Preventing and Treating Distress in Brick Veneer Cavity Walls

I S S U E 1/2016  VOLUME 33  NUMBER 1

Journal of architectural technology published by Hoffmann Architects, Inc., specialists in the rehabilitation of building exteriors. Preventing and Treating Distress in Brick Veneer Cavity Walls

Erin L. Kesegi, AIA and Robert A. Marsoli, Jr.

M asonry construction is one of – clay brick – is actually a composite the oldest methods of creating built wall system, with materials ranging structures. However, the brick wall has from steel and concrete to flexible changed considerably since the first flashings and sealant, in addition to fired clay bricks were laid nearly 8,000 traditional brick-and-mortar elements. years ago. To address problems and How and where these materials come considerations with modern brick ma- together, and why they behave the sonry, it’s important to understand the way they do, is of critical importance components of the wall assembly, how to the weather protection, integrity, they behave, and what can go wrong. and longevity of the wall assembly. Today’s complex brick cavity walls As modern masonry construction has share little in common with the solid grown increasingly complex, so too masonry construction of Romanesque has the design, detailing, and installa- church towers or early load-bearing tion of brick cavity walls become more high-rises, with their thick, stout walls. demanding. Where once a skilled With multiple layers, or wythes, of mason was all it took to achieve a brick bonded together, these historic durable exterior wall, proper con- masonry walls relied on the unified struction now demands the efforts of structural capacity of the wall thick- multiple tradespeople working in col- ness to withstand horizontal and laboration with the design professional vertical forces and to provide weather to achieve a water-tight, structurally protection. stable, aesthetically appealing masonry In contrast, modern brick veneer exterior. Prevention of water infiltra- cavity walls anchor a single wythe of tion, structural failure, and other woes face brick across an air space, typically by means of appropriate design and two to four inches wide, to a back- meticulous workmanship is the ideal, Long, vertical cracks at building corners up material. Part of a drainage system but for existing buildings, the mission may indicate underlying structural distress. that includes flashings, drip edges, and becomes timely and accurate identi- weep holes, the air space creates a fication of emerging problems, with pathway for moisture to exit the wall repair strategies that provide lasting assembly, while a steel, concrete, or solutions. masonry back-up provides structural support. Design Basics What may seem on the outside to be As reinforced concrete and steel a wall composed of a single material framing have eliminated the need for

Erin L. Kesegi, AIA, Project Architect, applies her expertise in building envelope remediation to addressing underlying causes of brick masonry distress. Project Manager Robert A. Marsoli, Jr. provides engineering services to resolve structural concerns for a range of building types, including brick masonry construction. JOURNAL

load-bearing masonry, building design the brick veneer and the back-up, such flexible plastics, fabric, and composite in the twentieth and twenty-first cen- as at shelf angles, lintels, and the base metals. Given the projected lifespan turies has evolved new approaches to of the wall, flashing, a flexible, imper- of a modern wall assembly, it’s best to waterproofing protection. Early brick meable material, is used to collect wa- avoid materials that degrade quickly, walls relied on the mass and depth of ter and drain it to the exterior. Serving such as polyvinylchloride (PVC), which the masonry to absorb rainwater and both to direct water and protect the may last as few as five years. ambient moisture and to release it brick masonry from moisture dam- Water collected by the flashings is back into the atmosphere. Given the age, the flashing is in turn protected by drained to the exterior by means of nominal thickness of modern brick counter-flashings, which are attached weeps. While open head joints in the veneers, the mass of masonry is insuf- to or directly laid into the back-up. brick course above the flashings pro- ficient to absorb and release envi- At the face of the wall, drip edges, or vide a simple, effective weep system, ronmental moisture without allowing downward bends in rigid flashings, en- vents, screens, and other inserts may water penetration into the building courage water to form droplets that be used to disguise the open joints interior. Therefore, cavity wall design fall away from the wall surface, rather and prevent insect ingress. provides for a space between the back than travel back up under the flashing of the brick veneer and the face of the and into the wall assembly. Lateral Support back-up material, so that water that breaches the brick exterior can drain Copper, lead-coated copper, and stain- Masonry anchors secure the wall as- out of the wall system without reach- less steel are the traditional materials sembly to the building structure, while ing the building interior. for flashings, and they remain the most masonry ties connect multiple wythes durable and reliable options. However, of masonry together or join a mason- Flashing System and Waterproofing these materials are expensive, so flash- ry veneer to a back-up wall composed Where transitions must exist between ing now tends to be composed of of another material, such as concrete

Typical Masonry Cavity Wall

Wall tie

Rigid insulation

Air space Vertical reinforcing bar

Brick Grout

Mortar joint Moisture/air/vapor barrier membrane Concrete masonry unit Termination bar Horizontal joint reinforcement Mortar joint Flexible flashing membrane Cavity drainage net Weep vent / weep hole Metal drip edge Sealant bed Concrete foundation Illustration: David S. Obrizzo (adapted from the International Masonry Institute Masonry Detailing Series)

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masonry units (CMU) or metal studs and shelf angles, along with adjustable walls is characterized by the type with sheathing. All of the metal acces- veneer anchors that allow the two and dimensions of the brick units, the sories for a masonry cavity wall should materials to move differentially within mortar type and tooling profile of be stainless steel and spaced at ap- their planes, while still providing an- the joints, and the coursing, or pattern, propriate intervals, as determined by chorage to resist out-of-plane forces, of the brick layout. In contemporary building codes, industry standards, and including wind and seismic pressures. brick cavity walls, the brick veneer is secured with metal wall ties to the the design professional. To accommodate vertical movement, back-up material. However, facade To control shrinkage cracks in ma- steel shelf angles (also known as reliev- designs may incorporate false headers sonry, as well as to tie multiple wythes ing angles) may be installed at intervals in the veneer to simulate traditional of masonry together and to anchor along the wall elevation, typically at coursing patterns. masonry veneers, horizontal joint re- each floor, to support the masonry inforcement is incorporated into the above a horizontal expansion joint, Brick size is standardized according to exterior wall system. Two or more allowing for vertical expansion of the “nominal dimensions,” which account longitudinal wires with perpendicular brickwork. Use of shelf angles depends not only for the size of the brick unit (ladder type) or angled (truss type) upon the type of structure, height itself, but for the completed assembly cross wires are laid in the mortar joint, of the building, size and location of in the wall system, including mortar with the longitudinal wires parallel to windows, type of masonry anchorage, joints. Bear in mind that openings, cor- the face of the wall. and a variety of other factors, including ners, and wall heights must take into building code requirements. account the dimensions and cours- Provisions for Movement ing using brick module, or increments Along with shelf angles, vertical and Building materials expand or contract based on the size of the brick. horizontal expansion joints are used to when exposed to external stresses, separate the masonry wall into seg- Mortar Joints such as changes in temperature (ther- ments and thereby prevent cracking. mal movement), moisture/humidity Regardless of the type of masonry As dissimilar materials in the assembly (moisture movement), dead and live construction, all brick units are held change in response to temperature, loads and external lateral forces (elas- together using mortar, a mixture of ce- moisture expansion, elastic deforma- tic deformation/creep). As brick draws ment, aggregate, and water that is but- tion, settlement, and creep, each will in moisture from its environment, it tered, or spread, between bricks during move according to its own tenden- will increase in size over an extended stacking. There is no single best mortar cies. Horizontal expansion joints are period of time. Most of the expansion type for all structures and situations, particularly important for masonry typically occurs in the first few months but a good maxim is to select the veneers attached to a reinforced con- after the brick is fired but continues at weakest mortar that will do the job. crete frame, as the concrete back-up a lower rate over the following years. Mortar that is too hard does not per- tends to shrink while the brick tends mit movement of adjacent brick and Another main contributor to move- to expand, a phenomenon known as can cause cracks and spalls, in which ment of brick is thermal expansion frame shortening. Composed of flexible pieces of the brick face are forced off. and contraction. Because both thermal materials, expansion joints can close Different joint types provide different and moisture volume changes are and stretch as building components weathering capabilities, with concave, related to the height of the wall as- shrink or expand. sembly, their cumulative effect can be rodded, or v-shaped joints providing Spacing of vertical expansion joints is significant, particularly over tall sec- the best durability and water penetra- determined by considering anticipated tions of veneer. tion resistance. Struck, raked, beaded, wall movement, size of the joint, and or extruded tooling profiles should Just as brick expands over time, con- compressibility of the joint materials. be used with caution, as they tend to crete tends to shrink. As a composite Typically, expansion joints are placed provide poor weather protection and wall system that often incorporates near corners, where stress may be degrade more quickly. both of these materials, a brick ma- greatest, as well as at or near window Code Requirements sonry cavity wall must accommodate and door openings, as appropriate. these tendencies. Typically, provision for The detailing and structural de- movement is achieved through hori- Coursing and Dimensions sign of masonry is dictated by the zontal and vertical expansion joints The appearance of brick masonry governing building code, which

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Periodic Inspection and Maintenance for Brick Masonry Walls

If properly designed and constructed, brick masonry can be highly durable and tends to demand little in the way of routine repairs. However, it is still important to conduct regular inspection of the building facade to identify emerging problems and to plan for replacement of materials approaching the end of their lifespan. While the brick units used in the wall assembly may last upwards of a century, sills, parapets, chimneys, copings, and Before approving a cleaning approach, test all materials other elements with more severe weather exposure may and methods thoroughly. have a significantly shorter service life. Mortar joints may last more than 25 years before needing repairs, whereas Repair sealants and plastic flashings may need replacement in as few as five years. Mortar Joint Repointing: Repointing is the process of removing damaged or deteriorated mortar to a uniform Inspection depth and replacing it with new mortar. When mortar is To evaluate the behavior of different materials in various crumbling, cracked, or softened, repointing may be neces- weather conditions, inspect seasonally, noting potential sary to protect against water penetration. problems and needed repairs. Items to look for include: Ideally, the original mortar composition should be • Masonry: cracks, spalls, loose brick, mortar cracks, replicated. If this is not possible, a mortar with a similar or deteriorated mortar, clogged weeps, vegetative slightly lower compressive strength is recommended for growth, deteriorated sealant, efflorescence and stains, repointing. out-of-plumb units, water penetration. The existing mortar should be removed at least to a • Flashings: damage, open lap joints, stains, missing areas. depth that is twice the joint width, or until sound mortar • Caps / Copings / Sills: inadequate slope, cracks, mortar is reached. To prepare the joint, dust and debris should hairline cracks, loose or open joints, out-of-plumb be removed by brushing, blowing with air, and/or rinsing. units, missing drips. Joints should be dampened, but the brickwork should absorb surface water before new mortar is placed. Once any of the above problems have been observed, Mortar should be packed tightly in thin layers and tooled the underlying cause should be identified and corrected, to match the original profile. as well as any outward effects of the condition. Both for water penetration protection and for aesthetic Cleaning consistency, it is best to avoid partial repointing of a wall area. Cutting out and replacing all of the mortar joints Before applying a masonry cleaning product, consult the across a given wall area or distinct visual element avoids manufacturer, as the clays, additives, shales, and coatings a patchwork appearance and reduces long-term repair that compose a given brick dictate how best it should costs by replacing all of the suspect mortar in one go. be cleaned. Proprietary cleaning products formulated for brickwork may be helpful in removing stubborn stains. Sealant Replacement: Although most of the joints in Pressure washers, which may be used for wetting and a brick masonry cavity wall are filled with mortar, the rinsing, can cause irreparable damage if used at excessive intersections between brickwork and other materials, pressures to apply chemicals; the lowest pressure should such as windows, doors, roofs, or expansion joints, are be used to achieve the desired result. Improper acid filled with sealant. Since the lifespan of sealants can range cleaning procedures, including insufficient wetting/rinsing from five to twenty years, sealant deterioration is a com- and strong acid concentrations, may inadvertently lead mon source of moisture intrusion. When inspecting the to staining, etching, and increased moisture penetration. facade, look for sealant that is missing, deteriorated, torn,

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(continued from page 3) often references “ACI 530 - Building or sagging and arrange for replacement with a sealant that is compatible with Code Requirements for Masonry the adjacent materials. Structures,” a consensus standard Vegetation Removal: Ivy may look fetching along the side of a building, but the from the American Concrete Institute ivy shoots penetrate voids in the mortar and tend to contribute to water in- (ACI), the American Society of Civil filtration. Rather than pull the vines from the wall, which can damage masonry, Engineers (ASCE), and The Masonry vines should be cut and allowed to dry up; they may then be removed using Society (TMS). In addition to the a stiff fiber brush and water. If the vines have damaged the mortar, repointing standards set forth in these codes, may be necessary. technical publications from the Brick Industry Association (known as “Tech Weep Hole Repair: Clogged weep holes may be opened by means of a Notes”), are typically used when dowel or stiff wire. If weep spacing is insufficient to effectively drain moisture designing and detailing masonry to the exterior, new weep holes may need to be drilled. Consult a design structures. professional before probing or drilling, as incorrectly placed weep holes may do more harm than good, and it is easy to accidentally damage concealed Building codes and standards include underlying flashing. prescriptive requirements for the at- tachment of the veneer to a variety of Brick Unit Replacement: Severely spalled or damaged brick should be replaced back-up materials, such as wood, metal with units selected to match the originals in color, dimensions, and texture. framing, or CMU. Wind and seismic After the damaged brick has been removed from the wall, all of the existing design requirements for each type of mortar should be cleared away and the surface cleaned and prepared. With construction are typically based on the appropriate surfaces buttered with new mortar, replacement brick should “ASCE 7: Minimum Design Loads for be pressed into position and joints fully pointed and tooled. As with repoint- Buildings and Other Structures” or ing, mortar for brick replacement should be selected to match the existing on the governing building code, which mortar in properties and appearance. often references ASCE 7. Flashing Installation: When an investigation reveals that flashing is missing, damaged, or improperly installed, the exterior brick veneer must be removed to install the appropriate flashing. If the problem is allowed to persist, water will continue to become trapped in the wall cavity, leading to deterioration of the assembly and, eventually, infiltration into the building interior. Wall Tie and Anchor Retrofit: Without proper support, the exterior veneer of a cavity wall assembly is vulnerable to catastrophic collapse and failure, as it requires anchorage to the back-up to remain stable. When a wall has been constructed with insufficient ties, or where the existing connections have failed, retrofit anchors, such as helical screws, may be installed through a mor- Lateral displacement of brick veneer. tar joint and attached to the back-up substrate. Since each situation and wall assembly is different, and products vary in installation methods and limitations, Common Problems and Their it is critical to consult with a design professional and with the retrofit anchor manufacturer before attempting to repair anchorage issues. Causes Like all building assemblies, brick ma- A Note on Water-Repellent Coatings sonry is not without issues inherent Properly designed and constructed masonry walls provide water infiltration to the material, the type of construc- protection without the aid of water-repellent coatings, and, in most cases, tion, and shortcomings in the design the addition of such a product causes more problems than it solves. Water- and construction of the wall assembly. repellent coatings are no replacement for design details that resist water Astute observation of the early warn- penetration. However, there may be isolated instances in which a breathable ing signs of masonry distress enables coating can be used successfully, such as for masonry subject to extreme ex- prompt remediation of the problem, posure. A design professional can work with the manufacturer to determine which often provides a cost savings when and where a vapor-permeable water repellent product might merit over the long term, as emerging prob- consideration. lems are best addressed well before they become emergencies.

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Corrosion of steel shelf angle. Mortar joint failure. Efflorescence. Insufficient expansion joint width.

Of all issues with brick masonry con- causes of excess water infiltration in degradation or drooling, in which heat struction, those resulting from water masonry structures include mortar and ultraviolet radiation cause rubber- penetration are the most common. profiles that trap water and direct it ized flashing to soften and exude from Efflorescence into the veneer, poor flashing details the joint. around openings or penetrations that Restricted Movement Observable as white stains or salty allow moisture into the wall system, streaks on the surface of masonry and roof leaks that travel down into When expansion joints are too nar- walls, efflorescence occurs when the wall assembly. row or spaced too far apart, there is moisture within the wall assembly insufficient accommodation for brick leaches water-soluble salts from the Condensation expansion, forcing sealant out of the mortar or masonry. The main cause In some climates and conditions, dif- joint and eventually leading to cracks of efflorescence is water infiltration, ferences in humidity and air pressure and failure of the surrounding mason- whether from poor mortar joints, between inside and outside can drive ry. Failure to include expansion joints cracked brick, or other sources. Also, water vapor into the wall, where it at building corners is a common cause sloppy workmanship can clog the wall may condense and lead to moisture- of distress; as the masonry expands cavity with excess mortar and prevent related problems. Design provisions to along the plane of the wall, the brick water from reaching flashings and exit- reduce air infiltration, vapor perme- on each side of the corner comes ing the wall. Forced to find another ability, and thermal bridging can help together, leading to long vertical cracks means of escape, trapped moisture to control condensation. and/or brick displacement at building travels through the brick, resulting in Flashing Problems corners. efflorescence. Flashing detailing is particularly im- Structural Issues Once the problem has been identi- portant at intersections and ter- Causes of structural distress in brick fied and remediated, it may be difficult minations. Where the segments of masonry cavity walls are often related or even impossible to clean away continuous flashing intersect, they to the corrosion of embedded steel salt deposits that have bonded to should be lapped and sealed using a elements, which can lead to cracks and the masonry surface. If moisture has method appropriate to the material. displacement. As water penetration reached the building interior, water Discontinuous flashing, as at a win- causes steel lintels, reinforcement, an- damage and mold may also need to dow or door opening, should extend chors, ties, and accessories to corrode, be addressed. beyond the end of the lintel, with the they expand, exerting tremendous Freeze-Thaw Damage ends turned up to prevent water from pressure on the surrounding facade, In temperate climates, water that running back into the wall from the which can sometimes fail dramatically penetrates masonry walls may lead edge of the flashing. as a result. to structural damage, as low tem- Plastics, composites, and thin metal Insufficient or failed anchorage of the peratures cause trapped moisture to cannot be formed into a drip edge. veneer to the back-up can lead to freeze and expand, applying pressure Instead, these materials should be ter- bowing and/or lateral displacement of to the surrounding materials. Typical minated within the veneer to prevent the masonry.

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Brick Masonry Cavity Walls Schering Plough Headquarters Summit, New Jersey To develop long-lasting rehabilitation Facade Reconstruction solutions for brick masonry wall sys- tems, our design professionals evalu- Albright College ate existing conditions and identify Gingrich Library underlying causes of deterioration and Reading, Pennsylvania failure. Through engineering analysis, Building Envelope Investigation evidence-based empirical design, and Stamford Corners detail-oriented project administration, Stamford, Connecticut Hoffmann Architects applies nearly 40 Facade Rehabilitation years of professional practice to the Yonkers Employment Center and prevention and resolution of masonry Westchester Department of Health distress. 20 South Broadway Hoffmann Architects’ recent projects Yonkers, New York involving investigation and remediation Masonry Exterior Wall Investigation of brick masonry facades include: Edge Fund Advisors, 4 New York Plaza in The Ellington Apartments New York, New York. Facade Investigation and Rehabilitation. Southern Connecticut State Washington, District of Columbia University, Residence Halls Facade Investigation and Repair New Haven, Connecticut Fairfield Warde High School Barnard College Masonry Condition Survey and Leak Fairfield, Connecticut Plimpton Hall Investigation Facade Investigation and Repair New York, New York Facade Investigation and Repair Episcopal High School State University of New York Stewart Student Center Farmingdale State College Saint Joseph Church Alexandria, Virginia Whitman Hall Poquonock, Connecticut Masonry Facade Consultation Farmingdale, New York Facade Investigation and Repair Princeton University Building Envelope Rehabilitation The Sheffield Lawrence Apartments New York, New York Princeton, New Jersey Building Envelope Consultation and Building Envelope Study and Repair Repair Aetna Headquarters ARINC Headquarters Rogers Building Annapolis, Maryland Hartford, Connecticut Brick Displacement and Leak Masonry Investigation and Repair Remediation Verizon, 95 William Street Roberto Clemente and Riverbank Newark, New Jersey Chase Collegiate School, Saint Margaret’s State Parks Facade Investigation, Repair, and Hall in Waterbury, Connecticut. Portico and New York, New York Replacement Masonry Rehabilitation. Masonry Facade Consultation

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Hoffmann Architects, Inc. 2321 Whitney Avenue Hamden, CT 06518

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(continued from page 6) cavity walls are ubiquitous across all building styles and types. JOURNAL is a publication of Hoffmann Although cavity walls did not Architects, Inc., specialists in the even feature in building codes rehabilitation of building exteriors. The firm’s work focuses on existing struc- until at least the late 1930s, the tures, diagnosing and resolving prob- extensive testing, research, and lems within roofs, facades, windows, field performance data that waterproofing materials, structural sys- have emerged since then have tems, plazas/terraces, parking garages, and historic and landmark structures. refined brick cavity walls to the We also provide consulting services for degree that the Brick Industry new building construction, as well as Association calls them “the pre- litigation and claim support. Sealant alone cannot resolve masonry distress. mier masonry wall system.” For address changes, free subscriptions, Like all building assemblies, even or information on the topics discussed Readily identifiable by their tapering the dependable masonry cavity wall in this issue, contact our Marketing shape, deflection cracks may occur at can succumb to leaks, cracks, stains, Department at 800-239-6665, [email protected], or: steel shelf angles attached to spandrel and deterioration if not correctly de- beams that deflect. Uneven settlement signed, built, and maintained. To treat 2321 Whitney Avenue in the foundation due to unstable soil persistent problems, and, better, to Hamden, CT 06518 conditions may also be the cause of prevent new ones from emerging, it 203-239-6660 stress cracking in masonry walls, as is important to understand the basics one portion of the structure settles 1040 Avenue of the Americas, Ste. 14C of brick cavity wall construction and New York, NY 10018 more than another. to recognize the symptoms of distress 212-789-9915 and failure. By proactively addressing Addressing the Challenges of 2611 Jefferson Davis Highway, Ste. 200 incipient design, detailing, workman- Modern Masonry Facades Arlington, VA 22202 ship, and age-related problems, build- 703-253-9800 Popular for their superior resistance ing owners and managers can prolong to rain penetration, sound transmis- the life of the building and avoid the www.hoffarch.com sion, fire, and heat transfer—and for expense and disruption of major Editor/Production: Alison Hoffmann their cost-effectiveness—masonry rehabilitation.

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