of minimum 10 mm between floor aligned by the use of a building line. A and all surrounding walls and around distance of minimum 10 mm between the penetrating installations, for example pipes. wall and the board must be established. In This distance depends on the size of the rooms exceeding 6 m - measured across the floor and the manufacturer¶s grain direction in the wood - and 12 m along recommendations should always be the grain direction, the distance shall be followed. increased in accordance with room In order to prevent the floor from dimension and wood species. Temporary cracking it is normal procedure to establish distance blocks are placed between the first dilatation joints at every 8 m across the row of boards and the wall in order to width of the floor (measured ensure that the boards are not displaced perpendicularly to grain direction in the during the laying, see figure 86. wood). It is also recommended to establish dilatations joints in floating floors subject to heavy loads, as for example in offices Distance blocks with heavy filing cabinets, because the load may prevent the floor from moving freely. In case dilatations joints are not established the result may be cracks and chinks in the floor. The floor may also crack in case the room is very irregular and in this way hindering the free movement of the floor. Groove T&G floorboards joined with steel clips Tongue Intermediate layer

Figure 86 Laying the first row of boards with the groove facing the wall and held in position by temporary distance blocks. Intermediate layer Moisture barrier Concrete The next row of boards is now placed and the Figure 85 Floating floor carried out with boards are knocked together using a floorboards joined with clips and laid on a rigid underlay, for example concrete. A thin hammering block or a hammering rail. In intermediate layer which may function as a sound some cases the hammering block may simply reducing layer and as a moisture barrier at the consist of a sawn off piece of board, whereas same time is introduced between floor and other products may require the use of a underlay. special hammering block in order to avoid damaging the profile (the tongue side of the board)

56 FLOATING FLOORS The boards are joined by gluing the T&G or The last two boards my be by the use of clips. When joining boards nailed/glued together.², Wedge- end-to-end, the T&G must also be glued. The laying continues using the cut-off from Bevelled edge a previous row as the starting board in the next row. Using this principle, the end-to- end joints of the boards will be staggered. End-to-end joints in two neighbouring rows shall be staggered by minimum 500 mm, see figure 87, The last board is adapted as shown in Figure 89 Laying the last board(s) figure 88. It may be difficult to fit in the last board. The process of fitting the last board can be made easier if the lower side the upper lip of the groove is chamfered.

Hammering rail

Minimum 500 mm

Avoid uniform staggering of the boards

Figure 90 The last board is knocked into place by the use of a hammering rail or squeezed into place by the use of a crowbar. Figure 87 Placing end-to-end joints of the It is also possible to cut the edge of the boards. Avoid closely placed end-to-end joints board at a slight inward angle on the side in neighbouring rows (zig-zag-pattern). facing the wall. In case the last board is very narrow it may be necessary to lay the last two boards simultaneously. In this case they should be glue-joined before laying them, see figures 89-90. In case the supplier recommends that the floor is laid in accordance with the 10-board measurement, it is required to observe the measurement requirement indicated. The 10-board measurement indicates how wide an area 10 boards should cover. The 10- board measurement is indicated as an interval, for example 1293-1298 mm, i.e. the covering width of 10 boards shall fall within this interval. The measurement depends on: The width of the boards, the Figure 88 Tracing the size of the last board. expected highest air humidity and the floor product used.

FLOATING FLOORS 57 Doors with a threshold Doors without a threshold The floorboards extend under the threshold. It is usual practice to establish a joint It is required to establish a distance of between the two floors where they meet in minimum 20-30 mm between the floorboards the door opening in order to allow for where they meet in the door opening ± movements caused by humidity changes. depending on the sizes of the adjoining floors. The joint can be concealed by the use of a In case the boards are perpendicular to the flat or curved metal cover strip fixed in door opening, as shown in figure 91, the one of the floors only, see figure 93. The joints between the boards should be aligned cover strip must not be countersunk into on the two sides of the threshold. The levels the floor as this may prevent the free of the floors in adjoing rooms should be the movement of the floor. same. In case this is not possible, the threshold should be packed to the level of the highest Wooden floor floor, see figure 92. Wooden floor

Wooden floor Cover strip Minimum 20 mm

Intermediate layer ŶFtfstSpter-re Intermediate layer Moisture barrier Moisture barrier Figure 93 It is usual practice to establish a joint Concrete between floor in adjoining rooms, in particular when the floorboards are perpendicular to each Figure 91 Floating floor with boards perpendicular to other or when they are parallel to the door door opening ± doors with a threshold. opening.

Wooden floor

Wooden floor Wooden floorWooden floor Packing

Intermediate layer

Intermediate layer Moisture barrier

Moisture barrier Concrete Concrete Figure 94 Where there is no threshold, the Figure 92 Packing the threshold between floorboards may continue through the door floating floors at different levels. opening. It is, however, recommended to use this method in smaller rooms only.

58 FLOATING FLOORS Where there is no threshold, the Glued or nailed floors floorboards may continue through the door A wide range of wooden floor materials opening, as shown in figure 94. may be laid either as glued floors or as When boards run through the door nailed floors directly on a subfloor. opening, it is required to dimension the joint The subfloor shall be stable and rigid. The along the walls in both rooms as if the floor requirements to evenness and flatness of the were one floor with a total width subfloor are the same as requirements corresponding to the width of both rooms applying to the final floor. Deviations from measured through the door opening. flatness shall be less than ± 2 mm measured with a 2 m straightedge, see Appendix: Pipe penetrations Flatness. All holes for pipes shall have a diameter 20 The subfloor must be without any level mm larger than the pipe going through the differences and there must be no sharp hole in order to allow for movements. points. In case the requirements to flatness Around existing pipes it is possible to cut are not fulfilled, it is required to adjust the out a V-shaped block shown in figure 95. flatness, for example by means of sanding or After placement of the board, the block is by the use of a filler compound. glued back into place and covered with a pipe escutcheon. Nailing/screwing All wooden floors with a tongued and grooved floorboards/blocks may be nailed or V-shaped block screwed to the substrate ± provided the substrate is suitable for such fixing ± for example a new subfloor made of particle board or an existing wooden floor. Nail and screw dimensions must be chosen in accordance with board thickness, see Fasteners and adhesives. In case the subfloor is made of particle board, it is required to use screws. Fixing is normally carried out as secret fixing, i.e. by screwing or nailing at an angle - Concrete starting at the topside of the tongue (see Intermediate layer figures 97-98). The secret fixing of wood veneer floorboards with a core of particle Figure 95 Cutting out for a pipe. The V-shaped block is glued back into place and covered with a board must not be carried out without pipe escutcheon. consulting the manufacturer. On concrete subfloors, the fixing may be carried out by screwing directly into the concrete - see Fasteners and adhesives.

The laying of floorboards ± screwing or nailing. The principles applied are similar to those principles described in the section concerning floors on battens/joists. The first row is laid with the groove facing the wall. The boards are aligned by the use of a building line. A minimum distance of 10 mm must be observed between the board and the wall. In rooms with dimensions exceeding 6 m measured across the boards, and 12 m along the boards, it is required to increase the distance between the boards and the walls in accordance with room size. Temporary distance blocks are placed between the first row of boards and the wall in order to ensure that the boards are not being displaced during the laying of the remaining part of the floor.

GLUED AND NAILED FLOORS 59 Floorboards/screwed from top side Boards fixed with visible nails/screws, should be fixed with a screw/nail placed approximately ¼´board width´ from the grooved edge of the board. Boards which are particularly wide, i.e. 200 mm or more, are fixed with two visible nais/screws in Wood floor every board, see figure 96. It is possible to close the nail/screw holes using wooden plugs.

Tongue Distance blocks

Figure 97 Fixing of the first board and secret Groove nailing of the remaining boards. Min. 10 mm

Intermediate layer Wood panel subfloor T G

Figure 96 Floorboards nailed or screwed from the top side. In case the boards are more than 200 mm wide, they must be fixed with two screws Figure 98 Dimensions and placement of observing the distances indicated. screws using secret fixing, for example on concrete Floorboards secret nailing/screwing The first board is nailed from the top and also secretly in the tongue, see figure 97. The visible nail in the first board is placed some 20 mm from the grooved edge of the board. Brads are countersunk with a nail puncher, and holes are filled using an appropriate filler. The tongue side of the board is nailed through the upper side of the tongue. Nails are placed at an angle between 45° and 60° in relation to the upper side of the board. Nails are punched. Hammering block In some cases it may be advisable to pre- bore in order to avoid the splitting of the wood. A similar fixing may be carried out Figure 99 Boards are knocked together using a using screws ± also when fixing to hammering block or a hammering rail. concrete, see figure 98. When nailing, it is important to blunt the point of the nail in order to avoid splitting of the wood. The head of the nail may be used for punching the previous nail. In this way the head will be slightly flattened - obtaining an oblong shape narrow in one direction.

60 GLUED AND NAILED FLOORS When nailing, the narrow edge of the nail head should be kept parallel to the wood grains. This will reduce the risk of splitting the wood. Nail dimension guidelines are shown in table 2 on page 17. Nails should be placed at least at every 600 mm, but nails should never be placed closer than 50 mm from the Minimum 500 mm end of the board, see figure 96. Subsequent rows of boards should now be Avoid placing end laid, and the boards are knocked together. joints in neighbouring The hammering block could be made of an rows too close off-cut from one of the floorboards. In some cases it is required to use a special hammering block in order to avoid damaging Figure 100 The placing of end joints. Avoid the the board profile (the tongue), see figure 99. too close placement of end joints in neighbouring End joints of boards shall be glued in the rows (zig-zag-pattern). T&G, but must never be glued in the T&G along the sides of boards. The laying is continued in subsequent rows ± always Wedge The last two boards may starting a new row with the piece of board be glued/nailed together. Chamfered edge left over from the previous row. Doing so, limes/s0mmes sammen the end joints between boards will automatically be staggered. End joints in two neighbouring rows should have a distance of minimum 500 mm, see figure 100. It may be difficult to fit in the last board, but the process can be made easier by Figure 101 Laying the last board chamfering the upper lip of the groove on the last board. The board may also be cut at an angle on the side facing the wall. In case the last board is very narrow it may be required to fix the last two boards at the same time. In this case they are glued together before laying. See figures 101- 102. In case the supplier recommends laying the floor in accordance with the 10-board measurement, the covering width of 10 Hammering rail boards must be stated. The 10 board measurement is indicated as an interval, for example 1293-1298 mm, indicating the tolerance of a random measurement across any 10 boards in the floor. The measurement depends on the width of the Figure 102 The last board is knocked into place boards, the expected variation in air by the use of a hammering rail o it may be pressed humidity during use and the wood species into place using a crow bar. used.

GLUED AND NAILED FLOORS 61 Gluing Distance blocks When gluing it is important that surfaces are clean, dry and ready to accept glue, see Fasteners and adhesives. Minimum 10 mm Flooring materials must not be twisted and shall have a perfectly plane underside ensuring good bonding. Parquet blocks without T&G shall have a maximum length of 300 mm. Parquet Minimum 80 mm Groove blocks with T&G shall have a maximum length of 700 mm. Solid wooden floorboards cannot normally be glued to the substrate as it may be GlueLim difficult to ensure sufficient bonding throughout the length of the board and also Concrete Tongue Groove because the moisture related movements in the boards are greater than the elasticity of Figure 103 Laying the first parquet blocks with the the glue. grooved edge facing the wall and fixed in place by Wood veneer floorboards should only be the use of distance blocks. It is required to choose glued to the substrate in case the blocks of such length that end joints in neighbouring rows are always staggered minimum manufacturer recommends so - and provides 80 mm. laying instructions for this method. It must be ensured that the glue has filling capacity and the the substrate is plane, (i.e. Wooden maximum +/- 2 mm deviation measured floor along a 2 m straightedge and +/- 0.6 mm when measured along a 0.25 straightedge) in order to secure good contact between glue and boards throughout the glued surface. Glue The laying procedure is similar to procedure for nailed floors. Concrete The first row is placed with the groove- side facing the wall. The blocks are aligned by the use of a building line. Minimum 10 mm distance between floor and wall must be Figure 104 Wooden floor, for example parquet observed. blocks glued directly on top of concrete or on a In rooms larger than 6 m measured across screed. It must be ensured that the concrete slab is wood grains and 12 m measured along the adequately level and dry. grains, the distance to surrounding walls, or any other surface bordering the floor, must be increased ± depending on room dimensions. Use a sufficient number of wedges to maintain the gap at a suitable size and to press the boards together, see figure 103. In case gluing takes place directly on top of a concrete slab or a cement mortar screed, it must be assured that the remaining moisture is less than 65 % RM, when measured in the temperature interval 17-25°C, see figure 104. In case there is a need to glue a floor with a higher moisture content in the concrete, it is required to insert an effective moisture barrier, for example bitumen felt, between the subfloor and the wooden floor, see figure 105.

62 GLUED AND NAILED FLOORS Bitumen felt may be glued to the substrate Wooden floor using acryl dispersion glue, for example parquet glue or glue suitable for gluing PVC-coverings, provided the residual moisture content is below 85 % RH. The Glue requirements concerning quality of the bitumen felt to be used are described in the section regarding Subfloors, bitumen felt (page 13). Glue In case there is a need for a softer floor or for impact sound reduction it is required to insert an intermediate layer, for example Concrete Bitumen felt rubber cork. The intermediate layer is glued to the concrete floor, and the wooden Figure 105 Wooden floor, for example parquet floor is glued to the intermediate layer once blocks, glued on top of an effective moisture the glue below the intermediate layer is dry barrier such as bitumen felt (in case the concrete see figure 106. is too moist gluing the parquet blocks directly on The underlay must be as uniform and level top). The moisture barrier may be glued to the as possible in order to ensure the best concrete slab provided the residual moisture possible adherence. To achieve this it may content is below 85 % RH. be necessary to level the entire floor using a levelling compound. Porous and very absorbent floors such as concrete, light weight concrete, anhydrite, gypsum etc. should always be primed before gluing. In the case of anhydrite it is required to use a special primer, which, apart from securing adherance, also prevents the moisture in the glue from damaging the substrate. The flooring materials are glued all over the surface using a´ filling glue´ in Wooden floor accordance with the recommendations issued by the floor supplier. It is advisable to plan the laying of the Glue floor in such a way that walking on already laid areas is prevented. It is recommended only to apply glue to such an area that can Concrete Glue easily be laid withih 15 minutes. The size of Impact sound insulation such an area will depend on the moisture and temperature conditions in the room as well as the nature of the material used as Figure 106 Wooden floor, for example parquet subfloor. blocks, glued onto a layer insulating against It is advisable to load the floor, for impact sound, which again is glued to the concrete example using sand bags, until the glue has subfloor. hardened. This is particularly important along floor edges. Walking on newly glued floors should be strictly avoided until the glue has hardened. The hardening process normally takes minimum 24 hours. The wooden floor must not be sanded or surface treated until the parquet blocks are in complete moisture balance with the moisture conditions in the room. This may take up to 7 days.

GLUED AND NAILED FLOORS 63 The laying of parquet floors using single blocks. Parquet floors laid as single blocks may be laid in a variety of patterns, for example herringbone, Dutch pattern or braided pattern. Creating patterens is more complicated than most other processes in floor laying. Starting a pattern requires meticulous skills and planning, because the correct laying of these first blocks determines the quality of the final result, see figures 107-110. Special blocks for the laying on the left hand side and on the right hand side are available for patterned floors. Also special Glue elements such as squares and narrow beads in contrasting woods area available. When laying more complicated patterns it is required to cut pieces to size in situ, which again requires excellent Figure 108 Apply glue corresponding to the width of one row of blocks at a time. Set the blocks in craftsmanship and special tools. More the glue as close to a neighbouring block as detailed information concerning the laying possible and press the block against neighbouring of different patterns may be obtained from blocks avoiding glue from being pressed up in the the parquet floor supplier. joint betwqeen the blocks. The parquet floor must be sanded after the laying, see figure 11. The extent of sanding required depends on the quality of the blocks and should be discussed with the supplier when choosing type of floor. .

ŶPlywood template Ruler Setting out line Setting out line

Glue

Working line Centre line (of room)

Figure 107 The laying of single blocks in herringbone pattern. Set out the centre line of the Figure 109 Laying the last blocks along room and offset a working line to the right at a the wall. distance corresponding to 1/3 of the width of a block. Set out steering lines perpendicular to the working line using a big try square. Using a plywood template will make it easier to place the blocks perpendicular to each other

64 GLUED AND NAILED FLOORS Laying mosaic parquet or parquet panels. Mosaic parquet floors are most attractive when the pattern is placed symmetrically on the floor. It is therefore required to measure the floor before laying in order to determine the number of ³full panes´ in either direction. The remaining space is divided into 2 equal parts and indicates the dimension of the adjusted panels along the walls. In case the size of the adjusted panels turns out to be less than half a panel it is required to add half a panel in order to maintain the pattern see figures 112-114. The below mentioned procedure may be followed when laying the floor: The position of the corner of the first panel (in the center of the floor) is determined. From Figure 110 Place sand bags on the blocks in this point set out (and fix) two order to establish sufficient pressure until the straightedges perpendicular to each other glue has hardened ± particularly along edges. and parallel to the walls. The first panel is placed and subsequently a row of panels is placed along each straightedge The last panel in each row is adjusted to size and fixed. The panels are turned in such a way that the direction of the fibres changes from panel to panel. The panels are knocked lightly together using a hammering block, carefully avoiding the displacement of already laid panels. Laying the remaining panels takes place diagonally across the floor.

Lim

Figure 111 The wooden floor is sanded and Figure 112 Only apply glue to an area surface treated once the glue is completely corresponding to the number of panels that can hardened and once the floor is in complete moisture be laid within 15 minutes. Start laying the panels balance with the surrounding environment. in the center of the room, alteranting between the the four fields and moving towards the walls.

GLUED AND NAILED FLOORS 65 Centre line Centre line

Big try square

Adjustment along the wall

Figure 113 Laying parquet panels and mosaic Doors with a threshold parquet. Mosaic parquet where the blocks are butt The floor extends under the threshold. It is glued (glued edge to edge) should be broken along required to establish a distance of minimum joints passing through the panel (before laying) in 20-30 mm between the parquet blocks such a way that the four squares are only joined by where they meet in the door opening ± the fabric/mesh on the back side. Set out two depending on the sizes of the adjoining perpendicular centre lines in the room and lay out a number of panels starting from the centre of the floors. In case the blocks are perpendicular room and moving towards the walls. Adjust the last to the door opening, as shown in figure 115, panel at the wall. the joints between the blocks should be aligned on the two sides of the threshold.

Wooden floor

Glue Concrete

Figure 115 Glued floor with blocks Figure 114 Place sand bags on the panels in order perpendicular to door opening ± doors with a to establish sufficient pressure until the glue has threshold. hardened ± particularly along edges.

66 GLUED AND NAILED FLOORS The levels of the floors in adjoing rooms The joint can be concealed by the use of a should be the same. In case this is not flat or curved metal cover strip fixed in one possible, the threshold should be packed to of the floors only, see figure 117. The the level of the highest floor, see figure cover strip must not be countersunk into 116. the floor as this may prevent the free movement of the floor. Doors without a threeshold Where there is no threshold, the flooring It is usual practice to establish a joint may continue through the door opening between the two floors where they meet in between two smaller rooms. However, it is the door opening in order to allow for required to dimension the joint along the movements caused by humidity changes. walls in both rooms as if the floor were one floor with a total width corresponding to the width of both rooms measured through the door opening. Wooden floor / Pipe penetrations Packing All holes for pipes shall have a diameter 20 mm larger than the pipe going through the hole in order to allow for movements. Around existing pipes it is possible to cut out a V-shaped block shown in figure 95. Glue After placement of the board, the block is glued back into place and covered with a pipe escutcheon. Concrete

Figure 116 Packing the threshold between floating floors at different levels.

Wooden floor Glue

Cover strip Wooden floor

Figure 118 Cutting out for pipes in glued floors.

Glue Concrete

Figure 1 1 7 It is usual practice to establish a joint between floors in adjoining rooms, in particular when the floors are perpendicular to each other or when they are parallel to the door opening.

GLUED AND NAILED FLOORS 67 Laying of end grain wood blocks - gluing Ideally, end grain wood blocks should be placed on top of a wood panel subfloor with a thickness corresponding to the thickness of the end blocks. The blocks are laid with joints running along the long side, see figures 119-121. Cross joints should be bond laid, see figures 119-120. A distance of minimum 20 mm must be observed along walls, pipes etc. In order to allow for free floor movement and expansion, see figures 121-122. The best result is normally achieved by placing thoroughgoing joints parallel to the shortest walls of the room. Before laying the floor, it is advisble to consult the floor supplier concerning choice of glue tye. The blocks are glued throughout the surface, see figures 121-122. They are Figure 119 Place the blocks correctly and in placed side by side in the glue and must not bond ± sapwood against sapwood ± heartwood be pushed together as such movement may against heartwood. cause the glue to be pressed up into the joints, and this may consequently lead to priming (which is an exacting procedure). . cracks in the joints (or worse in the block The concrete must be dry before laying with itself) caused by moisture movements in the a relative moisture content less the 65%. floor since the individual movement of the This requirement also applies to screeds and each block is being restricted. filler compounds which must also possess sufficient strength. Laying end grain wood blocks on concrete Some suppliers of end grain wood blocks do not recommend glue fixing due to the risk of adherence failure caused by lack of concrete

Centre line

Try square Steering line

Wood panel subfloor

Figure 120 Laying end grain wood blocks. Set out centre line of the room and a number of steering lines perpendicular to the centre line. Start laying blocks (in bond) from the centre line towards the walls.

68 GLUED AND NAILED FLOORS When applying porous self levelling compounds, for example anhydrite, it is important that the concrete surface is clean of cement slurry and thoroughly primed. Whenever there is a risk of capillary End grain wood blocks moisture rise, it is required to lay out a moisture barrier. When using liquid moisture barriers such as epoxy based barriers it is important to observe the recommended thickness in order to ensure an effective barrier function. Moisture barrier Before laying it is recommended to consult the floor supplier concerning choice Glue of primer, moisture barrier and glue type. Wood panel Concrete and screeds should be primed Intermediate layer and a levelling compound should be Figure 121 The blocks are placed in the glue close applied, for example a self levelling to neighbouring blocks and pressed into the glue compound in order to establish a plane avoiding glue from being pressed upwards into the surface without voids or irregularities (+/- 2 joints. mm when compared to a 2 m straightedge). Once the floor is dry the surface is sanded Blocks with disk floor sander until the surface is clean and free of burrs and slurry. Subsequently the surface is primed, for example using parquet glue (diluted to 1:2 strength). Once the primer is dry, the blocks are laid as described above

Surface treatment Sanding of the surface may be carried out Glue minimum two days after lying. Sanding dust is completely removed and the floor is treated, for example with floor oil, according to manufacturer¶s instructions. Wood panel The laying end grain wood blocks in sand. Intermediate layer End grain wood blocks may also be laid in layer of sand - 20-30 mm in thickness and (Moisture barrier) levelled out. Joints are filled with sand. When applying this method, the risk of Figure 122 Cutting out for pipes in end grain wood block floor. block displacement caused by mechanical action and moisture movements is bigger compared to the glued floor. However, it is easier to make changes and repairs in this type of floor and the blocks may be reused. The blocks should have a thickness of minimum 80 mm. A distance requirement of minimum 20 mm should be observed along walls and pipes etc. The quality of the sand to be used is described in the section Sand, see page 16. The floor should only be cleaned by sweeping.

GLUED AND NAILED FLOORS 69 RENOVATION

When renovating a floor, similar requirements as those applying to new New wooden floor floors are to be observed. The floor must have sufficient strength and stiffness and it Intermediate layer must be firm, dry and plane in order to provide satisfactory conditions. Old floor coverings, such as linoleum and carpets should be removed ± which is also Existing preferable from indoor climate and construction hygienic points of view. In case an existing wooden floor is to serve as a subfloor for a Figure 123 The laying of a new floor on top of new floor, it may be required to re-nail the existing old floor. floor in order to ensure firmness. In case it is required to lay floorboards on top of existing substrates it may be necessary to level out such substrates in order to meet agreed requirements concerning planeness Impact sound and levelness. It is normally required that insulation floors are level and that deviations from planeness fall within ± 2 mm when New floor compared to a 2m straightedge and ± 0,6 mm when compared to 250 mm straightedge. When carrying out renovation work it may be very difficult and costly to meet one or both of these requirements as a result of building settlement or deformations Existing or sagging joist. It is therefore required to construction agree on the accepted tolerances concerning planeness and levelness before renovation Figure 124 Laying a new wooden floor with an impact sound insulating layer on top of existing work takes place. floor. The threshold may be lifted up by pugging. Levelling may be carried out using levelling compounds or, in the case of floorboards, by applying a layer of (10-14 mm) may in some cases cause masonite or particle board. uneven elasticity of the floor. This is caused When levelling existing floor joists it is by the fact that the carrying capacity of the required to apply minimum 45 mm thick subfloor may vary in different parts of the boards on top of or along the sides of floor and also that the joints between the existing joists, thereby establishing sufficient thin boards provide limited stiffness across substrate for nails or screws, see figure 126. the floor. New floorboards nailed on top of old Concrete subfloors must be dry. In floorboards should be laid in the same case the pore moisture content exceeds direction as the old ones. Nailing should approximately 65 % in old ground take place only in joists or floor batten and supported floors or concrete crawl space not in the old boards only. decks or basement floors it should be Floating wooden floors may be laid across investigated whether moisture is rising from existing existing floorboards, see figures below, for example capillary rise of ground 123-125. Very thin wooden floors moisture caused by the lack of a moisture barrier.

70 RENOVATION The laying of diffusion tight or moisture Sanding sensitive materials in constructions where Old wooden floors are often renovated by moisture may rise from below may result in sanding and thus removing a scruffy and damages, for example adherence failure or discoloured floor surface, for example old deformation of the wooden floor materials. floor varnish. See also WOOD 47, wooden Before laying a new wooden floor it is floors 2. important to secure the construction with a Initial sanding is carried out diagonally moisture barrier as described in the section using course sandpaper. Once the floor moisture protection - requirements, see appears level it is sanded with finer pages 26-29. sandpaper along the boards. Vacuum cleaning is important between each sanding. The final sanding is carried out using fine sandpaper. Hard wood In corners, along skirting boards and cladding under radiators where access with the floor sanding machine is impossible, it is required to use a special floor edge sander New wooden floor with a rotating round sanding disc. Places Impact inaccessible to the edge sander are cleaned sound with a wood scraper and sanded with a delta insulation sander. Before sanding old floors with a thick layer of varnish it is advisable to apply a Existing thin layer of special sanding oil in order to construction prevent the varnish from sticking to the sandpaper during sanding. Figure 125 Laying a new wooden floor on top of existing floor ± using impact sound Joints insulation. The threshold is clad with hardwood Renovating old wooden floors by caulking existing joints with a caulking compound requires careful assessment and planning. It New members tacked on is necessary to thoroughly clean the joint side of joists and this is best done using a plunge router. In case the floor is oil or lye treated it is recommended to carry out a test joint before caulking the entire floor. The caulked joint is assessed with regards to adherence and compatibility, typically after curing for 8 days. It is recommended to consult caulking compound supplier concerning the applicability of the chosen solution. Existing construction Damages in caulked joints Damages in caulked floor joints may be caused by adherence failure as a Figure 126 Straightening existing joists by tacking consequence of non compatibility of new members on the side(s) of the joists. By caulking compound and wood specie or tacking members on either side of the joist it is possible to reduce the distance between supports. caused by movements larger than the caulked joint is able to accept. Such joints must be replaced by cutting out, cleaning, priming and re-caulking. Notice that renovated joints may not achieve the same appearance as new joints. When replacing caulking compound it may be required to re-sand the floor.

RENOVATION 71 DAMAGES AND REPAIRS Floorboard where the lower lip of the groove has been removed Partial repairs Limited damages, for example in a single floorboard or in a single parquet block may be repaired using partial repair or substitution. Glue Floorboards on floor battens or joists Ply wood gusset plate Boards laying on joists or on floor battens are ripped twice along the board and cross Figure 127 Replacing a damaged floorboard placed on floor batten or joists. A plywood gusset plate is cut in two places ± all cuts are placed 20 mm inserted between battens/joists and the new board is from the edges. A hand held circular saw glue fixed to the plate. with adjustable cutting depth is used. The depth is set according to the board thickness. Glued floors After cutting, the centre piece may be Glued floors consisting of blocks without removed, but it may be required to use a T&G may be repaired using a new block chisel in order to cut it loose because of the which may be laid and glued directly. circular cut at the ends. Hereafter all the In case the blocks have T&G it is remaining parts of the board may be required to remove the tongue at one end of removed - using the chisel, and possible glue the block and the lower lip of the groove. remains are removed from tongue and The block is placed by inserting the tongue groove of the neighbouring boards. A new into the groove along the neighbouring board of the same material is cut to size and block, see figure 128. The glue joint must be the lower lip of the groove is removed. A 12 loaded until the glue has hardened. Hereafter x 80 mm plywood gusset plate (or similar) is the block is sanded until it becomes level glued to the underside of the remaining with the neighbouring blocks. board, serving as support for the new board. In the case of wood veneer floorboards it The gusset plate is clamped against the is possible to obtain repair blocks allowing board until the glue has hardened. for substitution of single blocks in the Subsequently, glue is applied to the gusset topmost layer, but in most cases it is plate and to the tongue and groove of the preferable to substitute the entire board. boards, whereafter the board is tilted into position, see figure 127. When boards have T&G on all four sides, it is required to cut off the tongue in the end of the board. When using unsupported butt joints it is required to support both ends of the board using the above described plywood glued to the underside of the Parquet block Glue neighbouring boards. It is required to add where the lower lip load to the board until the glue has of the groove has hardened. Hereafter the board is sanded been removed until it becomes level with the neighbouring boards. When single parquet blocks are Figure 128 Substituting a damaged parquet block damaged it is possible to remove the centre glued to the substrate. Load must be applied on the part by use of a plunge router. Moulding is block until the glue has hardened. carried out minimum 8 mm away from block edges. The remaining part of the block may be removed using a chisel.

72 DAMAGES Squeaking Squeaking may also be caused by failure in Most problems related to squeaking floors the subfloor, either caused by the are caused by use of wood (for joists and displacement of some of the packing pieces, floor batten) which was not sufficiently dry or because the battens/joists have not been when the floor was laid. It is therefore properly levelled out. After some time a possible ± to a large extent ± to solve most small space may occur between the boards such problems, simply by using dry and the battens/joist which have sagged. construction timber. Squeaking may occur This causes movement of the boards in when the wood dries out and shrinks, and relation to the nails and squeaking occurs thereby creates a cavity between batten/joist and the floor seems to give way. and a floorboard. The squeaky sound is So far no safe methods may be prescribed created when the floorboards, as a in order to repair failure in battens/joists. consequence of traffic, are moving up and In some cases an acceptable solution may down - grinding against the nails. be achieved by pulling the batten and the The squeaking may be removed by board together using screws from above. pressing the boards against the batten/joist Special screws, with a course self tapping and thereafter re-nailing or screw fixing thread, have been developed with the them. As a first measure it may be sufficient specific purpose of repairing batten to hammer the existing nails deeper into the constructions where the packing has failed. construction by placing a large wooden The screw is driven through the batten block on top of the floor and hammer on in whereby it cuts a thread. By adjusting the with a big hammer. screw it is possible to lift or to lower the Squeaking may also be caused by the fact batten and thereby substituting the packing that the floor has been nailed with a nailing locally, see figure 129. gun, using secret nailing and for example When using special screws, care must be wire nails. If the floorboards have not been taken not to damage pipes and cables which pressed sufficiently tight against the may run under the floor. B batten/joist, the boards will rest on the wire In case of extensive damages, the only nails. This will cause squeaking between repair method recommended is re-laying the board and batten/joist, because the boards entire floor. are not properly fixed. Squeaking also occurs when wood veneer Wooden floor - Wooden plug floorboards, with a core made of particle board, are fixed using secret nailing, because the nails do not get a proper grip in the soft core. In this case the only way to remove squeaking is re-nailing from the topside. When re-nailing old floorboards from above it is recommended to use ringed and Floor batten twisted flooring nails, for example 3.5 x 55 mm for boards 20-22 mm in thickness, and 3.8 x 65 mm for boards 25-28 mm in thickness. Re-nailing should only be carried out at such a time when it is absolutely -Floor-Jack screw certain that the battens/joists are in moisture equilibrium with the surrounding air. When re-nailing a floor where secret nailing has been used in the first place, it is most often possible to detect the placement of battens/joists by knocking on the floor or by Figure 129 Floor-Jack screw may be used in case the use of a metal detector. the packing fails locally. Do not tighten the screw excessively as this may cause the lifting of the floor.

DAMAGES 73 In case the forces become excessive the floor will either bulge, which normally happens to floating floors, or in severe cases, it may push out the walls. When a wooden pine floor with 10 % moisture content just touches the surrounding walls, the pressure it may exercise when moisturized during use may reach approximately 2.5 N/mm2 radially and approximately 1.5 N/mm2 tangentially. 2 Figure 130 Cupping of boards ± wash board ± Assuming an average of 2 N/mm , a 22 mm most often caused by moisture on the underside of board may exercise a pressure corresponding the boards. . to 2 x 22 x 1000 N/lnm, equalling approximately 4.4 tonnes per meter!!! Curved boards Repairing damages caused by moisture In case the floor is laid on a moist substrate expansion is done by cutting along such the backside will absorb the moisture and edges that are prevented from free expand. This may cause lasting deformations movement. The aesthetic damages, in terms in the form of curved boards, often referred of cracks, are difficult to repair with a good to as wash board, see figure 130. Wash result. In case of minor damages it may be board may be prevented by ensuring a dry sufficient to re-sand the floor; otherwise it substrate or by the use of a moisture barrier. may be necessary to re-lay the entire floor. In case the deformation is caused by construction moisture it may be possible to Cracks alleviate the problem by sanding the floor, When drying out the floor will shrink and once the building has reached moisture natural joints will occur between the boards equilibrium. or blocks. In cases where the moisture In case the problem is caused by rising determined shrinkage is hindered, it may ground moisture it is most likely cause excessive partial cracks, because the necessary to insert a moisture barrier. In this tensions which are built up in the wood will case it is required to re-lay the floor. be released in the weakest ponts. In many Wash board may also occur when laying cases the shrinkage will be concentrated in floorboards with a moisture content of 12- single joints or in single boards. The cracks 17 %. When the floor dries out to 6-8 % occurring in such instances will have a moisture content, the boards will dry out on width corresponding to the total shrinkage the top side first, thereby causing them to of the floor. This is a widely known curve. problem in floating floors which, in many cases, are being fixed in position by heavy Pressure shrinkage and expansion loads from furniture and equipment or pressure columns and hard and strongly adhesive In case a wooden floor is moisturized after caulking compounds in joints (which in laying, it may expand considerably and this many cases are carried out without the use may cause problems. In case the boards are of backstopping at the bottom of the joint). being prevented from moving, for example Alleviating such problems may be done by when they meet a column or a wall, the cells inserting a dilatation joint in the crack. In in the wood will be pressed together, and the case the dilatation joints are planned before boards will appear visibly narrower after the floor is laid, it is possible to control in drying out again. This phenomenon is known which areas the floor must be able to move as pressure shrinkage. freely, and also how wide the dilatation joints should be.

74 DAMAGES APPENDIX

Moisture measuring In order to assess moisture conditions, for example construction moisture, before laying a wooden floor or in order to determine causes of damage, it is necessary to be able to measure moisture. Moisture measuring in relation to wooden floors includes measuring of relative air humidity, measuring moisture in subfloors, particularly in concrete in light weight concrete and measuring of moisture in wood materials. Below, a number of the commonly used methods are described briefly. A more extensive description of Figure 131 Moisture meter ± Capacitive moisture the methods may be found in SBI- meter ± suitable for detecting differences in Directive 170: Measuring methods used in moisture content. building analyses; GSO ³Floor facts´(Gulvfakta) and various standards. Capacitive moisture meters are not suitable When measuring moisture, special attention for the testing of absolute moisture content should be given to the following aspects: expressed in %. However, they are well suited for finding differences in moisture ‡ The user must be confident with the content, for example for the spotting out of equipment used and must be able to particularly dry or particularly wet areas of assess the results. a floor. The meter is non-destructive as it ‡ Apart from the ability to use ordinary measures on the surface with a measuring moisture check methods, it is also a dept of up to 35 mm. precondition that the user possesses The Appendix: Moisture measuring in knowledge about building physics in order concrete gives a more comprehensive to be able to assess the results. explanation of the steps to be followed ‡ Moisture conditions in a construction when detecting wet and dry areas of may vary considerably from one area to concrete subfloors. Reference is also made another. Consequently, it may be to GSO Floor fact (Gulvfakta). necessary to carry out several tests in order to get a correct image of the Measuring of moisture in concrete and conditions. light weight concrete ± relative moisture in ‡ The tests should be carried out over a a drilled test hole. sufficiently long period in order to make The most commonly applied method for sure that moisture conditions are in measuring moisture in concrete is to equilibrium. measure the air humidity in a drilled hole in ‡ Moisture conditions may vary the concrete. Normally, a hole with a considerably throughout the year, and depth corresponding to 0.4 x the thickness assessment of results must consider this of the concrete slab is drilled. After vacuum fact. cleaning the hole, a probe is inserted into the hole and the hole is sealed off in order Measuring moisture variations in to allow the establishment equilibrium substrates ± capacitive moisture meter between probe and the relative air humidity The measuring instrument, which is cheap in the hole. It normally takes from several and easy to use, is placed directly on top of hours up to several days until equilibrium is the surface of the material to be tested, see achieved, see figures 132 and 136. figure 131. When measuring, the result is shown as a value depending on the moisture content.

MEASURING MOISTURE 75 wet and the dry thermometer is an expression of the relative air humidity. The method is relatively accurate and is often used for calibrating other meter types, for example the thermo hygrograph.

Measuring temperature and relative air humidity using a thermo hygrograph. A thermo-hygrograph consists of a bimetal thermometer and a hygrometer shaped as a hair harp. Both parts are connected to a pen which records the measured values on a rotating drum supplied with a sheet of recording paper. The drum makes one full turn over a certain period of time ± normally one week. The result is a complete record of temperature and moisture variance during the period. As is the case with all types of hygrometers, it is required to regenerate and calibrate the hair harp at relatively short Figure 132 Electronic moisture meter for the intervals in order to get reliable results, cf. measuring of relative air humidity and relative air SBI-Direction 170. humidity in a drilled hole in concrete or in light weight concrete. Measuring temperature and relative air moisture using a data-logger Data-loggers are comparatively new As an alternative it is possible to take out devices used for the measuring of samples which are subsequently placed in temperature and relative air humidity, see plastic containers with a tight fitting lid, and figure 133. They are operated via a PC and the testing is carried out inside the container. The taking out of samples must be done manually, for example by chiselling, as water or heating from a water- cooled drilling machine may distort the test material.

Measuring relative moisture content using a psychrometer. When using a psychrometer it is possible to make an instant measuring of moisture content. A psychrometer consists of two precision thermometers of which one is covered with moistened muslin wick. The air passes by both thermometers and evaporation takes place around the moistened muslin wick ± causing cooling. The difference in temperature between the Figure 133 Data logger for the measuring of temperature and relative air humidity.

76 MEASURING MOISTURE may be programmed for measuring during varying time intervals, from a few minutes up to several months. Measuring and data collection take place by means of a small electronic device, and does not require linking up with cables during measuring. After measuring, all data are transferred to a PC for further processing.

Testing moisture content in wood using an electric resistance meter (pin type meter) The most commonly used instrument for moisture measuring in wood on the building site is a moisture meter based on the measuring of electric resistance between two electrodes knocked or pierced into the wood, see figure 134. The method is based on the fact that the electric Figure 134 Electric resistance meter for the resistance between the electrodes depends measuring of moisture content in wood. on the moisture content in the wood. The market offers a variety of brands, but in principle only two different types. One type is supplied with insulated electrodes, which only allows for measuring at the tip of the electrode. This may be an advantage since the method prevents disturbances in the test result, for example caused by condensed water on the surface. The other type is supplied without this insulation and is often cheaper and easier to work with. Measuring takes place along the grains and never across cracks or knots or close to nails or screws. It is required to measure at a distance of minimum 300 mm from end wood and as a minimum measuring should take place in three different places, see figure 135. The moisture content in floorboards should be measured at both ends of the board as the density at top end and root end varies. As a result the moisture content and Figure 135 Measuring takes place along the grains the drying out time differ in the two ends. and at a distance of minimum 300 mm from ends. Most instruments indicate the moisture content directly in %. The instruments are normally calibrated for the measuring of pine and spruce and it is required to adjust test results when measuring in other materials and species. Likewise, it is required to adjust results when the temperature deviates considerably from 20°C. Liquids used for pressure impregnation may change the conductivity of the wood causing results to be unreliable in pressure impregnated wood.

MEASURING MOISTURE 77 Measuring moisture in concrete Before laying wooden floors on concrete or light weight concrete substrates it is required Moisture meter to ensure that the moisture content in the subfloor does not harm the wooden floor materials. The procedure used when testing moisture content in concrete is briefly described below. A more thorough description of methods may be found in GSO´Floor facts´ (Gulv-fakta). Drilled hole

Procedure The floor is subdivided by means of a modular grid in such a way that each field Seal 0.4xconcrete covers approximately 10 m2. Initial testing is thickness (B) carried out using non-destructive testing equipment, for example a capacitive moisture meter at every modular grid intersection point, in order to determine ³most wet´ and Tight covering ³most dry´ areas. Subsequent measuring is carried out using equipment for the measuring Drilled hole Drilled hole- of relative moisture in a number of drilled holes, see figure 136. Measuring is carried out in ³most wet´ and in ³most dry´ areas as well as in normal areas. Normal areas are defined as such areas having a moisture content averaging %RM % RM the two extremes. The number of tests depends on floor size, see table 6 Figure 136 Measuring moisture in concrete by measuring the relative air moisture inside drilled Table 6 Number of moisture test per floor holes. Notice that the moisture content in the concrete substrate is levelled out by the application Floor Number of non- Number of of a diffusion tight cover, for example bitumen felt. size in destructive relative moisture At the bottom of the hole (approximately 0.4 x m2 tests content tests concrete thickness) the moisture content is more or up to100 14 2 less unchanged. up to200 27 4 up to 400 54 5 up to 600 80 6 In case wooden floors are laid directly above 600 14 per. m2 1 per 100 m2 on top of concrete it is required that the moisture content in the concrete is less than 65 % relative moisture content. Notice that the measuring of relative moisture When bitumen felt is used a moisture content inside in a drilled hole should take barrier below the wooden floor, the place over considerable time in order to moisture content in the concrete shall be establish equilibrium between moisture in the less than 85 % relative moisture content in concrete and the relative air moisture inside order to allow for the glue to harden. the hole, see Appendix: Moisture measuring, page 75, concerning the testing of moisture in concrete and in light weight concrete.

78 MEASURING MOISTURE Acceptance check EDG-Recommendation issued 22nd When wooden materials are received at a October 1994 specifies three moisture building site it is recommended to carry out classes for wood and wood based material: an acceptance check including such aspects Standard (S), Quality (Q) and Exclusive as visible mechanical defects, number of (E). Each class defines tolerances as to the pieces, dimensions, wood quality etc accepted deviations from desired moisture In the case of wooden materials such as content (measured value). For class boards and floor battens it is also Standard the accepted deviations are ± 0.3 x recommended to assess wood moisture measured value, and for Quality the content as this is a hidden quality. Standards accepted deviations are ± 0.2 x measured should be defined for moisture content, for value. example 12 % average moisture content, As for kiln dried boards it may be which is a realistic demand in the example of desirable to accept a symmetrical interval floor battens. In case the wood moisture around the desired value, like for example content does not correspond to the set 8% ± 2 %, With respect to floor battens standard, problems may arise later. and joist, normally only the upper values are The moisture content is controlled by of interest. Thus, the requirement may taking out samples. It is advisable to define that a maximum of 5 % of measured determine how samples should be taken values exceed a defined upper limit. For beforehand, i.e. how many samples should samples with a very limited number of be taken, how they are measured and how results one may, as an alternative, define test results are handled/assessed. requirements such as: number of samples, The number of samples included in the maximum average moisture content, utarg, acceptance check depends on the total and number of results accepted to exceed utarg number of boards, battens or blocks with + 2 or +3 %. included in the acceptance check and the chosen quality class. Example 1: Table 7 lists up some proposals Ten samples with an average moisture content of concerning the number of samples 12 % are required. Further, only one out of ten results is accepted to equal or be higher than 14 %. necessary in connection with minor jobs In case one result is higher than or equals 14 %, it is required to make ten new tests and none of Table 7 Proposed number of samples to be these results must be higher than or equal 14 %. taken in connection with minor jobs. Concluding: the ten results must have an average Number Number of moisture content of 12 % and at the same time fulfil m2 in job samples the requirement of being less than 14 %. Kiln dried Air dried items boards/blocks 2-8 2 2 In connection with larger jobs it is important 9-15 3 3 to be able to get a clear picture of the test 16-25 4 4 results, the deviations and the unequal 26-50 5 5 distribution of values which is bound to 51-90 8 9 exist in a batch of kiln dried wood. 91-150 1 13 This applies particularly to wood materials 151-280 18 20 from a sawmill whereas such materials like 281-500 27 32 parquets blocks and panelled wood often 501-999 3 45 have a very constant average moisture above 1000 6 60 content with very little deviation from the 4 average figure.

ACCEPTANCE CHECK 79 Planeness Example 2: The testing of levelness of substrates and A batch consisting of 500 pine planks, 50 x floors is briefly mentioned here. For more 100 mm (for floor battens) may have a moisture content of 12 %. The number of detailed information, reference is made to samples is 50. It has been agreed to use an GSO Floor facts (Gulvfakta). electric resistance meter with insulated Notice, it is very important to agree upon electrodes penetrating 1/3 of the thickness on what requirements shall be fulfilled, and the broad side in the centre of the planks ± how to test fulfilment of requirements. In only one test per plank. case reference is made to different test The individual test results are entered and methods, it will not be possible to compare computed as indicated in table 8. results. The general requirement to floors is that they must be plane and level. Planeness is The starting point is class Standard, and defined in such a way that all points of the the requirement is that 95 % of results fall floor fall within the same plane which may below 12 + 0.3 x 12 i.e. below 15.6 %, be level or may be sloping. Deviations considering that the requirement is may show as cavities or as elevations. A unilateral (requirement to maximum level floor is a floor where all points fall moisture content only). It is evident that within the same plane and the plane is level this requirement is fulfilled as only one test at the same time. Deviations from this are result, corresponding to 2 % falls outside defined as floor slope. the interval. Normally, planeness falls within ± 2 mm In case the requirement is Quality it is when compared to a 2 m straightedge (and required that 95 % of results fall below 12 ± 0.6 mm when compared to a 250 mm + 0.2 x 12, i.e. below 14.4 %. Four test straightedge), see figure 137. results, corresponding to 8 %, fall above the Planeness requirements are not only upper limit. Considering this quality applicable to the floor surface but also to requirement, it is obvious that the batch the substrate, i.e. the upper side of floor must be rejected. battens in the case of suspended floors and the substrate itself for other floor types.

Table 8 Registering moisture test result. Notice 0.25 m asymmetric moisture graph. 0.6 mm Wood % Number Accumulated Cavity moisture number content % 7 Cavity 8 9 IIIII 5 5 10 0.6 mm 10 IIIIIIIIII 10 15 30 Elevation 11 IIIIIIIIIIII 12 27 54 12 IIIIIIIII 9 36 72 13 IIIIII 6 42 84 Elevation 14 IIII 4 46 92 15 III 3 49 98 Figure 137 Testing planeness by the use of 16 I 1 50 100 straightedges 250 mm and 2000 mm respectively. 17 18

80 ACCEPTANCE CHECK Testing and testing equipment Elasticity Testing tools are straightedges with a A certain degree of elasticity is accepted in length of 2 (2mm high legs) and 0.25 m wooden floors. However, the elasticity (0.6 mm high legs). should not be excessive as this may result in When controlling planeness, first annoying vibrations, for example shaking compare floor with the side of straightedge furniture or chinking noise from porcelain without legs. Push straightedge across the in cupboards caused by persons walking on floor in order to detect irregularities. Check the floor. whole floor area, but pay special attention A precondition for the establishment of a to areas along walls and in front of windows stable floor is the correct functioning of and doors. When irregularities are detected, support systems for floor battens. The turn round the straightedge in order to make supports must be strong and it must be it rest on the legs. Irrespective of possible to fix the supports properly to the placement, the maximum distance between battens. The taller the support is, the higher floor and straightedge must not exceed 4 are the requirements to stifness/inelasiticity mm and 1.2 mm for 2 m and 0.25 m of the same in order to reduce deformations straightedges respectively. Further, the caused by traffic on the floor. When using straightedge must rest on both legs ± very tall supports, i.e. supports exceeding otherwise the planeness requirements are 100 mm, it is recommended to use inelastic not fulfilled. materials such as bricks or concrete for the The distance between floor and lower part of the support (in stead of more straightedge is most easily controlled by elastic materials such as plastic). Soft board use of a testing brick with a thickness bricks are generally carried out in corresponding to 2 x the tolerance, for dimensions as indicated on page 13. example a 4 mm brick when checking Floors on floor battens: When tolerances of ± 2 mm, and a 1.2 mm brick dimensioned in accordance with tables 4 when checking tolerances of ± 0,6 mm. and 5, a deflection of maximum 2 mm (caused by walking) is accepted. The deflection is either measured along the centreline between two battens, or on a batten halfway between two supports, see figure 138.

Maximum deflection 2 mm

² between battens or between supports ²>

Figure 138 The accepted tolerance for deflection on a floor on battens is 2 mm between battens and between supports.

PLANENESS 81 WOODEN FLOORS AND BR REQUIREMENTS

The Building Regulations 1995 define the Chimneys following requirements to wooden floors: Wooden floor coverings with a thickness exceeding 30 mm may be brought into close Escape routes contact with outer side of a brick chimney Floor coverings in escape routes, assembly wall (minimum 228 mm wall or similar, for rooms and in shops with a floor area example a lining). In the case of steel exceeding 150 m2 shall be suitably fire chimneys, a distance of 50 mm between flue resistant class Dfl± s1 (class G floor pipe and boards must be observed. coverings). This requirement may be met when using for example 21 mm tongued and Moisture insulation grooved floor or a wooden flooring with Only general remarks - reference is made to permanent fireproof bonding to non- SBI Direction 178 concerning moisture combustible base. insulation in buildings. The use of wooden coverings with a thickness of less than 21 mm and without a Sound insulation permanent fireproof bonding to non- The Building Regulations do define combustible base shall be tested in requirements to sound insulation in storey accordance with d NT 007/DS 1063.2. Also partitions, and consequently requirements see Wood 38 ± Wood and Fire (Træ 38, Træ og to impact sound etc. brand).

Fireplaces The floor shall be constructed of a non- combustible material or covered with a non-combustible cladding extending 300 mm in front of closed fireplaces and 500 mm in front of open fireplaces. Also the material must extent minimum 150 mm to either side of the fireplace opening.

82 BR REQUIREMENTS TERMINOLOGY

Boards Dispersion glue Commercial name for converted (sawn) Type of glue where the siccative is evenly timber with a thickness of minimum 16 mm distributed in the solvent. When used for and minimum 75 mm in width ± floors, the siccative is often based on acrylic corresponding to minimum 12 x 68 mm for resin or PVA and the solvent is water. planed boards.

Burr Elastic layer A fin of concrete, for example from a A layer inserted in a floating floor between formwork joint or a fin left when using a the floor covering and the load carrying straightedge for levelling wet concrete. subfloor in order to achieve the desired flexibility in the floor. Calibrate Testing instruments shall be calibrated in order to secure that test results are correct. EPDM In principle, the calibration is carried out Special type of rubber (Ethylene Propylene by comparing the instrument in question Diene Monomer). with a more accurate instrument. In most cases is only a matter of adjusting the instrument reading to make it correspond Fishplates with the reading on the ´master´ A joint between wood members carried out instrument, otherwise it may be necessary by nailing (or screwing) an additional piece to work out a table or a graph which will of wood on either side of the two members indicate how test result can be converted to to be joined, see page 46, figure 61. the correct values. HDF Compression High Density Fibre board is a Compression of fibres in a piece of wood homogeneous wood fibre board causing permanent deformation. compressed even more than MDF. The density of HDF board is approximately Continuous 870-1070 kg/m3. Continuous indicates that a piece of wood or a building component continues Insulation joint uninterrupted through an openeing , for Insulation joints are used to separate floors example floorboards through a door from adjacent building components such as opening. columns and walls in order to prevent damages, for example caused by moisture Depression expansion. Local subsidence of the surface. Levelness Dilatation joint Levelness indicates that a floor is plane and A joint specially designed to absorb that the plane is level. Deviations are movements in building components and detected as floor slope, see figure 141. elements, for example in floors.

Unsupported butt joint Unsupported butt joints are are end to end joints which are not supported, for example end to end joints between floorboards. Figures 141, Deviations from level are detected as floor slope.

TERMINOLOGY 83 Load distributing board/pressure Planks distributing layer Commercial name for converted (sawn) A layer which in floating floors accept the timber with a thickness of minimum 50 and load and distribute it evenly on a larger minimum 100 mm in width ± surface, for example a particle board corresponding to minimum 43 x 92 mm distributing the load on insulation straightened and planed planks. Floorboards substrate. are very often referred to as flooring planks. However, the use of this term is misguiding Local defect Areas with uneven surface, for since the boards do not have plank example caused by burrs or cavities. In dimensions. wooden floors a local defect may be the level difference between neighbouring floor PVA boards or blocks, see figure 139 PolyVinyl Acetate is commonly used in floor glues. MDF Medium Density Fibre board is a Quarter sawn homogeneous wood fibre board made of Boards are radial cut from the centre of the compressed/glued fine wood fibres. The tree. It produces the distinctive silver density of MDF board is approximately ribbon effect (in oak) across the whole 640-720 kg/m3. board. Annual growth rings form an angle greater than 45 degrees. True quartered OSB boards producing the best features will have Oriented Strand Board are boards made of the angle on or very much closer to 90 wood filaments cross bond in order to give degrees the board greater strength and dimension stability Radon Radioactive gas existing underground. Since Piling sticks the gas emits radiation, it is important to When stacking boards or planks it is prevent the gas from entering buildings. important to insert thin sticks between the layers in order to allow the air to circulate Regenerate freely. Regeneration of the hair harp in a hygrometer or in a thermo hygrograph is Plain sawn carried out in order to maintain the hair¶s Also referred to as ´crown sawn´ or change in length when exposed to ³through and through´ is obtained by moisture. sawing tangentially to the annual rings. Often gives a flamy look on board faces Ship plank joints caused by the cone-shape of the trunk. Special joint made with loose fillet or caulking compound in order to make the floor look like a ship¶s deck. The joint is Planeness often carried out in colours contrasting the Planeness indicates that all points of the floorboards. floor are positioned within the same plane which may be level or sloping. Deviations are defined as depressions (cavities) or elevations, see figure 140. °Shore A Shore A expresses the hardness of a material (for example elastometric compounds). The higher the value is the harder is the material.

Figure 140 Testing planeness. Deviations are defined as cavities or elevations.

84 TERMINOLOGY . LITERATURE Straightedge A completely straight board or rail used as reference when assessing planeness of surfacedefects Danish Building Research Institute (SBI): Tolerance Tolerance defines limits for deviations ‡ Testing methods in building accepted. It is common practice to use a investigations. Erik Brandt, SBI-direction symmetric tolerance, i.e. the deviation may 170, 1990. be positive or negative, for example ± 2 ‡ Sound insulation in buildings - new mm. buildings, J0rgen Kristensen, SBI-direction . 172, 1992. ‡ Sound insulation in buildings - old »Wash board« buildings, J0rgen Kristensen, SBI-direction Regular repeated unevenness of the floor 173, 1992. surface where boards are cupping caused by ‡ Moisture insulation in buildings, Nils expansion of the underside of the board, see Erik Andersen and others. SBI-direction figure 142. 178, 1993. Wash board - cupping ‡ Single Family Houses - design, SBI- direction 189, 1997. ‡ Wet rooms, Erik Brandt, By and Byg Direction 200, 2001. The Wood Industry Advisory Council: Figure 142 Wash board caused by cupping ‡ WOOD 32, Plywood, 1991. ‡ WOOD 36, Wood fibre boards, 1993. ‡ WOOD 37, Particle board in building construction, 1994. Warping ‡ WOOD 38, Wood and fire, 1995. Warping indicates that the four corners of ‡ WOOD 47, Wooden floors 2 ± the choice a board or a block do not lie in the same plane (typically caused by twisting of the of and maintenance, 2001. wood). ‡ WOOD 50, Wood ± quality and characteristics, 2003 Packed base Hands on leaflets: Referring to shocking up systems. Any combination of packing pieces is referred to ‡ Moisture in wooden floors on top of as a packed base. heavily insulated ground supported floors. (13)950224 ‡ Ground supported floors with wooden floors on battens and with heating pipes, (13)980924 ‡ Water damage in wooden floors, (43)930113 ‡ Caulked joints in wooden floors, (43)990923 ‡ Swelling of wooden floors caused by (construction)moisture, (43)991123 Others: ‡ GSO Floor facts (Gulvfakta) Gulvbranchens Samar- bejds- og Oplysningsrad. ‡ FSO Caulking guide, Fugebranchens Samarbejds- og Oplysningsrad, 2004.

LITERATURE 85 SUBJECT INDEX

Acceptance check, p. 79 Floating floors, p. 4, 39, 54 Air gun nails, p. 18 Floor battens - distances, p. 44 Aspects related to sound, p. 38 Floor battens, p. 11 Floor battens, p. 11,47 Bitumen felt, p. 13 Floor construction, p. 6 Boards, p. 83 Floor heating systems, p. 32 Burr, p. 83 Floor heating, p. 31 Floor on battens, p. 4, 38, 43 Calibrate, p. 83 Floor on joists, p. 4 Capacitive moisture meter, p. 75 Floor types, p. 6 Caulking compound, p. 41 Floorboards, p. 7 Chimneys, p. 82 Flooring cardboard, p. 15 Chipboard screws, p. 19 Flooring nails, p. 18 Click joints , p. 21 Foam plastic, p. 15 Clips, p. 21 Compression, p. 85 Glue, p. 20 Concrete slab, p. 16 Glued floors, p. 5, 59 Continuous, p. 83 Gluing bitumen felt, p. 20 Cork dust sheet, p. 15 Gluing entire face, p. 20 Cork rubber, p. 15 Gluing T & G , p. 20 Cracks, p. 74 Cupping boards, p. 74 HDF, p.83 Curved boards, p. 51 Impact sound reducing materials, p. 15 Data-logger, p. 76 Insulation joint, p. 40, 83 Depression, p. 84 Insulation materials, p. 13 Dilatation joint, p. 40, 83 Dispersion glue, p. 83 Joints, p. 40, 71 Joist distance, p. 44 Elastic layer, p. 83 Joist floor, p. 16 Elasticity, p. 81 Electric resistance meter , p. 77 Laminate floorboards , p. 10 End grain wood blocks p. 10 Laying instructions, p. 43 EPDM, p. 83 Levelness, p. 85 Escape routes, p. 82 Load distributing board, p. 83 Expansion pressure, p. 74 Local defect, p. 83

Finishing nails, p. 18 MDF, p. 84 Fire places, p. 82 Measuring, p. 81 Fish plate, p. 83 Moisture barrier, p. 14

86 SUBJECT INDEX Moisture barrier, p. 14 Moisture insulation, p. 82 Screed, p. 16 Moisture measuring in concrete, p. 78 Screws, p. 17, 19 Moisture measuring, p. 75 Ships plank joint, p. 42, 84 Monta-flex, p. 19 "Shore A´, p. 84 Mosaic parquet, p. 9, 65 Shrinkage, p. 22 Movement profile, p. 42 Soft blocks, p. 13 Sound insulation, p. 82 Nailed floors, p. 5, 59 Spacers, p. 24 Nails, p. 17, 18 Squeaking floors, p. 18, 73 Non-suspended floors, p. 4 Staples, p. 18 Straightedge, p. 84 OSB, p. 84 Stress relief groove, p. 46 Support distances, p. 43 Packing pieces -distances, p.47 Suspended floors, p. 4 Packing pieces, p. 12, 44 Partial repairs, p. 72 10-board measurement, p. 24 Parquet blocks, p. 8 Testing equipment, p. 81 Parquet boards, p. 8 Thermo hygrograph, p. 76 Parquet floors, p. 64 T-nails, p. 17 Parquet tiles, p. 9, 65 Tolerance, p. 85 Piling wood , p. 84 Plain sawn, p. 84 Unsupported joint, p. 51,83 Planeness, p. 80, 84 Planks, p. 84 Veneered boards, p. 10 Plastic foils, p. 14 Plata-Flex, p. 19 Warp, p. 85 Pressure distributing layer, p. 83 Wash board, p. 85 Pressure shrinkage, p. 74 Wet rooms, p. 36 Psychrometer, p. 76 Wood block floor, p. 68 Wood expansion, p. PVAc, p. 84 22 Wood veneer floorboards, p.9 Quarter sawn, p. 85

Radon, p. 84 Regenerate, p. 84 Renovating, p. 70 Repairs, p. 72 Rubber cork, p. 15

Sand, p. 16 Sanding, p. 71

SUBJECT INDEX 87 The book has been elaborated by the Danish Building Research Institute in collaboration and The Wood Industry Advisory Council in collaboration with: e

The Confederation of Danish Industries Casco Glue A/S Dana Glue A/S Ditas A/S Faxe A/S Fugebranchens Samarbejds- og Oplysningsrad GS Trapper og Gulve Gulvbranchens Samarbejds- og Oplysningsrad H0rning Parket Fabrik A/S Timberman Denmark A/S Junckers Industrier A/S Knudsen Kilen A/S Kahrs Danmark A/S Moland Byggevarer A/S ITW Construction Products ApS Rockwool A/S Skandinavisk Timport ApS Sunds Paneler/Parket A/S Tarkett Danmark A/S Thermisol A/S Tool-Matic A/S Trip Trap Denmark A/S Vibopan v/Novopan Traindustri A/S Woodfloor A/S Manuscript: Senior researcher civil engineer Erik Brandt, By and Byg, Danish Building Research Institute Edited by: The Wood Industry Advisory Council Graphic planning: Trine Preisler Drawings: Peter Nielsen Concept & illustration Photography: Per Jacobsen Photography and Digital Studio Print: Gøtze Grafisk, Herning

Copyright © 2004: Wood Industry Advisory Council 3. edition, 1st print, June 2004

Copying only allowed with permission from: The Wood Industry Advisory Council Lyngby Kirkestreede 14, 2800 Kgs. Lyngby Phone 45 28 03 33 Fax 45 28 03 30 [email protected] www.top.dk

ISBN: 87-90856 59-7 The handbook demonstrates thoroughly tested methods for the laying of wooden floors and describes such technical conditions which must be fulfilled in order to construct wooden floors correctly. The book has been elaborated by The Danish Building Research Institute and The Wood Industry Advisory Council.

Translation into English: Karsten Lundager, University College Vitus Bering Denmark

WOOD INDUSTRY ADVISORY COUNCIL