“The Basics of Brickwork Details”

Glen-Gery’s Brickwork Techniques Seminar Series: “The Basics of Brickwork Details”

CAUTION: This document is intended for use in conjunction with the Seminar Presentation: “BASICS OF BRICKWORK DETAILS.” Understanding many of the concepts and details presented in this document requires further explanation which is provided in the seminar. Also, the documents listed below provide additional information that should be understood before attempting to apply the information in this document to specific applications.

Reference List 1. Seminar: Basics of Brickwork Details

2. Brick Industry Association Technical Notes on Brick Construction: (www.bia.org) #1 – All-Weather Construction #3 – Overview of Building Code Requirements for Masonry Structures #7 – Water Penetration Resistance – Design and Detailing #7A – Water Penetration Resistance – Materials #7B – Water Penetration Resistance – Construction and Workmanship #8 – Mortars for Brick Masonry #8B – Mortar for Brick Masonry – Selection and Controls #18 – Movement – Volume Changes and Effect of Movement, Part I #18A – Movement – Design and Detailing of Movement Joints, Part II #20 – Cleaning Brick Masonry #21C – Brick Masonry Cavity Walls – Detailing #23 – Efflorescence, Causes and Mechanisms, Part I of II #23A – Efflorescence, Prevention and Control, Part II of II #28 – Anchored Brick Veneer – Wood Frame Construction #28B – Brick Veneer/Steel Stud Walls #36 – Brick Masonry Details – Sills and Soffits #36A – Brick Masonry Details – Caps and Copings, Corbels and Racking

3. National Lime Association (www.lime.org) Lime-Based Mortars Create Watertight Walls

4. The Masonry Society (www.masonrysociety.org) TMS 402 Building Code Requirements for Masonry Structures

5. Glen-Gery Corporation (www.glengerybrick.com) Brickwork Design Profile 4t1, Cleaning New Brickwork Brickwork Design Profile 4t2, Masonry Construction Recommendations Brickwork Design Profile 4p7,Glen-Gery Glazed Brick

6. ASTM, International C 270, Standard Specification for Mortar for Unit Masonry

This publication is intended solely for use by professional personnel who are competent to evaluate the significance and limitations of the information provided herein, and who will accept total responsibility for the application of this information. To the extent permitted by law, Glen-Gery Corporation disclaims any and all responsibility for the accuracy and the application of the information contained in this publication.

THERMAL MOVEMENT OF BUILDING MATERIALS PART ONE: Movement COEFFICIENT MOVEMENT 0.000001 in/in/ºf in/100 ft/100ºf There are four basic causes of 7/16" movement in masonry materials: 3.6 Brick Masonry (11 mm) 1. CHANGES IN TEMPERATURE 1/2" 4.3 Lightweight CMU 2. CHANGES IN MOISTURE (13 mm)

CONTENT 5/8" 5.2 Dense CMU 3. FREEZING EXPANSION (16 mm) 3/4" 4. DEFLECTION: 6.0 Structural Concrete (19 mm) Elastic and Plastic (creep) 13/14" 6.7 Structural Steel (20 mm) THERMAL MOVEMENTS 1-9/16" Every material expands or contracts 12.8 Aluminum (39 mm) as the temperature of the material changes, typically expanding as its temperature increases and contracting Figure 1 as its temperature decreases. Different materials expand and contract at Figure 1 different rates when they undergo is not determined by the difference Mortar, concrete, and concrete similar changes in their temperatures between the maximum temperature masonry units also exhibit relatively (Figure 1). When discussing wall sys- and the minimum temperature. In the major shrinkage movements as they tems, changes in the sizes of materials case of expansion, the amount of dry during and immediately following are of particular concern when they movement is actually determined by construction. If, after initial drying, occur in the plane of the wall. When the difference between the maximum materials containing Portland cement discussing wall systems, differing rates temperature and the temperature of concrete become wet, they will and directions of expansion or contrac- the wall when it was built. Similarly, in expand. As they dry again, they will tion of adjacent building materials are the case of contraction, the amount shrink. also of concern. of movement is determined by the Brick masonry, on the other hand, Brick veneer can expand and difference between the temperature does not shrink as it cures and dries in contract approximately 7/16" per at which the wall was built and the the wall. Brick masonry has an initial 100 feet per 100º F temperature swing minimum temperature. moisture expansion that is not (kt = 0.000004 inch per inch per ºF). reversible, just as is the shrinkage of When calculating the expansion or concrete products as they cure is not contraction of a brick veneer using this MOISTURE MOVEMENTS reversible. As with concrete products, factor, it is important to remember the Moisture affects all porous masonry this change in size is accommodated effects of the sun on materials. The materials, including brick, mortar, con- in design.This expansion occurs as energy from the sun’s rays raises the crete masonry units, and stone, but in completely dry brick (typically fired in temperature of a material well above very different ways. These effects must excess of 1800º F) are exposed to the the air temperature: On a day when be considered when a combination of moisture (humidity) in the air outside the air temperature is 32º F, the these materials is used, such as when the kiln. Some brick expand more than energy from the sun can raise a wall’s brick rests on a concrete foundation, others during this period. Many temperature to above 100º F. The brick veneer units are used with block expand so little that the expansion is temperature of the wall is what is back up, and when brick and architec- insignificant. Most moisture expansion important. The sun can raise the tem- tural concrete products are used in occurs during the first two months perature of dark materials to 160º F or the same wythe – bands of precast after leaving the kiln. For most design more and lighter-colored materials to concrete or architectural concrete purposes, a factor of moisture expan- 120º F and these values should be block in a brick veneer. sion of ke = 0.0005 inch per inch may used in design. Because a wall facing After their initial mixing or casting, be used. As the moisture expansion of north or nearly so receives little or no mortar, poured-in-place concrete, brickwork is in the opposite direction sun in the Northern Hemisphere, the and concrete masonry units shrink as of the drying shrinkage of concrete or temperature of such a wall rarely the curing of the Portland cement CMU, the differential movement may exceeds the air temperature. proceeds. This is an unavoidable be significant. Composite masonry We often forget that buildings are consequence of the curing of concrete sometimes fails to perform properly rarely constructed at either 140º F or products and is accommodated in because of these opposing move- 0º F and that the amount of movement design. ments. When composite systems are

MOVEMENT JOINT

VENEER AND CAVITY WALL REINFORCING used, the placement of movement joints in the brick and control joints in VENEER AND CAVITY WALL MOVEMENT JOINT the concrete or CMU must receive REINFORCING additional attention. Control Joint Joint reinforcement is typically placed in the bed joints of concrete masonry to help control shrinkage cracking. If joint reinforcement and control joints are placed properly, cracking should be limited to the control joints. This reinforcement can be either the “truss’’ type or the “ladder’’ type. Truss-type 3-wire reinforcement, which has the third wire in the brick Movement Joint masonry bed joints, should not be used unless the wall system is designed as a composite wall with a Figure 2 Figure 3 grouted collar joint. In cavity or veneer wall systems, truss-type reinforcement Figure 2 can transfer forces to the brick CALCULATING THE AMOUNT tensile, compressive, or shear stresses wythe, forces which may cause OF MOVEMENT from developing. If large stresses are damage to the mortar joints or loss of not generated, cracks cannot occur. A Figure 3 embedment of the wire. Note that Actually, we are not really interested movement joint is a discontinuity in the ANY three-wire system may cause in the amount of movement! Rather, structure – a break in the fabric of the difficulties when laying the two wythes because the widths of movement joints building – that allows movement to if one wythe is completed before the are usually arbitrarily set, we are inter- occur and prevents the build-up of other; therefore, the “eye and pintle’’ ested in determining how far apart the stresses. In most brick veneer system is preferred (Figure 2). If brick movement joints should be placed. structures, the only evidence of a is laid in stack bond, horizontal joint Brick Industry Association Tech movement joint is a very thin vertical or reinforcing must be placed in the bed Note 18A addresses movement joint horizontal band at the face of the wall. joints of the brick wythe to inhibit spacing with this equation: The exposed portion of this band is cracking of the continuous (vertical) S = [w • e] ÷ [ke + k f + k t ∆T] usually an elastomeric sealant which head joints. Where, prevents rain, snow, debris, and small S = spacing between adjacent plants and animals from filling the move- joints in inches ment space or entering the structure. FREEZING EXPANSION w = width of the movement joint in inches One of the decisions that the Freezing expansion occurs when designer must make is how wide this clay masonry units saturated with e = extensibility or compressibility of the sealant/filler band may be without unduly disturbing water are frozen and the temperature the eye. Usually, designers limit the of the frozen, saturated units goes ke = coefficient of moisture expansion, in./in. widths of the joints to 3/8" to 1/2", below 14º F. The coefficient of about the width of the mortar joints freezing expansion is k = 0.002 inch k f = coefficient of freezing expan- f sion, in./in. (Usually ignored) surrounding the movement joint. This per inch, but, since proper design decision is a key ingredient in the does not allow masonry to become k t = coefficient of thermal expansion, in./in./ºF equation used to calculate the spacing saturated, the coefficient of freezing of movement joints. To a degree, wider expansion is usually not included in ∆T= change in temperature of the brickwork,ºF joints allow greater spacing between the design equations. joints and narrower joints require closer There are at least two conditions spacing of joints.Movement joints more that must be checked; the temperature than 3/4" wide are not recommended. DEFLECTION change between the construction tem- The sum of the elastic deflection perature up to maximum wall tempera- In most building construction a and the plastic deflection of members ture and the temperature change movement joint must include a sealant, supporting masonry must be limited between the construction temperature a backer rod, and a compressible filler to the lesser of 0.30" or L/600. down to minimum wall temperature. material. Always use sealants which are capable of accommodating the calculated movement without failing. MOVEMENT JOINTS These sealants should comply with the Movement joints in the brickwork requirements of ASTM C 920. Check should be placed at regular intervals in with your sealant suppliers for their the structure to help prevent large recommendations, as some very pop-

ular construction sealants do not bond well to masonry products. Be sure to Relative Expansion take into account all materials to which Crack the sealant must bond (i.e., brick, concrete, window frames, flashings, shelf angles or metal caps) since some must be primed before certain sealants are applied. Sealants generally perform best when the ratio between the width of the sealant and its depth is about 2:1. Beads of sealant applied in a fillet or butt configuration have a much reduced service life. A backer rod must be present to support the sealant during installation Relative Expansion and tooling while also providing a bond break between the sealant and compressible filler. Backer rods may not be necessary if the sealant does not bond to the compressible filler and the filler provides adequate support for the sealant. Backer rods are usually smooth, closed cell foam ropes that Figure 4 are larger than the joint and which are forced into place before the sealant is installed. Compressible fillers are installed to keep mortar or other material from filling the joint. The compressible filler may be installed during construction to prevent mortar from Figure 4 filling the joint during brick laying and reducing the movement capacity of the joint. These fillers must have a compressibility equal or greater than the maximum compressibility of the sealant, which is generally no greater than 50%. Many filler materials are available, including premolded rubber and plastic.

HORIZONTAL MOVEMENTS When the cyclical movements associated with horizontal expansion and contraction have not been considered during design, corners are Figure 5 particularly susceptible to cracking caused by tensile and shearing interleaving of brick resulting from Since expansion cracks often occur stresses. Figure 4 shows what can staggered head joints. In stack bond near corners, one logical location for a happen when the brick veneer expands work, poor tensile bond strength movement joint is at the first head joint – a crack develops at the corner. must be overcome by installing from a corner (Point #1 in Figure 5). Cracks may also develop at continuous reinforcement at no more Unless they are installed as a remedial windows, doors, changes in cross than 18 inches on centers, vertically, measure, movement joints are rarely section, or other weak points in the in the bed joints of the brick masonry found at corners, primarily for aesthetic masonry. The effects of cyclical as per ACI 530 and other building reasons. They are usually placed two movements are magnified when the Codes. This technique is also effec- to ten feet from the corner (Point #2 brick are laid in stack bond because tive whenever tensile strength must in Figure 5), where, in buildings with the tensile bond between the mortar be increased, regardless of the shelf angles, the movement joint may and the brick is not great; much of bond pattern. coincide with the window jambs to the strength of a wall comes from the help to disguise the presence of the

joint. When the veneer is supported on shelf angles, vertical movement joints may be placed virtually anywhere the designer decides that they are needed EXPANSION because the horizontal movement joints at the shelf angles divide the facade into relatively small, discrete, (a) regular sections. If the masonry is carried across openings by lintels, it is best to avoid placing vertical movement joint at the jambs of the openings. Instead, place B A them several feet from the jambs. Expansion Joints B EXPANSION Although movement joints are often (b) placed at the jambs with no ill effect – this detailing “works” – more conserva- Figure 6 Figure 7 tive design suggests placing the movement joints well away from jamb Figure 7 lines and the ends of the lintels. Figutemperaturere 6 at different rates to the back-up, the back-up system Do not place vertical movement because thinner, shorter sections must also be tied to the columns in a joints at the end of lintels. will warm faster than taller thicker manner which transfers wind loads sections.To reduce the likelihood of while allowing vertical move- Another critical point for crack con- cracking, movement joints are placed ment to occur. Construction tolerances trol is at offsets in walls, such as at A at the point where the cross-section are rather fluid and the attachment in Figure 6. Since A is short and rigid, of the wall changes (Figure 8). of the veneer to the column at a it can easily be cracked by the rota- In steel or concrete frame struc- movement joint should include a tie tional effect caused by the movement for the end of each veneer panel. of the two long walls. A movement tures, one typical movement joint joint should be placed at the inside location is at a column. This location Although movement joints in brick corner. The only time this is not true is not always necessary but may be veneer and control joints in the block is when the next movement joint in helpful to the contractor. The brick back up may align, it is not necessary each long wall is less than 10 feet from veneer must be anchored to the col- for them to do so, and they can be the corner. umn in such a way to allow vertical placed where ever the design dictates. and horizontal movements and to One advantage of aligning the two Long sections of masonry with allow the movement joint to function. joints is that it may make construction punched openings with heads One method is shown in Figure 9. and inspection easier. supported by lintels should include Since the ties between the veneer vertical movement joints to guard and the back-up transfer wind forces against shear cracks forming at the top corners of windows (Figure 7) or diagonal cracks forming at piers. Stresses develop as the masonry below the windows, which is restrained from moving by the presence of the foundation, expands and contracts less than masonry above the windows. As the band of masonry above the openings is much longer than the bands of masonry between the openings, the total expansion is much greater and shear stresses are generated. These stresses are relieved when the crack forms. Remember, if lintels span the heads OPENING of the windows, the movement joints should not coincide with the window EXPANSION JOINT jambs. Where adjacent sections of a wall (a) (b) differ in height and cross-section, the sections will respond to changes in Figure 8

Figure 8 5

MOVEMENT JOINT AT COLUMN VERTICAL MOVEMENTS strength, the intensity and duration of (Elastic and plastic loading, and the size of the member. MOVEMENT JOINT AT COLUMN deflections) As an example, if we assume that As mentioned earlier, movements a 10 story building with 10 feet story heights has a creep value of 0.05" per occur in the vertical direction as well as Control floor, the total creep would be 0.5". (Shrinkage) the horizontal, but while horizontal wall Joint If there were shelf angles supporting Shear segments tend to move at both ends Anchor from a stationary midpoint, vertical wall brick veneer at every floor level, the segments expand upward from rela- expansion gap under each shelf angle tively stationary supports and contract will close permanently by 0.05" (almost downward toward these supports. 1/16"). Added to other movements, this shrinkage reduces the serviceability of Veneer Many building codes limit the vertical Movement spans of brick veneer to 30 feet or the structure if not considered during Joint less. The practice of supporting brick design. If shelf angles are placed every veneer on shelf angles at each floor three stories (30 feet), then each gap level requires the installation of move- would close by 0.15" (more than 1/8") Figure 9 ment joints beneath each shelf angle. from column shortening alone. Creep The shelf angles themselves should be also affects concrete beam deflections, Figure 9 sized and anchored to carry imposed which are in addition to the column loads such that total displacement of shortening. the toe of the angle is limited to L/600 or 0.3", whichever is less. One detail for a supporting shelf angle is shown in Figure 10. The expansion gap size is dictated by the Anchor total amount of movement caused by: 1. Thermal expansion and contrac- Weepholes Flashing taken to exterior of tion of the veneer below. wall Sealant 2. Moisture expansion of the Shim as required brickwork below. 3. Freezing expansion of the brickwork below. Foam backer rod SPECIAL SHELF ANGLEFace of beam or slab 4. Elastic deflections of the shelf UNITS angle, supporting beam, span- Compressible filler Cavity drel, slab edge and columns. 5. Plastic deflections (creep) of Figure 10 vertical members, particularly in concrete masonry and reinforced concrete buildings. 6. Thermal frame movements. SPECIAL SHELF ANGLE UNITS Note: A steel frame erected at 80º F will shrink substantially if exposed to 30º temperatures in the winter. Creep is the continuing shortening of a member under constant loading – a plastic deformation. Creep usually occurs over a relatively long period of time. When Portland cement concrete products, which are particularly prone Figure 10 to creep, are fully cured, members loaded in compression actually squeeze or flow together. The speed of this flow is greatest at first, and continues, but at a decreasing rate, for several years. The total amount Soldier Stretcher of creep depends on the concrete Figure 11

Figure 11

SHELF ANGLES AND LINTELS Metal snap-on coping Sealant Precast-concrete While both are usually formed with and or stone coping backing rod hot-rolled steel angles, shelf angles Drip and lintels are very different. In both Drip Drip Flashing Anchor cases the weight of the masonry Sealant veneer above the steel angle bears on Sealant the angle. When a lintel is used, the weight of this masonry is transferred to the jambs of the opening below the lintel. Shelf angles act in a different way: Shelf angles do not rest on the jambs of the openings below, they are attached to the building frame. Thus the weight of the masonry above a shelf angle is transferred the building frame and the masonry in the jambs of Figure 12 the opening below carry no load other than the weight of the jamb itself. cut since over-cutting in either direction creates a weak point in the brick which LIPPED BRICK Figumayre 12 result in cracking the lip itself. When all of the vertical movements Also, corner brick cannot be cut in the are taken into account, the movement field unless a mitered corner is accept- gap at each shelf angle is usually able. The presence of the shelf angle about 1/2 inch thick (tall) when built. may also be disguised by corbeling the Figure 13 The shelf angle is 7/16 inch or 1/2 inch course of brick immediately above the angle to create a shadow line. thick. Thus, the thickness of the Figure 13 horizontal joint at the shelf angle is an inch or more thick. Although the PARAPETS movements discussed may narrow this gap somewhat, the gap is wider than Parapets require special considera- corresponding bed joints and is visually tion because they are exposed to more environmental changes – temperature objectionable. Special shelf units Ties (lipped brick) detailed in Figure 11 can changes, wind loads, and rain and eliminate this objection (Note that, in snow – than the walls below. Both the most instances, lipped brick cannot magnitude and the rate of change of be used with lintels). Remember that the environmental factors are greater special lipped corner brick are needed for parapet walls than for the walls at corners. Extending the flashing to below. Also, the direction of change Weepholes the face of the brickwork is difficult may be very different. Therefore, verti- Flashing when lipped brick are used and some cal movement joints in the parapet should be no more than 20 feet apart Concrete fill designers turn the lipped brick upside or grout down to allow easier placement of the unless each masonry wythe is rein- Damproofing flashing. This practice should be forced. Corners and offsets remain avoided since the lip is very close to critical locations that must be protect- the toe of the shelf angle and contact ed. Figures 12 and 13 show several Figure 14 may damage the brick. Another option suggested details concerning proper is to place the flashing and weepholes parapet wall design. Note that these figures do not show all elements of in the mortar joint above the first Figureexternal 14 flashing. Masonry copings either detail. course of brick resting on the shelf tend to be more susceptible to water angle. If this option is used the space Figures 12 and 13 show an air penetration, require through-wall between the angle and the flashing space which is continuous past the flashing, and may require more should be filled with mortar to support roof edge. This eliminates a shelf angle maintenance because of reliance upon the flashing and prevent collection and reduces the likelihood of efflores- sealants in movement joints between of water. cence and staining. The vertical legs adjacent members. Note that covering Glen-Gery makes lipped brick to of metal caps should cover at least the exposed face of the backup with match both molded and extruded four inches of the masonry. The metal an impervious membrane for the entire brick. Lipped brick should not be field coping shown in Figure 12 forms an height of the back-up wythe may trap impervious cap which is considered an moisture within the back-up wythe and

reduce the durability of both the masonry and the impervious membrane. If a membrane does cover the back-up wythe, the height of the parapet should be no more than 16". Other coping materials can be used with these systems. Cast stone, con- Window crete, natural building stones, terra cotta and brick must be laid with a Sealant flashing, must be anchored to the structural back-up, and must have a soft joint placed between the bottom of the coping and the top of the brick Brick Sill veneer. Always separate veneers from elements rigidly attached to the back- up system. Through-wall flashings are required not only because these copings are permeable, but because the Flashing many joints of these copings may deteriorate and fail, allowing moisture penetration. Masonry copings should incorporate the largest units available to limit the number of joints at the top of the wall and thus the likelihood of moisture penetration. The mortar joints between large rigid caps such as stone Figure 15 or concrete should be raked and caulked to reduce potential moisture penetration at bond breaks. Flashing be so saturated with water that the the face of any insulation or other should be installed immediately below water appears inside of the structure. materials applied to the face of the the cap. The cap should include a Four inches of brick masonry, the usual back-up. nominal thickness of a brick veneer, will minimum 15º slope and, on the low A further development of the not Figurekeep 15the water out all of the time; side, project past the face of the wall drainage wall system is the rain screen the mass of masonry is not so great below with a drip a minimum of 1" wall. Water may be driven through that it can absorb all of the water to from the face of the wall. Stone, brick masonry because there is an air which it is exposed before penetration concrete, and cast stone copings may pressure difference between the two through the brick wythe occurs. contain soluble components which, in sides of the brick wythe. If there is no the absence of a flashing under the Designers have long recognized this air pressure difference, very little water coping, may stain the masonry below. characteristic of single-wythe veneers will pass through the masonry. In a rain and have developed the “drainage screen system, the air space is vented wall” system to accommodate it. at the top and bottom and horizontally The concept of the drainage wall is compartmentalized to allow any differ- PART TWO: relatively simple (Figure 14): A space ences in pressure to be equalized WATER PENETRATION is maintained between the back of the quickly. Once pressure differences are brick wythe and the face of the back-up eliminated little water will pass through For most of our history, brick material so that water which penetrates a properly designed and constructed masonry has been used as a structural the veneer cannot reach the back-up brick wythe. Rainscreen walls are material, laid in multiple, tied wythes to system. As there are places where very specialized in both design and provide the major support for the floors there are paths to the back-up system, construction and are beyond the and roof of a structure. Only in this at shelf angles and at the bases of scope of this publication. century has this changed; the use of walls, for instance, a flashing is reinforced concrete and steel framing installed to collect water at these has eliminated the need for load- places. So water does not fill up the air DESIGN AND SPECIFICATION bearing brick masonry and we com- space (cavity), weepholes are placed OF DRAINAGE WALLS monly use only a single wythe of brick on top of the flashing at the base of One of the most effective methods masonry to clad buildings. Multiple- the air space to drain water from the of reducing the amount of water that wythe brick masonry is water resistant wall. Critical to the performance of this hits a masonry wall is to use over- because of its great mass. It must rain system is maintaining a clear space hangs to protect the walls. This is very hard for a very long time before between the back of the brick wythe particularly easy when pitched roofs 12" or 16" or 24" of brick masonry can and the face of the back-up system or are used. Gutters and downspouts

should be installed where other means of roof drainage have not been Weepholes detailed. When the roof is flat, over- hangs can be incorporated by extend- Flashing end dam ing the ends of the joists, but a more typical detail is a gravel stop or parapet wall. When a gravel stop is used, it is important that the gravel stop be high enough to retain water on the roof until it can drain off through the roof drains. Parapet walls (and garden walls) must be capped to close the top of the wall. While brick masonry caps are very attractive, they present many Flashing end dam opportunities for leakage and deterio- Flashing with ration unless they are designed and Weepholes installed very carefully. Masonry caps end dam must be pitched to drain, have full Area of potential joints, and be securely anchored to the Weephole water penetration wall below. A flashing and adequate if optional lower Optional flashing is NOT anchoring system must be placed lower installed below masonry caps (Figure 13). In flashing addition, a minimum 1" overhang and drip notches are recommended for all masonry caps. Glazed brick must not Optional lower flashing be used to form a cap. When a metal cap is used, 1) the top must be pitched to drain, 2) the vertical legs of the cap must Figure 16 cover at least four inches of brick masonry, and Figure 16 3) a drip must be formed at the bottoms of the vertical legs water is directed away from the building. FLASHINGS Down spouts should not be discharged (Figure 12). Changes in the details of the wall at the base of the wall, but, at a mini- cross-section often allow materials to The primary function of a window mum, should be directed onto splash bridge the air space, providing a path- sill is to keep water draining from win- blocks and away from the building. dows or other impervious materials way for water to reach the interior of from running down the face of the The key to the drainage wall system the building. This routinely occurs at masonry. Many other siding materials is to keep water from moving from the shelf angles, lintels, load-bearing floor as well as windows and doors absorb back of the veneer to the face of the slabs, and at grade. To prevent this little or no water, allowing most of the back-up. The space between the flow of water, a flashing, a flexible, water to flow over the sill or cap below. veneer and the back-up – the air impermeable material, is installed. The All sills must have a minimum pitch of space – must be kept clear of mortar flashing both collects water and pro- 15º (about 1/4" to the inch), must and other debris so that water has no tects materials behind and below it incorporate a drip edge or notch and path from the veneer to the inside of from this water (Figure 14). Counter should have as few joints as possible. the structure. Wider air spaces, two flashings, flashings under caps, and Wind pressure on flat sills tends to inches, for instance, are easier to keep flashings under sills pr increase water penetration, leading to clean than narrower spaces and are deterioration of the sill or surrounding recommended by many authorities. materials. Because of the absence of One way to keep the air space clean is sunlight on north elevations, very deep by clearing the mortar droppings from sills receiving large amounts of water the cavity by placing a board in the will remain wet, promoting organic cavity and drawing it out as each tie growth and the accretion of dirt. As location is reached. Spreading the with wall caps, a flashing must be mortar so that the inside of the bed is placed under all sills (Figure 15). thinner than the outside will reduce the volume of mortar droppings. Proprietary event water fr It is important to pitch the grade systems are also available to help around the structure so that surface maintain a clear air space.

entering the veneer. Flashings over window, door, and louver heads, flashings at the bases of walls and at shelf angles, and flashings over and under other building materials all collect water and prevent it from entering the remainder of the structure. Except for counter flashings, which are usually installed in a reglet at the face of the wall, these flashings are usually installed as through-wall flashings –

remain so. Because the basic materials CHIMNEY SECTION and fabrication are so expensive, these materials are now little used. Most of Clay flue liner the flashings installed today are plas- Sealant tics, fabric composites, and composite Flue liner Chimney cap metal flashings. A very common flashing material that should be avoided is

Flashing Airspace PVC (poly-vinyl-chloride). PVC flashings have a limited life span, as short as five years in a wall system that is expected CMU Airspace to last for many years. Other materials, such as bitumen polymers, EPDM, Heat resistant caulking Chimney flashing w/ weeps fabric composites, or thin metal composites with cores of either aluminum Roof flashing or, preferably, copper, are preferred. Weepholes Shingles Neither #15 or #30 building felt nor Chimney flashing polyethylene sheeting may be used Roof flashing for flashings. Shingles Although most flashing details will Cricket show the flashing forming a drip at the face of the wall, this is only possible if one of the rigid flashings is used. Cricket Plastics, composites, and thin metal composites cannot be formed into a Figure 17 Figure 18 drip and are difficult to hold in a straight line. One popular option is to require the mason to extend the flash- Figure 18 ing beyond the face of the wall and Figure 17 CHIMNEY SECTION then cut it flush to the face of the wall. The details of many flashing manufac- turers indicate that the flashing should be held behind the face of the wall about one-half inch. When this is done, the water will run under the flashing and into the core holes or back into the wall. Avoid these details. Continuous flashings, such as occur End dams at shelf angles and at the bases of walls, must be lapped and sealed in Stepped flashing accordance with the flashing manufacturer’s instructions. This often involves the use of a special mastic or adhe- sive. Do not use roofing cement. Care Figure 19 must be taken at inside and outside corners to insure that water cannot bypass the flashing and enter the wall system. Discontinuous flashings, such flashings laid in or attached to the Rigid flashings for single wythe chim- as those over a lintel, should extend back-upFigure which 19 then drop down at neys can be formed with short overlap- beyond the end of the lintel. The ends least eight inches, run horizontally, and ping flashings. Flashings in multi-wythe of discontinuous flashings must be then pass through or under the brick chimneys must incorporate flashings turned up into a head joint, forming a wythe to the outside. which terminate in the back-up. dam to prevent water from running Flashings from the face of the chimney Flashings in masonry above from the end of the flashing and back to the roof may be attached to the stepped roofs, above bay windows, into the wall (See Figures 16 and 20). and around chimneys are often face of the chimney or tucked below Flashings above curved arches or attached to the face of the wall with the through-wall flashing (Figures 17 pitched roofs are often omitted a reglet. Flashing systems in these and 18). because there is no obvious way to locations must include through-wall Traditionally, heavy copper, lead- install the flashings. One practical flashings that collect water from behind coated copper, and stainless steel method is to install short lengths of the brick wythe (Figures 17 and 18). were the materials of choice and they

through-wall flashing above and along stresses may be high. Type “S” mor- the line of the arch or lower roof. tars may be helpful when floating is a Each flashing has end dams and the problem or when the bricks have a upper flashings overlap and shield very low initial rate of absorption those below, protecting the building Concave (suction). Type “S” mortars have lower (See Figure 19). A single level of flash- joint water penetration resistance, are not ing can also be used successfully if the as workable, and are more expensive area of masonry between the flashing than Type “N” mortars. and the arch is small. Vee joint JOINT TYPES WEEPHOLES The configuration of the mortar Weepholes provide a path out of the joint affects the resistance of the joint wall for the water collected by the to water penetration (Figure 20). flashings. The easiest way to form a Grapevine Concave, vee, and grapevine joints weephole is to space open head joints joint provide the highest resistance to water 24" apart, directly on top of the flash- penetration. All other joint profiles ings. Weepholes located a course or should not be specified for exterior more above the flashings are of little work. benefit. Many designers do not like the Figure 20 shadow created by using open head joints for weepholes and a number of vents, screens, and multi-celled GLAZED BRICK WORKMANSHIP devices are available to disguise the Because water cannot escape presence of these weepholes. All of through the face of a glazed brick, the these may be spaced 24" apart. evaporation of water through the face STORAGE OF MATERIALS Cotton wicks – not nylon or other syn- of the masonry is severely limited and All masonry materials, including the thetics, they do not “wick” – may alsoFigure 20 large amounts of water may be masonry units, cement, lime, sand, be used. Three-eighth inch cotton trapped in the veneer. This reservoir of coloring pigments, water, ties, and clothesline works well, particularly water may affect the durability of the anchors, must be stored off of the when draped over the first set of ties masonry and it must be eliminated. ground to prevent damage, contami- above the flashing. Wicks should be The loss of surface evaporation must nation, or absorption of water. It is space no more than 16" apart. Do not be balanced by designing an air space particularly important to cover the use 3/8" plastic tubes; they are easily at least two inches wide and incorpo- mortar materials to prevent hydration clogged during construction. Some rating open head joint weepholes at and to cover the masonry units and designers and contractors placed two the bases of air spaces and open head sand to avoid water absorption and to four inches of unbroken pea gravel joint vents at the tops of air spaces. freezing during cold weather. at shelf angles, at lintels, and at the Individual weepholes and vents should base of the cavity to prevent weep- be no more than 24" apart horizontally. holes from being clogged by mortar Obviously, it is mandatory that the air WEATHER EXTREMES droppings. This can be an effective space be kept clean so that air can When it is very hot or very cold, technique unless the volume of mortar move freely. special care must be taken during con- droppings is such that a continuous struction. Also, temperature extremes barrier of mortar is formed on top of MORTAR are exaggerated when it is windy. the gravel, or mortar dropping on the When it is hot and dry, mortar readily gravel bridge the airspace above the There are two rules for mortar loses water to evaporation, quickly top of the flashing. When this occurs selection: becomes unworkable, and loses its the effective freeboard of the through- 1) No one mortar is best for every ability to bond to any masonry unit. educed and water can wall flashing is r purpose and Mortars with the ability to retain water, have easy entry to the interior of the such as mortars containing hydrated structure. Care in material selection is 2) Use the weakest mortar type that lime, should be used. If a brick has a important because fractured stones will do the job. field measured initial rate of absorption can cut the flashing. Also, the weight Portland cement/hydrated lime (suction) in excess of 30 grams, this of the gravel may stretch and tear the mortars provide the best resistance loss of bonding ability is accelerated. flashings, particularly at shelf angle to water penetration and Type “N” In hot, dry conditions, these brick bolts or at lintels where the flashing is Portland cement/lime mortars provide may have to be wet before laying. not continuously supported. A number the greatest water penetration resis- Immersing a cube of brick in water the of proprietary systems also serve this tance. Type “S” mortar may be used day before laying or use of perforated function and claim to avoid the disad- where greater flexural tensile strength hoses works well. The brick must be vantages of gravel. is important; primarily where bending saturated but surface dry before laying.

When it is cold, the bricks and FULL HEAD AND BED 5. Always wet the wall thoroughly mortar components must be kept from JOINTS before applying chemicals and freezing, the work must be covered keep it wet – with water or the with insulating blankets, and, depend- It is vitally important that joints be cleaning chemical – during the ing upon conditions, the work may full. If head and bed joints are not full cleaning process. of mortar, the effective thickness of the have to be enclosed and the space 6. Rinse the wall thoroughly. heated. Follow the recommendations wall is reduced, thereby decreasing the contained in BIA Technical Note #1. water penetration resistance. Poor construction techniques often lead to EFFLORESCENCE unfilled joints. While specifications MIXING MORTAR usually require full joints, the only sure Efflorescence is a deposit of soluble salts on the surface of the masonry. Mortar makes up about 20% of the way to get full head joints is for the specification to require that one head of Without water, efflorescence cannot area of the face of a wall laid with stan- occur. The thrust of preventative mea- dard modular size brick. Since changes each brick be buttered with mortar and the brick then be shoved into place. sures for controlling efflorescence is to in the color of the mortar will change control water in the masonry because the appearance of a wall, consistent efflorescence is only the symptom of and accurate proportioning of mortar CLEANING the underlying problem – the presence materials is important. This consistency The clays, shales, additives, and of water. In most cases, these salts and accuracy cannot be achieved by are extremely soluble in water and simply counting the number shovels of coatings used to manufacture a brick all determine how a brick must be acids or special chemicals are not sand that go into the mixer. A proce- needed to remove them; only an dure must be developed to assure that cleaned. The presence or absence of a colored mortar or manufactured or absence of water and the passage the same volume of sand is put in the of time are needed. mortar mixer for each batch of mortar. natural building stones all affect how Cubic foot boxes and five gallon buck- a masonry wall must be cleaned. New buildings sometimes become ets are often used for this purpose. Consult the manufacturer of each stained with efflorescence. This stain- Specific requirements for mortar mixing masonry product before establishing ing is called new building bloom and is are found in ASTM C 270, Standard or accepting a cleaning method. usually the result of water entering Specification for Mortar for Unit As time passes it becomes more unprotected walls during construction, Masonry. difficult to remove hardened mortar, but may also be caused by the water particularly when the mortar is in large in mortar or grout. New building bloom lumps. Brush down the wall with a stiff is best handled by waiting for the MORTAR LIFE bristle brush each time the scaffold is building walls to dry over a heating or Mortar becomes stiff in two ways: raised and at the end of each day or cooling season and then allowing rains 1) Water evaporates and the mortar is shift to remove large lumps. Type “N” to wash the salts from the walls. no longer plastic and 2) the chemical mortars should be cleaned within The appearance of efflorescence in reaction with water (hydration) causes fourteen days of laying the brick; Type older buildings is a symptom of a the mortar to become stiff or hard. The “S” mortars within five to seven days. change in the way that the structure chemical reaction reaches initial set in The bucket and brush method is handles water. Eliminating the flow of about two and one-half hours and the preferred method. Pressure water into the masonry will solve unused mortar must be discarded at washers, while they may be useful for problems with efflorescence. that time. Water may evaporate at any wetting and rinsing can cause immense A common time for efflorescence time and cause the mortar to be come damage if used to apply chemicals or is in later winter or early spring. This stiff and unusable. Rather than throw to remove smears and snots. happens because water tends to the mortar away, water can often be remain in walls for a long time at this added to restore the plasticity of the Remember: time of year – there is no extra heat to mortar. This is called “retempering.” 1. Never use muriatic acid. evaporate the water – and the water Two notes of caution: Retempering 2. Chemicals that are not acidic will has a long contact time with the build- may lighten the color of mortar and not remove hardened mortar. ing components. Thus, chemicals that retempering will reduce compressive might be considered “insoluble’’ in strength slightly. While any change in 3. Metal tools of all types may water reveal their slight solubility the color of the mortar is a concern, damage the walls. because of the long contact times. changes in compressive strength are 4. Test all materials and methods Again, the solution is to deny water usually minimal and the workability thoroughly. Allow the test areas access to the walls. Because the gained by the addition of water far out- to dry before accepting a chemi- location of the dew point is moved, weighs the small loss of compressive cal and method. efflorescence may also appear after strength when laying a veneer (a non- HVAC system change over. loadbearing wythe).

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