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TECN CALPUBLICATION RESEARCH DIVISION SERIES NUM B ER 8 ISSN : 1324·56001S8H:0731022033

SOME IMPORTANT FACTORS Consideration should al so be given to so il OFTEN OVERLOOKED IN HOUSE conditions. Heavy clay, sandstone or shale all have their own drawbacks, as does the presence of fill, CONSTRUCTION AND THE ROLE and it would be wise to familiarise yourself with the OF TIMBER IN BETIER BUILDING s T • T I block's history if at all possible. FORES TS With the price of an average house in the Sydney -- u.* ..,.... Aspect area now exceeding $100,000, excluding land, the purchase of a new home is probably one of the most A north-easterly orientation is normallyconsidered ideal important long-term commitments made by most and it would depend on lifestyle whether the front or the Australians. All too often though, the old adage rear of the house faces in that direction. Long southerly 'purchase in haste, repent at leisure' applies to many walls are best avoided where possible because little sun will fall on them, particularly in winter and, even with purchasers of new or existing homes. good circulation of air, algae will often form on brick walls and pathways. While consumerlegislation has neverbeenstrongerthan it is now, with special indemnity schemes and builders Vege tation being required to provide long warranties against major structural faults, purchasers should still ensure they are While there is no argument that trees, shrubs and other aware of the basics of good building practices. vegetation are a desirable feature of any home, the planting of inappropriate species on a suburban block, Whether purchasing an existing home, contracting a or indeed on any property, will often far outweigh any project or contract builder, or undertaking the job as an subsequent advantage of shade and outlook. owner builder, timber, after the founda tions, will probably be the single most important structural The decision to plant Australian natives because of their co m ponent of yo ur new home and so me basic drought resistance is an ad mira ble one in the push to un derstanding of the product, its behaviour under conserve our precious water resources, but the siting of different circums tances, and its role in better building some trees close to houses, most notably a number of our will assist the purchaser in making more informed eucalypt species, will often prove a costly mistake. decisions. Simply, the 90 to 150 cm blue gum, spotted gum or THE SITE blackbuttof today will be tomorrow's 20to 30 metre plus giant. The quantity of water needed by trees of this size Often buyers of land or existing houses fail to see far past is enormous and as the average home owner will still a pleasant leafy outlook, a shiny kitchen, or innova tive water lawns and gardens, many of these trees ' roots will decorator items. While it may appear to be stating the stay near the surface and will travel to cool moist areas obvious, the site is one of the most expensive and easiest underneath paving, footings and slabs with obvious places to go wrong. consequences. This phenomenon is not only limited to our native species of course. The result of planting many Generally, a reasonably level block in as high a position popular trees, particularly species such as liquidamber, as possible will ensure minimal site costs and far less rubber or umbrella trees close to hou ses and swimming chance of drainage difficulties. It will also minimise the pools is often not appreciated until it is too late. By the risk of overshadowing by neighbouring buildings or time the problem of continually blocked roof guttering, trees. ground storm water drainage, sewerage pipes and pool filters is recognised, it will usually be too late to convince an inappropriate method of cons truc tion resulting in your local council that eithe r the trees or yo u mu st go. cons iderable cutting of the land wi th resultant altera tion Unfortunately, the problem will not always be yours of natural drainage patterns. While the amo un t of fill alone. Some thought should also be give n to your that can be used is now more limited than in the past, its neighbours who, while no doubt appreciating some use will often result in substantial site cos ts that are summer shade, w ill probabl y not than k you for invasive normally not included in standard building contracts. roots, cons tantly dropping leaves and twi gs, a feature of Similarly, the cost of drainage and earth retention caused man y native species, or for a heavil y shadowed yard in by cutting into the site is normally cons idered to be a site winter. cost and would be considered an extra. Points to be considered if a concrete slab is to be used. State Forests of New South Wal es ha s a number of brochures available that will provide guidance regarding 1. Ensure the site is reasonably level. If it ha s to be cut the planting of native species . Alternatively, local and! or filled, considerable unexpected costs ma y be nurseries sho uld , providing you ask the right questions, incurred. be able to offer expert advice. 2. Makesure before the slab is poured thatthe waterproof Bush es and garden bed s against the house ma y block membrane is properly lapped and sealed at all joints ventilation openings or cover slab ed ges sufficiently to and around services, that it is not holed during allow the ingress of water or insect pests through weep construction and that it is properly turned up around hol es or other gaps between brickwork and slab. A good the perimeter. rul e of thumb is to build the hou se off the ground and if you must plant against the walls, try to steer clear of 3. Ifit is necessary that an y part of the underslab area be sh rubs wi th dense foliage or, in the case of concrete slabs, filled, ensure the soil is correctly compacted and that ens ure that gardens remain well below the top of the its area and depth does not exceed the provisions set concrete. out in AS 2870 Pt.1 or an y special conditions im posed by a number of local Councils. SLAB VERSES SUSPENDED TIMBER FLOOR

For a numberof years, concrete slabs have been a popular 4. Finally, if possibl e, request that a fixed price for site method of domestic construction because with an ideal cos ts be included in yo ur quotation and subseque nt site they may offercost ad vantages wi th less organisation building contract. of trades for the builder. However, it's a sad fact of life that ideal blocks of land are few and far between. In 5. The recommended curing time for a concrete slab manyinstances, particularly in hill y areas,slabs are often under ideal conditions is approximately one month per 25 mm thickness. Therefore, floor coverings, timber, etc. may be expected to absorb moisture from the concrete until they reach equilibrium with each other.

Suspended floors Timber floors havebeen with us for many years and offer a practical alternative to slab on ground construction.

While bo th sys tems have their place, timber floors offer a number of real advantages.

1. Where an ything other than a level building block is encountered, there is no necessity to alter the land's natural drainage pattern by excessive excavation of the site. While there wi ll obviously be a need to carry out foundation work and bricking to floor level, thi s will usually be offset by savings on excavation, Exampleof extreme excauat ion (cut)for cOl/crde slab drainage and earth retention works. 2 J 2. Less drainage will be required. However, ground As noted earlier, the BCA no longer stipulates the water mu st still be directed away from the perimeter clearances required between subfloor members and the of the house to ensure the underfloor area remains finish ed soil level. or does it now set out the dry (preferably below 18%). This is usually achieved requirements for subfloor ventilation, relying instead on with the installation of adequate ventilation and say ing that the subfloor must be well ventilated. simple agricultural drains on the high side. Adequate ventilation is critical to the health of all buildings and their occupants. Therefore, an absolute 3. In SW, the Building Code of Australia (BCA) has minimum recommendation for subfloor ventilation is replaced Ordinance 70 as the primary building code. 2100 mm?perlineal metreofexternal wall. All ventilators In an attempt to standardise building requirements mu st be dispersed evenly throughout the external and across Australia, a number of changes and internal wall areas to ensure adequate cross flow. The recommended ventilator area should, in fact,be increased compromises had to be made. The new Code no wherever possible. longer stipulates a minimum height for timber subfloor members above the finished soil surface. In the past, terracotta vents were common but it was However, while the BCAdoes not requirecompliance found they weresusceptible to being easilyblocked. The with Australian Standard AS 3660 - 1993 "Protection more accepted method now is to leave open mortar of Buildings from SubterraneanTermites-Prevention, joints around the Detection andTreatmentof Infestation", this Standard perimeter wall or requires a minimum clearance of 400 mm (or 16") bronze mesh vents between the finished soil level and the lowest pointof that provide a ------~ - - an y subfloor member. This recommendation is for ------~------substantial air flow . ------ideal conditions and it is suggested that wherever There are now also a possible this clearance be increased, if for no other ".'~ '" number of timber i .," 1"'0...... - • • .. .:" reason than to enable easy access to the under floor . . . . ~,, "-: .... products that enable area for inspection and the installation and the clear spanning of Bronze mesh ventilator maintenance of services such as heating, plumbing, floors overconsiderabledistances. These productsshould telephones etc. be given careful consideration because notonlywill they ensure better air flow under the building, they also 4. If the site is naturally damp and the problem can't be providethe opportunity tomakebetteruse of the available easily remedied, a waterproof membrane can be laid under floor area which can then be cleared of intrusive over the soil surface. If ponding occurs at the low piers with associated cost savings. side, drain holes in the foundation wall can be easily cut or drilled. In any case, every effort should be Ifbuying an existing house it would be wise to carefully made to identify the cause of such a problem and to inspect below any wet areas such as shower cubicles, rectify it as quickly as possible. This is, of course, far and bathrooms generally, for signs of mould, fungus, or easier to accomplish when you have easy access discoloration of timbers that may be an indication of under your house. water leaks.

VENTILAnON TERMITES o matter how dry the under floor area may appear to o matter what materials are used in construction, be, there will always be some eva po ration from the soil. termites are a potential hazard to all buildings in the In the case of a concrete slab, if insufficient care has been wa rmer areas of Au stralia. Th e most comm on taken with the installation of the waterproof membrane subterranean termites require dark and dampness to or ifinsuffi cient provision has been made for ventilation sur vive so where they have to emerge from the soil, they throughout the subfloor area of a suspended concrete or bu ild 'tubes' between that and their food source. The timber floor, mu sty odours ma y occur. In severe cases, presence of these 'tubes' is not alwa ys easy to detect in humidity may be highenough to enable the development dark corners or in mortar joints between bricks. A trick of fungal growth on floor members, coverings or walls to make inspection easier is to apply a band of white (see Technica l Publication o. 11 "Ventilation under around all piers and on the inside of foundation Timber Floors"). wa lls.

3

------A vast amount of research into timber properties and products has been carried out over the years with the result that it is now readily accepted that most houses built using common practice timber sizes and methods of construction are substantially over-designed when account is taken of the load sharing occurring in an average timber hou se frame. It is unlikely that this situa tion will change because, while in the ory mu ch sma ller sizes could be used, it is considered by most builders that it is impractical to handle and fix timb ers of the smaller possible dimensions. The range of structural timbers and timber products is almost as vast as the resource itself which, in New South Wales, amounts to more than 3.5 million hectares in State Forests alone.

The product possibilities from our forest are almost unlimited, from the more traditional sawn unseasoned Mud plastering and galleries built by subterranean termites illobtauung , native pinesand otherimported , access to a suspendedfloor to ourownplantation grown, kiln dried radiata pin e and other manufactured products such as pl ywood, The correct installation of ant capping at the top of particleboards, gluelam and LVL. detached piers and of continuous capping along foundation walls and attached piers isa critical operation SPECIES GROUPS during construction. Sawn hardwoods Ant caps are not intended to be impassable barriers. The numberof species occurring naturally in New South Rather, they are installed so that an y insect pests trying Wales is not reflected in their availability (see Technical to cross them will have to show themselves. Ifcontinuous Publication 0.10). The unique properties of the various capping is notcorrectly installed and joined, insects ma y species though, and the range of sizes, grades and be able to breach the barrier in areas not able to be easily products available, make our hardwoods a valuable inspected, with obvious results. resourceprobably unmatchedanywhereelse in the world.

There are three basic materials used for ant capping ­ The range of products available, or possible, copper, galvanised steel and zincalume. Of these, the is almost limitless. From traditional sawn timbers, to most widely used is galvanised steel. Copper, while an high quality tongue and and sheet excellent material,is usuallyconsiderably moreexpensive products such as and , to dried solid than the other two, and practical experience relating to structural timber and manufactured products such as the joining of zincalume has usually proved to leave gluelam and LVL, our hardwood forests provide a somethingto be desired. Itis imperative thatantcapping remarkably versatile and abundant renewable resource. be continuously and correctlyjoined withsolderor a like ma terial. Reliance on the use of pop rivets and/ or silicon Cypress sealant is not recommended. For many years, cypress was the most widely used flooring material in this State and in sawn form is still TYPES OF CONSTRUCTION used extensively as a wall and roof material in In recent times a number of new construction materials the western are as of ew South Wales. Among its more and methods have become available and some have desirable properties are its high durability classification been hea vily promoted with var ying degrees of success. (Class 1) and its resistance to termite attack. This native The ran ge of stru ctural materials, from timb er and steel is traditionallysold in an unseasoned or 'green' frames, to full brick and tilt up slabs and everything in state and has performed excellently as a framing timb er. betw een is conside rable. However,still the most popular Some difficulties, however, have arisen in the case of and wide ly used material by far is timber. cypress flooring where it has been milled to a tongue and

4 grooveprofileandinstalledstill ina greenor unseasoned subject of catastrophic impact or seismic damage. In condition. In recent times this problem has been many of these instances, where rigid materials such as addressed by many of the more progressive cypress masonry have subsequently had to be demolished, the sawmillers with the installation of drying facilities and timberframes havebeenrecovered, oftenwithrelatively modern equipment. 'Gauged' or 'sized' cypress little difficulty or expense. framingandaccuratelygraded,seasonedcypressflooring from reputable suppliers are nowfirst rateproducts,the While most homes are now built using prefabricated equal of any other species. frames and roof trusses, there are still a goodnumber of 'stick built' houses constructed throughout New South Radiata pine Wales and many builders still prefer to use traditional Originally known as monterey pine (Pinus radiata) this unseasoned hardwoods or cypress pine. In addition, species was introduced into Australia in the late 1800's some frame manufacturers continue to use unseasoned together with a number of other softwood species and Douglas- (Oregon). has since become our single most important softwood, displacinganumberofimportedtimbersin the structural A poor understanding of the material often results in market. InNew South Wales, all radiata for structural problems further down the track. Unseasoned timber purposes is dried and marked with its relevant stress will, to varying degrees, shrink as it loses moisture. grade and these days the majority of it is mechanically While this has to be accepted as a fact of life, it is graded which removes any possible doubt of human something relatively easy to overcome. error or subjective assessment. There are two ways of cutting timber, back sawn and SHRINKAGE IN FRAMEWORK quartersawn(Figure1),andthedegree of shrinkagethat applies to mostbuildingtimbers is considerablymorein Withthealmostuniversaldemandfor driedor 'seasoned' back sawn'boards, Therefore, while probably difficult, wall and roof framing, the incidence of shrinkage or quarter sawn timber shouldbe specified if the timber is distortion of timber members is not what it once was. to be green or unseasoned. However, it should be appreciated that some minor movement in timber may still occur and that a few simple precautions will minimise, if not almost totally eliminate,anynoticeablemovementinyourtimberframe. Back cut

All buildings will 'move' to a certain extent. Soil will inevitably expand and contract with changing weather conditions,brickworkmay'grow',concrete 'shrink',steel willexpand and contractwithtemperature changes and in the case of metal framing may cause shadowing on internal lining materials due to condensation. The severity of any of these occurrences will very much depend onbuilding practices and physical and climatic conditions.

Timber too is not immune to movement but with the demandfor dryor 'seasoned' framing, movementcanbe expected to be negligible. However, it must be Figure 1. appreciated that some movement of timber members may still occur and while the occasional door may jamb It should be appreciated that, while in some timber inwetweather, this is usuallytheresult of poorbuilding species shrinkage in both width and thickness may be practices rather than the materials used. Timber is an extremelyforgiving materialand while it maybe forced noticeable, longitudinal (length) shrinkage is unusual. to move, for instance by soil movement, it will, because GOOD NAILING PRACTICE of its naturalresilience and unlike most othermaterials, compensate and recover when conditions return to While goodnailingpracticeswillnotpreventshrinkage, normal. This has been demonstrated many times over the correctpositioning of fixings can certainly minimise the years where timber framed homes have been the the effect. For instance, in a brick veneer home the

5 externalframes willhave wallboard (or plaster) onlyon will always be toward the fixing point and the more one side. Therefore, the nails securing the studs to the material between that point and the edge of the timber, top and bottom plates should be positioned as close as the greater the proportional movement willbe. practicable to the wallboard side. Shrinkagemovement will be toward the fixing point (or nails) so most movement will be on the side with the greatest area of unrestrained timber that is, on the non-critical side. Where both faces of a wall are important, such as on an internal wall, the fixing point should be centralised. Naturallythis practice wouldbe appliedto noggins too. As corners are usuallythemost critical areafor cracking it is best (withunseasoned timbers) not to fix wallboardto Min. 10 mm clearance the studs at the corners but certainly it should be well around allhorizontal secured to the noggins and plates which, as referred to openings, egsoffits, earlier, will not shrink noticeably in a longitudinal windows, etc. direction.

Good nailingpractice (placement close to critical side) ~ ('-Lining s top/bottom plate <­ board stud orequidistant noggin

(if appropriate) Figure 3. ~op~itt~m S :: ::::::::;E plate ::? stud OTHER TRADES AND SERVICES stud Careful attention should be paid to the installation of services, particularlywhere theyinvolve any breaching Figure 2. or cutting of structural timber members. It is an unfortunate fact of life thatsomeinstallers of plumbing, Wherethecladdingisbrickveneerandwhereunseasoned electrical, air-conditioning andother services,.havelittle bearers and joists and possibly wall plates are used, appreciationof thenecessitynottohackor outlarge allowance must be made for differential movement sections of criticalstructuralmembersand, whilethereis between the frame and the brickwork (Figure 3). A gap considerable load sharing in the average timber frame, of at least 10 mm shouldbe left under window sills and there are points where that does not apply, for instance wherethebrickworkmeetsthesoffitliningsof theeaves. in large section, long spanning deep floor joists that While longitudinalshrinkagein thestudswillbeminimal could be easily weakened by excessive notching or the it must be appreciated that bearers, joists and top and boring of large holes in the chords and webs of truss bottom plates will all shrink in width and thickness as members which are equally critical. they dry out. Ifunseasoned deep joists are used in first floor construction a greater allowance will have to be SARKING, FLASHING AND VAPOUR BARRIERS made in that area as the rate of shrinkage will be Sarkingisa vapourpermeablebutwaterprooffabricthat proportionally larger as the dimensions of the timber is fixed immediately beneath roof covering or behind increase. However, none of this need cause any great timber wall cladding (Figure 4). Its intent is to prevent difficulty providing good building practices are anywater that maypenetrate the cladding from wetting employed in the first place. interior linings and to provide a draft proof barrier for the building. The rule of thumb thatshouldbe rememberedis that, no matterwhat, greentimber willshrinkbutifrestrainedit While sarking mustbe waterproofit must still allow the will take the pathofleastresistance. Therefore,movement free flow of vapourfromthebacksurfaceof the cladding.

6 Ifit preventsthe flow ofvapour, timber cladding, which Unflued heaters, showers, clothes dryers, cooking, and for instancehastakenupmoisture duringperiodsofwet evenpeople generate considerable amounts of moisture weather, may tend to cup as the outside face dries. It is vapourwithinbuildings. Some ofthatvapourwill move recommended that only vapour permeable building outwards through plaster, and other permeable paper shouldbe used. Polythene film, foil or other non­ materials until it disperses into the atmosphere, reaches permeable material should never be used as sarking an impermeablebarrier, or meets a surface cold enough immediately behind timber cladding. Building papers to condense. Where watervapour is able to cross a wall with fire retardation properties are also available. cavity whenthe outside temperatures are low, moisture may condense onthe back of the cold outer cladding or Note: Manufacturers' instructions regarding the use of sarking. Where this condition is allowed to continue perforated foil should be followed or they should be over alongperiodoftimetimberframes and/or cladding installedin accordancewithAustralianStandardAS 1904 maytake up this moisturewhichcouldeventuallyresult "Code of Practice for Installation of Reflective Foil in decay in non-durable species of timbers. Laminate in Buildings". While the general rule is thatvapour barriers shouldbe . Whereweatherboards are used,it is excellentpractice to positioned on the warm side of all infill insulation fix a vapourpermeablesarkingmaterialto the outsideof material, in some areas of Australia, suchas in the snow thestudsdirectlybehindthetimbercladding. Itishighly fields where daytime conditions could be the reverse of recommended that sarking be used in walls where the those at night because of heat reflection from the snow, building is subject to highwind conditions, updrafts, or expert advice should be sought from insulation wherever weatherboards are fixed diagonally or specialists. vertically. The use of sarking is not intended as a substitute for properly installed cladding andit should THERMAL INSULATION notbe installedas a principalmeansofweatherproofing. While air in a confinedspace is a fair insulator, timberis Vapour barrier to excellentbutimpractical as an infill material. However, prevent moisture the use of specifically designed and manufactured transfer from thermal insulation material between timber members interior will greatlyimprovethe comfortfactor in mostbuildings ifinstalled correctly. Vapour permeable sarking toallow There are manytypes ofinsulation, fromfibreglass batts passage of andloose fillmineralwoolandtreatedcellulose material moisture (paper), to any number of other proprietary products Figure 4. thatwhenusedcorrectlywill, to varyingdegrees, do the job expected of them. Basically though, the intent of all Where sarking is intended for use as a secondary insulation material is to slow the passage of heat by waterproofingmaterialundercladding,flashing should creatingtinypockets ofair. In these daysofrisingenergy be usedat all corners,verticaljointsandaroundopenings. costs the use of insulation in ceilings, walls and even Even though sarking is not always used under external floors is highly recommended, particularly if coupled cladding it is essential that flashing is installed in the withgood sealing arounddoors and windows andwith above areas to ensurewaterispreventedfrom penetrating the use of boxed pelmets, insulated curtains and other the wall frame cavity. As its use is only localised, non­ methods designed to slow the exchange of cold and permeable materials are usually used as flashing. heated air. Where extensive use is made of insulation and buildings are correctly designed to take advantage VAPOUR BARRIERS ofpassivesolarenergywiththe useofproperlydesigned The use of vapour barriers (Figure '4) will depend shading and heat sinks etc., considerable long-term primarily upon the climate, the intended use of the energy savings and comfort levels are possible. structure and the method of construction. Where the potential exists for considerable variation between WINDOWS internal and external temperatures, the likely incidence of water condensation on either side of wall linings is Until about 30 years ago timber was the most widely high. used window framing material; today aluminium is

7 more popular for reasons of maintenance and stability. Buildings clad with timber have a number of natural However, while aluminium has many excellent advantages, particularly in high wind areas, extreme properties, insulation is not one of them and its use in climates, highly reactive soil areas and subsidence or positions exposedto directsunlightduringsummerand earth tremor zones. Unlike other rigid materials, the in situations whereheatingis used in winterwill have a natural resilience and high strength to weight ratio of definite negative effect on building comfort. timber enables it to withstand far greater stresses and movement. EXTERNAL TIMBER CLADDING As mentioned earlier there are a number of timber There are many materials available, from New South species suitable for cladding. These are generally Wales hardwoods and preservative treated softwoods, produced in widths from 150 mm to 200 mm wide. to plywood and proprietary hardboard products. Because of the risk of movement,it is notrecommended However, as with any material, ensuring the best that boards wider than 200 mm be used, other than re­ performance of your chosen cladding will very much manufacturedtimbercladdingmaterialssuchas exterior depend upon good design, good building practice and grade . There are a number of different correct installation. surface finishes and profiles available but with the exception of radiata pine, these often vary considerably To ensure the bestpossible performance of your timber from area to area and it is recommended that the local claddingpreferenceshouldbe given, where possible, to supplier be contacted and asked for advice. designs thatenable thematerialto be protectedfrom the elements by wide overhangs such as verandas or eaves. Storage and handling This will give weatherprotection to your walls and will greatlyreduce thenecessityfor maintenancein theform As withanyvaluablebuildingproduct,seasonedtimber of painting. Critical areas with which extra care should claddingshouldbe keptclean and dryfrom the time it is be taken during constructionare endjoints, corners and received on site until it is fixed and finished. If outside wherever the timber cladding abuts doors, windows or storage cannotbe avoided the timber shouldbe stacked other suchpoints. Extra care should also be taken in all on a well drained level site at least 150 mm clear of these areas to ensure flashing and sarking is correctly ground on bearers spaced at no more than 900 mm installed and thatthe end grain of the timber is properly centres. The stack shouldbe coveredwith a waterproof sealed. membrane thatfinishes justclear of the ground to allow ventilation under the stack. The provision of a similar External timber cladding should finish at least 150 mm membrane to cover the soil beneath the stack is also above ground level (Figure 5). Ifnot, moisture uptake recommended. may eventually cause deterioration near the ground. . "'-... I/" <, ,./ <, i.-"'" <, Endslapped "" and sealed ~ Cladding, back-cut for dripedge Cover to extend below stackbut ...--f- :.--- -.... -tMin150mm not toground . ., ~ ~ -+ clearance to 4 : '. 4,; ', ground e- . A' • '. Concieie- Figure 6. Plastic covered stack.

4'" . ... : elab.«.. ". 4.fl· ~m~~TIm~m~~;:::: Painting and finishing .". Some timbers,notablywesternredcedarandpreservative 4 . treatedpine, are occasionally fixed in place and allowed to weather naturally. While the natural grey colouring FigureS. that results is considered by some to be attractive, the

8 same effect canbe obtainedwith certain timber finishes. a flat roof structure, full use of appropriately placed It is highly recommended however, that timber used permeable andnon-permeable membranes and suitable externallybe properlycoatedwithan appropriateexterior insulation material should be made. Manufacturers' stain or paint as unprotected timber will deteriorate recommendations should be sought. physically when exposed to extreme atmospheric changes. Sun, rain, wind, frost, deleterious fumes, Where a low pitched roof is unavoidable, for example shrinkage and swelling will gradually cause suchas wherethe pitchchanges for a verandaroof, there disintegration. is always the chance that rain could 'beat' up under the tiles. Where this is a possibility, sarking should be Weathering is essentially a surface effect and most considered a necessity. properties, apart from surface abrasion resistance, are hardly changed. However, weathering should not be FLOORING confused with decay which results from fungi acting in There are three basic types of timber flooring used in thepresenceof excess moistureandair overanextended Australian homes, sheet, , and period. parquetry.

Weathering protection may be provided by the Sheet application of coatings such as , water repellents, waterrepellentpreservatives or pigmentedpenetrating Sheet flooring is more often employed in the platform stains (see Technical Publication No. 3). The main system, that is the building is taken to floor level and objectiveof anyofthesetreatmentsis to preventorretard sheetflooring is laid over the entirefloor area to create a the uptake of moisture andthe absorption of ultra violet working platform. All frames are subsequently placed light. on top ofthesheetmaterial. This systemis often favoured where roof trusses are used to enable the placement of Note: Linseed oil or a mixture of linseedoil andmineral non-loadbearinginternalwalls freely withinthe building turpentineshouldneverbe used on timbercladdingas a withoutregardto subfloor construction. Manufacturers natural finish. Further information regarding timber usually recommend thattheir sheet material shouldnot cladding may be obtained in the NAFI Timber Manual be left unprotected from the weather for more than 90 Data File FP1 "Timber External Cladding". days if all other recommendations are followed. Overhang trimmed DECAY on completion Timber will be susceptible to fungal attack if any of the following four conditions exist -

1. Moisture content between 20 and 25% or more.

2. The presence of oxygen. (Timber completely saturated, submerged or 600 mm or more below ground level is rarely attacked.)

3. Temperature within the range of 5° to 40°C. A temperature range of 25° to 40° C is considered ideal for fungal attack. At higher or lower temperatures fungal attack is retarded. Figure 7. Sheet platform flooring.

4. Food in the form of unprotected nutrients must be Tongue and groove flooring present. Nutrients in the sapwood can be protected Most tongue and groove floors are 'cut in'. That is, the by preservative treatment. buildingis usuallybrought to a stage wherethe interior isprotectedfrom the weatherandthe flooringboardsare LOW PITCHED OR FLAT ROOFS thencut to fit individualrooms. While suchtimbermust Whereit is notpracticalto providefor thefree passageof be sold in a seasoned state unless otherwise agreed in air between the roof covering and the ceiling, such as in writingbetweenbuyerandseller, thatis 10-15%mc, that

9 range is relatively wide, particularlyif air-conditioning distortedbecauseofincorrectstacking,unnaturalstresses or centralheatingis to be installed. Inany case, flooring may be placed on plates or other critical should ideally be allowed to attain balance with its systems. Unfortunately, once these members are in surrounding atmosphere before final fixing takes place. placeandcovered,theyare verydifficultifnotimpossible This would usually entail the cutting of all boards to fit to properly repair without major expense. Equally, theirindividualroomsbeforeleavingthemupsidedown windows and flooring cannot be expected to perform in place to protect their top surfaces for a week or two properly if mistreated. Often these problems will not while other work proceeds. Where possible, a longer becomeapparentuntilmuchlaterandas manymayonly period of time is desirable. Ifcut and placed accurately be considered a nuisance, they may not be sufficiently thissystemshouldprovidea stableworksurfaceandnot serious to warrant major repairs or claims against the present any real hazard to tradesmen. builder. Whilethereislittlean ownercando ifpurchasing a readybuilthome, other thanvisiting other sites under Parquetry thebuilder'scontrolto see whatlevelof care is takenwith materials, if directly contracting the builder there is no In domestic construction, parquet flooring is normally substitute for letting him know from the outset of your laid as a high quality feature floor surface andis usually expectations andintentionto regularlymonitorworkin considered a job for experts. It must be laid on a solid stable base such as concrete or a timber sheet product progress. such as plywood or hardboard andwouldnormallynot be installed until most other work, particularly wet CONTROLLING BUILDING COSTS trades, have finished. Any individually fabricated materials will invariably cost more than standardlines and this shouldbe keptin CANTILEVERED BALCONIES mind when specifying room sizes, stud spacing and A number of problems with this system of construction layout etc. For example, if a platformfloor is used, non­ havebecomeapparentinrecentyears. Insomeinstances loadbearingwallstuds can be laid outwithoutregard to balconies have literally fallen off because of decay in joistsandwheretrusses are able to be positioneddirectly unprotected timber joists, occasionally with people on over or within the thickness of a load bearing stud, top them. While this is alarming to say the least, it is plates can be considerably smaller than otherwise. generallynotthefault of the timber;ratherit is the result Similarly, if rooms are able to be kept to standard wall of inappropriate building practices that have allowed sheetlining dimensions, or their multiples, therewillbe unsuitable timber species andpoor attention to detail to far less wastage. Anuncomplicatedroofline,if designed be used. The use of untreated low durability timbers in properly, canbe aesthetically pleasing andwillresultin sucha situationis a recipe for disaster. Unless all timber worthwhile savings while providing less likelihood of membersare totallyprotectedfromtheweather,AS 1684 future maintenance difficulties. Box gutters should be "The National Code" directs that a avoidedwhereverpossible,particularlyiftreesoverhang minimum Class 2 durability species or its preservative the house. treatedequivalentmustbe usedinsuchsituations. Even so, the proper detailing of timber members against It is very easy to be swept away in the euphoria of moisture should be a priority because, be it timber or buildinga newhome. Everythinghasto be justrightand even steel, if the material is inadequately prepared and a wall moved slightly or a few extra power points are maintainedthere is always the risk of eventual failure. always tempting. Ifmoneyis not a major consideration thereis norealproblem. However,while majorstructural Itwouldalso be wise, for obvious reasons, to ensure any changes are certainly best carried out during railings or balustrades in such situations are of an equal construction, extras or last minute unquoted variations or more durable species too. can oftenbefar more complicatedthantheyseemon the surface and will inevitably cost more thanexpected and CARE OF MATERIALS ON THE BUILDING SITE shouldbe keptto a minimumor avoidedwherepossible.

All too often timber willbe seenlying unprotectedfrom There is no point insisting on and paying for higher the rain or in mud and water on a building site. Where gradeframingmaterialsfor non-loadbearingwallswhen that timber is in the form of seasoned frames or trusses lower grades will be more than adequate. As long as it should be of particular concern to the prospective material such as plywood and other products are home owner. In simple terms, the reason that timber is structurally sound, there is little use specifying driedinthefirst placeis to ensureits stability andwhere appearance grades for uses where they will notbe seen critical members such as roof trusses are soaked or or are not necessary, such as in wall frame bracing etc.

10 Service areas suchas bathrooms,kitchens andlaundries • Check for squeaky or bouncy floors. This should shouldbe kept, where practicable, in as close proximity ideally be done during a period of dry weather. to one another as possible to reduce the overall cost of water and waste services. • Look for any signs of leaking pipes or floor wastes. • Wherepossible, checkthe integrityofverminproofing Whileprobablycostingmoreinitially, the use of durable wire between the outer wall and the timber frame. timbers in external situations will invariably translate into long-term savings on maintenance. • Ensure that adequate provision has been made for ventilation and that the underfloor area is clear of all SOME POINTS TO LOOK FOR WHEN PURCHASING AN obstructions. Make sureprovisionhasbeenmadefor EXISTING HOME adequate ventilation openings in internal masonry walls. The following is not intended to be an exhaustive check list. Rather, it highlights a number of major areas of Wall framing and internal interest that should be carefully examined before committing to a purchase. There are a number of • Wall framing is generally inaccessible but the use of companies and individuals that offer pro-purchase a long straight edge and a good sized on building inspection services. It would, however, be internal walls should give a fair indication of the worthwhile having your legal advisor check the terms accuracy and care taken during construction. and conditions attached to suchcontracts because some offer so many disclaimers and 'outs' thattheyoffer very • Check windows for any signs of leaking and for little protection to the client. general soundness. • Bathroomsshouldbe checkedfor evidence ofleaksin Floor and subfloor shower cubicles that are often apparent because of • Dryness of the soil. Lookfor anysigns of cracking in silicon sealantat floor or walljunctions. Inthecase of the soil that might indicate very wet soil conditions buildings on slaps, such leaks are sometimes during periods of wet weather. evidenced by musty odours or by water stains on adjacent carpets. • Staining of subfloor timbers or mould growth, • Check ceramic tiles for soundness. Sharp rapping particularly around bathrooms and laundries etc. It with the knuckles will sometimes return a hollow is advisable to use a long sharp probe to check the sound which indicates drummy tiles. This is soundnessofall accessible structuraltimbersadjacent occasionally found in older buildings (late 1960's to to these areas,particularlybottomplates,bearersand joists etc. mid 1970's) because of installation methods and materials used at those times. • Signs of termite activity. Look for evidence of mud • Look for anybows inceiling plasterboard. This may tubes in dark corners and between timber bearers indicate incorrect fixing or roof leaks and will be and joists or evenbetween flooring boards or sheets. practically impossible to properly rectify without They can be hard to detect so a very bright light is totallyremoving andreplacingthe sheetsin question recommended. if it is a long standing problem.

• The general cleanliness of the under floor area. The • Cracks in the plasterboard, extensive patching or presenceoftimberoffcuts, cardboardetc.,particularly fresh paintworkallindicatethatsomeadditionalcare ina longstandingbuildingis nota goodindicationof shouldbe taken with your inspection. care taken by previous owners. • Generally check the walls for soundness bypressing • Check the joins in the continuous ant capping. If the walllining firmly back against the frame to see if there are problemstheywillusuallybe evidentwhere there is any excessive movement. If there is, it will the capping for attached piers is joined to the more likelybe inthe fixing of the lining to the frame, continuous capping. butagainitissomeindicationofthe buildingpractices used. • Lookfor anyevidence of rustedantcappingor wetor damp brickworkabove theantcapping. This is often • Check the operation of doors and windows and a good indication of leaks from wet areas or that the ensure there are no obvious or excessive differences damp course is incorrectly installed, damaged or in the clearancebetweenthemandtheirsurrounding non-existent. frames.

11 Roof and ceiling space External • Lookfor anyobviouslydeflectingroof memberssuch • Check brickwork for soundness. The existence of as purlins, struts or bracing etc. that appear to be out cracking along mortarjoints or throughbricks could of line or obviously not doing their intended job. (If indicate a foundation problem. you have any doubts, a good builder or structural • Ensuregardensandshrubsdo notobscureventilation engineershouldbe consulted. Inthe longtermit may openings. be money well spent.) • Make sure that any gardenbeds do not come within • Check for water staining of roof members that may at least 100 mm of the top of the concrete slab. indicate roof leaks. Also look carefully at insulation • If timber clad, check the soundness of the timber, material. Quite often, particularly with fibreglass particularly at corners and where it abuts window batts, dripping water will make small holes in the and door frames and along the bottom edge of the material. lowest board. ,. ,1 • Check for any signs of light through the tiles. While • As far as possible, ensure all building debris andtree thisis to be expectedinthemainbodyof anunsarked stumps etc. have been removed from the site. I roof, if it is evident along the ridges it will indicate missing pointing that will have to be corrected. • Make sure any paths or soil are battered away from the building, that all drainage is connected and discharges to the low side of the site. • Valley boards should be checked for soundness. If the valley gutters are subject to build up of debris • Take particular note of overhanging trees or those they will often overflow or rust. that have the potential to become a nuisance.

• Roof gutters, downpipes, facias and eaves linings State Forests of New South Wales operate a Timber should all be carefully inspected for soundness. Inspection Service which, for a fee, will inspect and Gutters shouldbe free of rustandhave sufficientfall. report on any or all timber or timber components or Down pipes should flow freely and discharge to the productsfor compliancewithyourwrittenspecifications. street if the building is on the high side. Eaves and The Timber Services Branch can be contacted on facias should be well maintained and free of water (02) 9804100 or throughState ForestsRegionalOffices at staining that may indicate overflowing gutters. Coffs Harbour, Taree, Eden, Albury or Dubbo.

ACKNOWLEDGEMENTS Terry Tolhurst for revision of this publication, Joy Gardner for compiling the manuscript reproduction and Marcia Lambert for oversight and co-ordination.

This publication may bereproduced in full provided acknowledgement is made to State Forests of New South Wales. Extracts may not bepublished without prior reference to StateForests ofNew South Wales Copyright ©: State Forests of New South Wales 1995 Additional copiesmay be obtained by contacting:

Publications Officer ResearchDivision StateForestsof NSW PO Box100 BEECROFT NSW 2119

Phone (02) 8720111 Fax (02) 871 6941