ISSUE 3/2003 VOLUME 21 NUMBER 3

Journal of architectural technology published by Hoffmann Architects, specialists in the rehabilitation of building exteriors. Exterior Brick Masonry Walls: Causes of and Solutions to Inevitable Deterioration

Scott D. Chamberlain

T he history of brick, man’s oldest angles as drastic as 70 degrees, across manufactured building product, is long and some of China’s most severe and storied. Used in construction for mountainous terrain. thousands of years, it reflects the evolution and variety of our ever-changing As with all building envelope systems, constructed world. deterioration is inevitable. The key to sustaining brick masonry exterior walls The first bricks were made from the mud for as long as possible is preventative of riverbanks and baked in the sun, as maintenance and repair. Preventing long ago as 10,000 B.C. Chopped straw minor deterioration from escalating into and grass were added to prevent bigger problems will ensure a distortion and cracking. Around 4,000 structure’s longevity. B.C., brick manufacturers began producing uniform shapes and firing them in kilns. Form and Function Firing caused the clay particles to bond chemically, hence improving brick’s Brick masonry walls consist of uniformly durability. shaped and sized bricks that are laid in courses with mortar joints. A singular Brick’s aesthetic appeal and diversity is vertical section of brick masonry, one undeniable. From the historic red unit in thickness, is referred to as a schoolhouses that dot the countryside to wythe. Bricks can be of various colors the landmarked clad in and hardnesses. They may be glazed, glazed brick, from Thomas Jefferson’s pressed or molded, or customized to Monticello to the low-rise buildings of suit the design requirements for a contemporary suburban office parks, brick particular structure. is represented in an astounding array of

> The landmarked Chrysler Building in New architectural styles. Bricks need to conform to a number of York City is clad in glazed brick. Though the criteria in order to be effective building towering structure is perhaps best known for its Aside from its visual appeal, brick has blocks. They should be durable and shining spire, its facade features intricate, great longevity. It withstands the tests of meet the required minimum automobile-inspired brick patterns. time and Mother Nature. Take, for compressive strength dictated by the example, The Great Wall of China. Its design. They should not exceed construction began in 221 B.C., and it still maximum water absorption and stands strong today, even where it leans at saturation guidelines, should pass

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Scott D. Chamberlain, Project Manager, oversees a variety of building envelope rehabilitation projects, including those for brick masonry facades, for Hoffmann Architects. JOURNAL

Figure 1 Types of Brick Masonry Walls

Single Multiple Reinforced Composite wythe wythe brick masonry CMU and brick Cavity (barrier) (barrier) (barrier) (barrier) (drainage)

(continued from page 1) understanding of the means by which successful at preventing water freezing and thawing tests, and should water infiltrates a wall system; the infiltration as drainage or multiple wythe meet the weathering challenges of a proper construction of a selected wall barrier walls. region. system and its suitability for a structure’s particular climate; the Multiple wythe brick barrier walls that For example, a brick specified for a appropriate use of various types of are three wythes or more are designed structure in hot, dry southwestern New specified materials, such as brick and to prevent water infiltration through Mexico would likely fail in New England mortar; and, methods for expelling mass. While not always successful, the and other northern climates where moisture that has entered a wall, by amount of water that the wall is buildings are subjected to a wide range of means of flashing and weep systems. allowed to absorb over a period of climatic conditions, including freeze-thaw time should be less than can be cycling. Types of wall construction dissipated in the same period, keeping water from reaching the interior surface Waterproofing for Brick Masonry In terms of waterproofing, exterior of the wall. Exterior Walls brick masonry walls can be classified as either barrier or drainage walls. Narrower multiple wythe barrier walls The primary role of the building and composite walls depend on a envelope is to separate and protect an Barrier walls collar joint to provide a barrier within interior space created by man from the the wall. The collar joint, grouted solid natural environment. First and More common prior to the with mortar, is the joint between the foremost, it holds the forces of Mother development of cavity walls, barrier exterior wythe of masonry and the Nature at bay by sealing a building walls are constructed of solid masonry backup masonry. The collar joint blocks from the elements: wind, rain, snow, ice, without the use of a drainage cavity. water that penetrates the face of a thermal conditions (heat/cold). They may be constructed of multiple wall. That water then either follows the wythes of brick, or they may be collar joint down to the flashing level Water is a constant threat to the composite walls constructed of brick where it is expelled through the bed building envelope’s ability to protect masonry combined with a variety of joint and/or weep holes, or it dissipates interior space; it is a principle cause of masonry materials such as Concrete out through the face of the wall. deterioration in building envelope Masonry Units (CMUs) or terra cotta systems, and it is no different in brick block. Barrier walls may also be load- Drainage walls masonry exterior walls. It is therefore bearing walls reinforced with steel to critical that, in addition to the support or help support a structure. Drainage walls are designed with a requirements of structural design, an Single wythe barrier walls are generally cavity within the wall. The cavity is exterior brick masonry wall be constructed from a masonry unit that located between the outer wythe of designed to resist water infiltration to is wider (deeper) than a standard unit brick masonry and the back-up the highest degree possible. making the wall more impervious to material that may consist of brick, Successful waterproofing of exterior water penetration. However, single CMUs, metal or wood stud framing. brick masonry walls relies upon a clear wythe barrier walls are often not as

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Like the collar joint in a barrier wall, the cavity is designed to stop the The Roles of Relieving (Shelf) Angles and Soft Joints penetration of water that enters the Building components expand and face of a wall from traveling to the contract with changes in temperature interior, backup portion of a wall. and moisture content. Relieving (or However, instead of forming a shelf) angles are necessary to physical barrier, the cavity forms a accommodate this movement in break that water has difficulty masonry walls. If a relieving angle is crossing. When water penetrates the omitted, cracks will develop where the face brick, it runs down the interior brick is restrained as the brick grows and surface of the exterior wythe of brick the backup shrinks. to the flashing level where it is Soft joints should be constructed at expelled through the bed joint and/or relieving angles to create relief for weep holes. brick’s expansion. If soft joints at relieving angles are not properly In order for drainage walls to be constructed, the brick will be crushed > What happens when relieving effective, careful consideration must and water will be allowed into the wall angles are omitted? Cracking. Here, be given to design details for system. Control and expansion joints brick has expanded; the backup has flashings prior to construction. are needed vertically as well. Without shrunk; and, cracks have developed Improperly installed flashings will fail. expansion control, brick will slide off of where the brick is restrained at the relieving angle. balconies, windows and vents. Furthermore, the cavity must be kept clean and free of debris both during generally easily detected by visual and after construction, as mortar inspection. Symptoms include: droppings and other construction debris in the cavity may clog weep · staining and efflorescence; holes. Mortar, debris, and improperly designed brick ties may also bridge · cracking; the cavity, allowing water to penetrate the backup above the level of the · spalling; waterproofing.

· deteriorated mortar joints; > These mortar joints appear to be properly Symptoms and Causes of tooled, yet there is a lack of adhesion between the Deterioration in Brick Masonry Wall · loose, displaced or crushed brick; mortar and the brick. The cause? Either the mortar Construction had begun to set too early or the brick was very · mildew, a fungus; and, dry at the time of repointing. A repointing project is The symptoms of deterioration in only as good as its weakest component. brick masonry wall construction are (continued on page 4)

> Below left, cracking through brick masonry wall. Below middle, eroded mortar joints below this cornice . Below right, inadequate partial repointing has left many mortar joints vulnerable to water intrusion.

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(continued from page 3) · vegetative growth, such as moss in The usual suspects: failed or directly above all areas of flashing. mortar joints. inadequate flashing and weep systems Installing weeps too far above flashing is a mistake, as water may collect Mortar deterioration A key component in both drainage and beneath the weeps and back up at the barrier wall systems, flashing is an flashing. Mortar is as integral to brick masonry impermeable membrane that forms a wall construction as bricks themselves. horizontal barrier that stops the vertical A flashing and weep system is an Mortar holds a masonry wall together movement of water and directs it out of integral part of an exterior brick masonry and serves as a barrier against the a wall system. wall system and key to expelling water passage of air and water. Some from within a wall. However, unless common causes of mortar Weep holes provide a direct route for properly installed and maintained, deterioration include improperly tooled water to exit a wall. In order to be flashing and weeps can be a cause of joints; water infiltration that washes effective, weep holes should be located water infiltration and damage to a wall. away mortar’s soluble salts, reducing its impermeability; and, the eroding force of wind and rain. When Flashing and Weep Systems Fail...

Loss of mortar leaves an exterior wall Counter-clockwise from left: vulnerable to water infiltration. Leaks in the flashing at this window Repointing is required when the bond lead not only to water infiltration into between the mortar and the brick is the building, but also to corrosion of broken, when mortar has crumbled steel lintels and deterioration of the from the joint, when hairline cracks anchorage system that supports the appear in the mortar, and when brick face. mortar has eroded to expose the Efflorescence at brick masonry back-up wall material. under cornices and belt courses is a sure sign of water infiltration through Efflorescence leaking flashing or open butt joints in the stones above. Efflorescence occurs when water washes soluble salts out of mortar and The bed joints above the through- onto the surface of brick. White stains wall flashing at the base of this wall have and/or build-up of white, crystalline been sealed over, trapping moisture structures develop on brick surfaces as within the wall, causing spalling of brick. the water evaporates. The bed joints above the through- Cracking and spalling wall flashing have been sealed over at this parapet, causing water Expansion from thermal changes, from retention. Note moss growth and water absorption and from freezing efflorescence. and thawing of retained moisture causes cracking and spalling (the breaking off of the face of brick) in brick masonry walls. The corrosion of embedded steel reinforcing in masonry walls may also lead to cracking and spalling of brick.

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In a drainage or barrier wall system, * flashings are typically located where Figure 2 Masonry Facade Inspection Checklist intersecting elements have inter- FFeacade rupted the cavity or collar joint AAarea CCnondition within a wall. These locations A B C D include continuous relieving angles; wall openings such as windows or Deteriorated mortar joints louvers; and continuous horizontal Cracked bricks elements like stone or concrete cornices, belt courses, and water Efflorescence tables. Leaks in the flashings at these locations can lead not only to Loose bricks water penetration into the building, but also to corrosion of the steel Missing/clogged weep holes lintels and deterioration of the Vegetative growth anchorage systems that support the brick façade or masonry MMsasonry Walls Deteriorated sealant joints appurtenances. Corrosion of steel lintels is often indicated by spalling Structural deterioration of brick at the jamb of the opening just below the lintel, loss of mortar Failing expansion joints around the embedded steel, or Surface spalling rust staining on the face of the brick. Stains

Efflorescence at brick masonry under Water penetration cornices and belt courses is a sure sign of water infiltration through leak- Vertical cracks at building corners ing flashing or open butt joints in the Deteriorated sealant joints stones above. Water washes the soluble salts out of the mortar onto Rusting/sagging lintels the surface of the brick where it crys- WsWindows tallizes through evaporation of the Cracked/spalled sills water, forming what appears to be white fuzz on the surface of the brick. Deteriorated mullions The loss of soluble salts eventually Damaged parapet copings affects the permeability of the mor- PsParapets tar allowing water to permeate the Deteriorated parapet walls joints, which can cause further dete- rioration of the mortar and brick. Bent flashing

Through-wall flashings are also F/Flashing/ Missing flashing typically found in roof parapets and CCgounterflashing Open lap joints at the base of walls where they extend out of the wall to form Stains counterflashings over the termina- tion of a roofing system. These Cracks systems are often mistaken for CCsaps/Copings Loose or open joints (continued on page 6) Displacement

* Periodic inspections are key to making timely and appropriate repairs. This list indicates what to look for during inspections.

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The Goodwin Hotel’s Award-Winning Facade Restoration

T he Queen Anne style Goodwin Following completion of the hotel, reconstruction of the upper exterior Hotel in Hartford, symptoms of masonry distress— walls and roof of the structure. These was originally designed as an spalling, cracking, efflorescence— repairs included the replacement and/or apartment building in the late became apparent at the structure’s restoration of damaged brick and 1800s by architects original exterior walls and remained ornamental terra cotta, complete Kimball and Wise. Constructed persistent after initial repair and repointing of all mortar joints and the using masonry bearing walls, the restoration efforts. The owner called application of a water-repellant coating. structure’s exterior façades were upon Hoffmann Architects to accentuated with ornamental investigate the causes of this deterio- Though faced with significant brickwork and terra cotta. During ration and to develop a program to challenges—the customization of 14 the late 1980s, the interior of the restore the exterior of the building. replacement brick shapes, the task of building was demolished, leaving repointing narrow mortar joints, and the the exterior walls for incorpora- The firm’s comprehensive restoration careful phasing of work to accommo- tion into a new hotel facility. program consisted of the complete date not less than 80% occupancy of the hotel’s guest rooms at any time—

> the firm designed a restoration program The Goodwin Hotel Hartford, Connecticut. The hotel after Hoffmann Architects’ that has provided the owner with a award-winning restoration. watertight building envelope while successfully maintaining the aesthetic and historic features of the Goodwin Hotel’s original design.

> Severely deteriorated brick at the hotel necessitated complete reconstruction of the upper exterior walls and replacement of face brick at lower areas.

(continued from page 5) consequently causing further qualified design professional will be reglet-mounted counterflashings, the deterioration. able to recommend rehabilitative sole purpose of which is to provide action to prevent these symptoms protection for the roof flashings. Bed The Solutions from developing into more severe, joints above properly installed more costly, building envelope failures. through-wall flashings normally consist Periodic inspections and routine of mortar, with or without weeps, and maintenance During inspections, it should be kept in allow water to filter out of the wall. mind that water is most likely to Bed joints that also serve as sealant Periodic inspections are necessary in penetrate brick masonry walls through: joints require a weep system to order to make timely and appropriate allow water to exit the wall. repairs to areas of deterioration at brick · failed mortar joints; Frequently, these joints are mistakenly masonry walls. The Masonry Facade viewed as a source of water Inspection Checklist on page 5 provides · parapets and copings; infiltration and are sealed over, indicators of deterioration to look for trapping moisture within a wall and when conducting an inspection. A (continued on page 8)

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Brick Masonry Rehabilitation University of Maryland School of Medicine Eastern Shore Sterling Hall of Medicine The following representative projects Student Development Center New Haven, Connecticut included brick masonry rehabilitation. Princess Anne, Maryland Building Envelope Rehabilitation Facade Rehabilitation Chrysler Building Scholastic Publishing New York New York 25 Sigourney Street New York, New York Spire and Facade Restoration Hartford, Connecticut Building Envelope Rehabilitation Building Envelope Survey and 555 Broadway JP Morgan Chase and Co... Rehabilitation New York, New York Pfizer,,, Inc... Building Envelope Survey and Facade The Smithsonian Institution Global Manufacturing Facility Restoration The Renwick Gallery Brooklyn, New York 15 Broad Street Washington, District of Columbia Building Envelope Rehabilitation 37 Wall Street Water Infiltration Remediation 43 Exchange Place 1000 Thomas Jefferson Street, NW Columbia University Washington, District of Columbia The Goodwin Hotel 44 Morningside Drive Facade Rehabilitation Hartford, Connecticut New York, New York Facade and Roof Restoration Building Envelope Rehabilitation Capital Community College (Historic G. Fox Building) Columbia University IBM Corporation Hartford, Connecticut Hammer Health Science Center Southbury, Connecticut Facade and Roof Rehabilitation New York, New York Building Envelope Rehabilitation Facade Investigation and Rehabilitation University of Connecticut New York City School Construction Dodd Archives Research Center Authority Storrs, Connecticut Long Island City, New York Building Envelope Rehabilitation Exterior Building Maintenance Manuals and Facade Rehabilitation The George Washington University Stuart Hall Congregational Church Washington, District of Columbia United Church of Christ Facade Rehabilitation Naugatuck, Connecticut Steeple and Parish House Verizon Communications

Rehabilitation New York, New York > IBM Corporation Advanced Business Local Law 11 Repairs and Building Institute Palisades, New York. Hoffmann Fairfield Public Schools Envelope Rehabilitation Architects’ project work included masonry Fairfield, Connecticut Multiple Buildings in Brooklyn rehabilitation of facades at this corporate Building Envelope Rehabilitation and Manhattan training facility.

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Repointing Deteriorated Mortar JJJ oints JOURNAL is a publication of Hoffmann Architects, specialists in the The most common and inevitable brick Figure 3 rehabilitation of building exteriors. masonry problem is deteriorated The firm’s work includes investigative and Concave/rodded mortar joints. Proper repointing of rehabilitative architecture/engineering mortar joints requires: tooling of mortar joints is recommended services for the analysis and resolution of problems within · careful removal of deteriorated, as the most effective roofs, facades, glazing, and structural inappropriate or loose mortar; tooling for preventing water infiltration. systems of existing buildings, plazas/ terraces, and parking garages. · cleaning the joints of old mortar and dirt; and, fills them completely. Ideally, they will be Please send news, technical information, tooled to achieve a concave (or address changes, or requests for free · installation of an appropriate— rodded) surface that is optimal for subscriptions to Editor, Hoffmann flexible, yet durable—mortar. directing water off of a brick face (See Architects JOURNAL, 432 Washington Figure 3). Improper tooling allows water Avenue, North Haven, Connecticut During mortar installation, proper to rest in joints, threatening to enter 06473. For answers to specific questions tooling of joints will ensure that mortar masonry walls. or for information on the services Hoffmann Architects offers, please contact (continued from page 6) Conclusion Sandra Matheny at (203) 239-6660. · sills, cornices and belt courses; 432 Washington Avenue Exterior brick masonry walls are durable, North Haven CT 06473 · areas of failed/inadequate flashing; but they are susceptible to inevitable 203 239-6660 and, deterioration, as are all building envelope 500 Fifth Avenue, Suite 830 systems. Understanding and resolving New York NY 10110 · failed sealant joints. the root causes of deterioration is critical 212 789-9915 to the development of lasting 1001 Connecticut Avenue NW, Suite 825 In addition to periodic inspections, rehabilitation solutions. Routine Washington DC 20036 routine maintenance plays an inspections and preventative maintenance 202 530-1100 important role in the longevity of and repairs are crucial in promoting the exterior brick masonry walls. Not only longevity of these facades. By inspecting For more information on the should cavities be kept clean and free walls on a routine basis, areas of minor topics discussed in this article, of debris during and after construction, deterioration can be detected and visit us on the web at facades should be kept clean of repaired before they escalate into more www.hoffmannarchitects.com, pollutants and free of vegetation, such severe, and more costly, problems. or contact us at as vine growth, which can penetrate [email protected]. the masonry, facilitating water Editor & Graphic Services: infiltration. Maryellen Apelquist

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