Scott D. Chamberlain

Journal of architectural

technology published

by Hoffmann Architects,

specialists in the rehabilitation

of building exteriors.

I S S U E 3 / 2 0 0 3 � V O L U M E 21 � N U M B E R 3

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Exterior Brick Masonry Walls:Causes of and Solutions to Inevitable Deterioration

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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.

The landmarked Chrysler Building in NewYork City is clad in glazed brick. Though thetowering structure is perhaps best known for itsshining spire, its facade features intricate,automobile-inspired brick patterns.

he history of brick, man’s oldestmanufactured building product, is long andstoried. Used in construction forthousands of years, it reflects the evolutionand variety of our ever-changingconstructed world.

The first bricks were made from the mudof riverbanks and baked in the sun, aslong ago as 10,000 B.C. Chopped strawand grass were added to preventdistortion and cracking. Around 4,000B.C., brick manufacturers began producinguniform shapes and firing them in kilns.Firing caused the clay particles to bondchemically, hence improving brick’sdurability.

Brick’s aesthetic appeal and diversity isundeniable. From the historic redschoolhouses that dot the countryside tothe landmarked Chrysler Building clad inglazed brick, from Thomas Jefferson’sMonticello to the low-rise buildings ofcontemporary suburban office parks, brickis represented in an astounding array ofarchitectural styles.

Aside from its visual appeal, brick hasgreat longevity. It withstands the tests oftime and Mother Nature. Take, forexample, The Great Wall of China. Itsconstruction began in 221 B.C., and it stillstands strong today, even where it leans at

angles as drastic as 70 degrees, acrosssome of China’s most severe andmountainous terrain.

As with all building envelope systems,deterioration is inevitable. The key tosustaining brick masonry exterior wallsfor as long as possible is preventativemaintenance and repair. Preventingminor deterioration from escalating intobigger problems will ensure astructure’s longevity.

Form and Function

Brick masonry walls consist of uniformlyshaped and sized bricks that are laid incourses with mortar joints. A singularvertical section of brick masonry, oneunit in thickness, is referred to as awythe. Bricks can be of various colorsand hardnesses. They may be glazed,pressed or molded, or customized tosuit the design requirements for aparticular structure.

Bricks need to conform to a number ofcriteria in order to be effective buildingblocks. They should be durable andmeet the required minimumcompressive strength dictated by thedesign. They should not exceedmaximum water absorption andsaturation guidelines, should pass

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freezing and thawing tests, and shouldmeet the weathering challenges of aregion.

For example, a brick specified for astructure in hot, dry southwestern NewMexico would likely fail in New Englandand other northern climates wherebuildings are subjected to a wide range ofclimatic conditions, including freeze-thawcycling.

Waterproofing for Brick MasonryExterior Walls

The primary role of the buildingenvelope is to separate and protect aninterior space created by man from thenatural environment. First andforemost, it holds the forces of MotherNature at bay by sealing a buildingfrom the elements: wind, rain, snow, ice,thermal conditions (heat/cold).

Water is a constant threat to thebuilding envelope’s ability to protectinterior space; it is a principle cause ofdeterioration in building envelopesystems, and it is no different in brickmasonry exterior walls. It is thereforecritical that, in addition to therequirements of structural design, anexterior brick masonry wall bedesigned to resist water infiltration tothe highest degree possible.Successful waterproofing of exteriorbrick masonry walls relies upon a clear

understanding of the means by whichwater infiltrates a wall system; theproper construction of a selected wallsystem and its suitability for astructure’s particular climate; theappropriate use of various types ofspecified materials, such as brick andmortar ; and, methods for expellingmoisture that has entered a wall, bymeans of flashing and weep systems.

TTTTTypes of wall constrypes of wall constrypes of wall constrypes of wall constrypes of wall constructionuctionuctionuctionuction

In terms of waterproofing, exteriorbrick masonry walls can be classifiedas either barrier or drainage walls.

Barrier walls

More common prior to thedevelopment of cavity walls, barrierwalls are constructed of solid masonrywithout the use of a drainage cavity.They may be constructed of multiplewythes of brick, or they may becomposite walls constructed of brickmasonry combined with a variety ofmasonry materials such as ConcreteMasonry Units (CMUs) or terra cottablock. Barrier walls may also be load-bearing walls reinforced with steel tosupport or help support a structure.Single wythe barrier walls are generallyconstructed from a masonry unit thatis wider (deeper) than a standard unitmaking the wall more impervious towater penetration. However, singlewythe barrier walls are often not as

successful at preventing waterinfiltration as drainage or multiple wythebarrier walls.

Multiple wythe brick barrier walls thatare three wythes or more are designedto prevent water infiltration throughmass. While not always successful, theamount of water that the wall isallowed to absorb over a period oftime should be less than can bedissipated in the same period, keepingwater from reaching the interior surfaceof the wall.

Narrower multiple wythe barrier wallsand composite walls depend on acollar joint to provide a barrier withinthe wall. The collar joint, grouted solidwith mortar, is the joint between theexterior wythe of masonry and thebackup masonry. The collar joint blockswater that penetrates the face of awall. That water then either follows thecollar joint down to the flashing levelwhere it is expelled through the bedjoint and/or weep holes, or it dissipatesout through the face of the wall.

Drainage walls

Drainage walls are designed with acavity within the wall. The cavity islocated between the outer wythe ofbrick masonry and the back-upmaterial that may consist of brick,CMUs, metal or wood stud framing.

Figure 1 Types of Brick Masonry Walls

SingleSingleSingleSingleSinglewythewythewythewythewythe

(barrier)(barrier)(barrier)(barrier)(barrier)

MultipleMultipleMultipleMultipleMultiplewythewythewythewythewythe

(barrier)(barrier)(barrier)(barrier)(barrier)

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(drainage)(drainage)(drainage)(drainage)(drainage)

CompositeCompositeCompositeCompositeCompositeCMU and brickCMU and brickCMU and brickCMU and brickCMU and brick

(barrier)(barrier)(barrier)(barrier)(barrier)

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

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Like the collar joint in a barrier wall,the cavity is designed to stop thepenetration of water that enters theface of a wall from traveling to theinterior, backup portion of a wall.However, instead of forming aphysical barrier, the cavity forms abreak that water has difficultycrossing. When water penetrates theface brick, it runs down the interiorsurface of the exterior wythe of brickto the flashing level where it isexpelled through the bed joint and/orweep holes.

In order for drainage walls to beeffective, careful consideration mustbe given to design details forflashings prior to construction.Improperly installed flashings will fail.

Furthermore, the cavity must be keptclean and free of debris both duringand after construction, as mortardroppings and other constructiondebris in the cavity may clog weepholes. Mortar, debris, and improperlydesigned brick ties may also bridgethe cavity, allowing water to penetratethe backup above the level of thewaterproofing.

Symptoms and Causes ofDeterioration in Brick Masonry WallConstruction

The symptoms of deterioration inbrick masonry wall construction are

These mortar joints appear to be properlytooled, yet there is a lack of adhesion between themortar and the brick. The cause? Either the mortarhad begun to set too early or the brick was verydry at the time of repointing. A repointing project isonly as good as its weakest component.

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What happens when relievingangles are omitted? Cracking. Here,brick has expanded; the backup hasshrunk; and, cracks have developedwhere the brick is restrained atbalconies, windows and vents.

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Building components expand andcontract with changes in temperatureand moisture content. Relieving (orshelf) angles are necessary toaccommodate this movement inmasonry walls. If a relieving angle isomitted, cracks will develop where thebrick is restrained as the brick grows andthe backup shrinks.

Soft joints should be constructed atrelieving angles to create relief forbrick’s expansion. If soft joints atrelieving angles are not properlyconstructed, the brick will be crushedand water will be allowed into the wallsystem. Control and expansion jointsare needed vertically as well. Withoutexpansion control, brick will slide off ofthe relieving angle.

The Roles of Relieving (Shelf) Angles and Soft Joints

generally easily detected by visualinspection. Symptoms include:

· staining and efflorescence;

· cracking;

· spalling;

· deteriorated mortar joints;

· loose, displaced or crushed brick;

· mildew, a fungus; and,

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· vegetative growth, such as moss inmortar joints.

MorMorMorMorMortar detertar detertar detertar detertar deteriorioriorioriorationationationationation

Mortar is as integral to brick masonrywall construction as bricks themselves.Mortar holds a masonry wall togetherand serves as a barrier against thepassage of air and water. Somecommon causes of mortardeterioration include improperly tooledjoints; water infiltration that washesaway mortar’s soluble salts, reducing itsimpermeability; and, the eroding forceof wind and rain.

Loss of mortar leaves an exterior wallvulnerable to water infiltration.Repointing is required when the bondbetween the mortar and the brick isbroken, when mortar has crumbledfrom the joint, when hairline cracksappear in the mortar, and whenmortar has eroded to expose theback-up wall material.

EfflorescenceEfflorescenceEfflorescenceEfflorescenceEfflorescence

Efflorescence occurs when waterwashes soluble salts out of mortar andonto the surface of brick. White stainsand/or build-up of white, crystallinestructures develop on brick surfaces asthe water evaporates.

CrackingCrackingCrackingCrackingCracking and spalling and spalling and spalling and spalling and spalling

Expansion from thermal changes, fromwater absorption and from freezingand thawing of retained moisturecauses cracking and spalling (thebreaking off of the face of brick) inbrick masonry walls. The corrosion ofembedded steel reinforcing in masonrywalls may also lead to cracking andspalling of brick.

The usual suspects: failed orThe usual suspects: failed orThe usual suspects: failed orThe usual suspects: failed orThe usual suspects: failed orinadequate flashing and weep systemsinadequate flashing and weep systemsinadequate flashing and weep systemsinadequate flashing and weep systemsinadequate flashing and weep systems

A key component in both drainage andbarrier wall systems, flashing is animpermeable membrane that forms ahorizontal barrier that stops the verticalmovement of water and directs it out ofa wall system.

Weep holes provide a direct route forwater to exit a wall. In order to beeffective, weep holes should be located

directly above all areas of flashing.Installing weeps too far above flashingis a mistake, as water may collectbeneath the weeps and back up at theflashing.

A flashing and weep system is anintegral part of an exterior brick masonrywall system and key to expelling waterfrom within a wall. However, unlessproperly installed and maintained,flashing and weeps can be a cause ofwater infiltration and damage to a wall.

When Flashing and Weep Systems Fail...

Counter-clockwise from left: Leaks in the flashing at this windowlead not only to water infiltration intothe building, but also to corrosion ofsteel lintels and deterioration of theanchorage system that supports thebrick face.

Efflorescence at brick masonryunder cornices and belt courses is asure sign of water infiltration throughleaking flashing or open butt joints in thestones above.

The bed joints above the through-wall flashing at the base of this wall havebeen sealed over, trapping moisturewithin the wall, causing spalling of brick.

The bed joints above the through-wall flashing have been sealed over atthis roof parapet, causing waterretention. Note moss growth andefflorescence.

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In a drainage or barrier wall system,flashings are typically located whereintersecting elements have inter-rupted the cavity or collar jointwithin a wall. These locationsinclude continuous relieving angles;wall openings such as windows orlouvers; and continuous horizontalelements like stone or concretecornices, belt courses, and watertables. Leaks in the flashings atthese locations can lead not only towater penetration into the building,but also to corrosion of the steellintels and deterioration of theanchorage systems that supportthe brick façade or masonryappurtenances. Corrosion of steellintels is often indicated by spallingof brick at the jamb of the openingjust below the lintel, loss of mortararound the embedded steel, orrust staining on the face of thebrick.

Efflorescence at brick masonry undercornices and belt courses is a suresign of water infiltration through leak-ing flashing or open butt joints in thestones above. Water washes thesoluble salts out of the mortar ontothe surface of the brick where it crys-tallizes through evaporation of thewater, forming what appears to bewhite fuzz on the surface of the brick.The loss of soluble salts eventuallyaffects the permeability of the mor-tar allowing water to permeate thejoints, which can cause further dete-rioration of the mortar and brick.

Through-wall flashings are alsotypically found in roof parapets andat the base of walls where theyextend out of the wall to formcounterflashings over the termina-tion of a roofing system. Thesesystems are often mistaken for

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

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he Queen Anne style GoodwinHotel in Har tford, Connecticutwas originally designed as anapar tment building in the late1800s by New York architectsKimball and Wise. Constructedusing masonry bearing walls, thestructure’s exterior façades wereaccentuated with ornamentalbrickwork and terra cotta. Duringthe late 1980s, the interior of thebuilding was demolished, leavingthe exterior walls for incorpora-tion into a new hotel facility.

Following completion of the hotel,symptoms of masonry distress—spalling, cracking, efflorescence—became apparent at the structure’soriginal exterior walls and remainedpersistent after initial repair andrestoration effor ts. The owner calledupon Hoffmann Architects toinvestigate the causes of this deterio-ration and to develop a program torestore the exterior of the building.

The firm’s comprehensive restorationprogram consisted of the complete

The Goodwin Hotel’s Award-Winning Facade Restoration

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The Goodwin Hotel Hartford, Connecticut. The hotel after Hoffmann Architects’award-winning restoration.

(continued on page 8)

reconstruction of the upper exteriorwalls and roof of the structure. Theserepairs included the replacement and/orrestoration of damaged brick andornamental terra cotta, completerepointing of all mortar joints and theapplication of a water-repellant coating.

Though faced with significantchallenges—the customization of 14replacement brick shapes, the task ofrepointing narrow mortar joints, and thecareful phasing of work to accommo-date not less than 80% occupancy ofthe hotel’s guest rooms at any time—the firm designed a restoration programthat has provided the owner with awatertight building envelope whilesuccessfully maintaining the aestheticand historic features of the GoodwinHotel’s original design.

> Severely deteriorated brick at the hotelnecessitated complete reconstruction of theupper exterior walls and replacement of facebrick at lower areas.

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reglet-mounted counterflashings, thesole purpose of which is to provideprotection for the roof flashings. Bedjoints above properly installedthrough-wall flashings normally consistof mortar, with or without weeps, andallow water to filter out of the wall.Bed joints that also serve as sealantjoints require a weep system toallow water to exit the wall.Frequently, these joints are mistakenlyviewed as a source of waterinfiltration and are sealed over,trapping moisture within a wall and

consequently causing furtherdeterioration.

The Solutions

PPPPPerererereriodic inspections and routineiodic inspections and routineiodic inspections and routineiodic inspections and routineiodic inspections and routinemaintenancemaintenancemaintenancemaintenancemaintenance

Periodic inspections are necessary inorder to make timely and appropriaterepairs to areas of deterioration at brickmasonry walls. The Masonry FacadeInspection Checklist on page 5 providesindicators of deterioration to look forwhen conducting an inspection. A

qualified design professional will beable to recommend rehabilitativeaction to prevent these symptomsfrom developing into more severe,more costly, building envelope failures.

During inspections, it should be kept inmind that water is most likely topenetrate brick masonry walls through:

· failed mortar joints;

· parapets and copings;

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BrBrBrBrBrick Masonrick Masonrick Masonrick Masonrick Masonry Rehabilitationy Rehabilitationy Rehabilitationy Rehabilitationy Rehabilitation

The following representative projectsincluded brick masonry rehabilitation.

ChrChrChrChrChrysler Buildingysler Buildingysler Buildingysler Buildingysler BuildingNew York New YorkSpire and Facade Restoration

JPJPJPJPJP Morgan Chase and CoMorgan Chase and CoMorgan Chase and CoMorgan Chase and CoMorgan Chase and Co.....New York, New YorkBuilding Envelope Survey and Facade Restoration 15 Broad Street 37 Wall Street 43 Exchange Place

The Goodwin HotelThe Goodwin HotelThe Goodwin HotelThe Goodwin HotelThe Goodwin HotelHartford, ConnecticutFacade and Roof Restoration

Columbia UnivColumbia UnivColumbia UnivColumbia UnivColumbia UnivererererersitysitysitysitysityHammer Health Science CenterHammer Health Science CenterHammer Health Science CenterHammer Health Science CenterHammer Health Science CenterNew York, New YorkFacade Investigation and Rehabilitation

New New New New New YYYYYororororork City School Constrk City School Constrk City School Constrk City School Constrk City School ConstructionuctionuctionuctionuctionAuthorityAuthorityAuthorityAuthorityAuthorityLong Island City, New YorkExterior Building Maintenance Manuals and Facade Rehabilitation

Congregational ChurchCongregational ChurchCongregational ChurchCongregational ChurchCongregational ChurchUnited Church of ChristUnited Church of ChristUnited Church of ChristUnited Church of ChristUnited Church of ChristNaugatuck, ConnecticutSteeple and Parish House Rehabilitation

Fairfield Public SchoolsFairfield Public SchoolsFairfield Public SchoolsFairfield Public SchoolsFairfield Public SchoolsFairfield, ConnecticutBuilding Envelope Rehabilitation

UnivUnivUnivUnivUnivererererersity of Marsity of Marsity of Marsity of Marsity of MarylandylandylandylandylandEastern ShoreEastern ShoreEastern ShoreEastern ShoreEastern ShoreStudent Development CenterStudent Development CenterStudent Development CenterStudent Development CenterStudent Development CenterPrincess Anne, MarylandFacade Rehabilitation

25 Sigourney Street25 Sigourney Street25 Sigourney Street25 Sigourney Street25 Sigourney StreetHartford, ConnecticutBuilding Envelope Survey and Rehabilitation

The Smithsonian InstitutionThe Smithsonian InstitutionThe Smithsonian InstitutionThe Smithsonian InstitutionThe Smithsonian InstitutionThe Renwick GallerThe Renwick GallerThe Renwick GallerThe Renwick GallerThe Renwick GalleryyyyyWashington, District of ColumbiaWater Infiltration Remediation

Columbia UnivColumbia UnivColumbia UnivColumbia UnivColumbia Univererererersitysitysitysitysity44 Morningside Drive44 Morningside Drive44 Morningside Drive44 Morningside Drive44 Morningside DriveNew York, New YorkBuilding Envelope Rehabilitation

IBM CorporationIBM CorporationIBM CorporationIBM CorporationIBM CorporationSouthbury, ConnecticutBuilding Envelope Rehabilitation

UnivUnivUnivUnivUnivererererersity of Connecticutsity of Connecticutsity of Connecticutsity of Connecticutsity of ConnecticutDodd Dodd Dodd Dodd Dodd ArchivArchivArchivArchivArchives Research Centeres Research Centeres Research Centeres Research Centeres Research CenterStorrs, ConnecticutBuilding Envelope Rehabilitation

The GeorThe GeorThe GeorThe GeorThe George ge ge ge ge WWWWWashington Univashington Univashington Univashington Univashington UnivererererersitysitysitysitysityStuarStuarStuarStuarStuar t Hallt Hallt Hallt Hallt HallWashington, District of ColumbiaFacade Rehabilitation

VVVVVerererererizizizizizon Common Common Common Common CommunicationsunicationsunicationsunicationsunicationsNew York, New YorkLocal Law 11 Repairs and Building Envelope Rehabilitation Multiple Buildings in Brooklyn and Manhattan

YYYYYale Univale Univale Univale Univale Univererererersity School of Medicinesity School of Medicinesity School of Medicinesity School of Medicinesity School of MedicineSterSterSterSterSterling Hall of Medicineling Hall of Medicineling Hall of Medicineling Hall of Medicineling Hall of MedicineNew Haven, ConnecticutBuilding Envelope Rehabilitation

Scholastic PublishingScholastic PublishingScholastic PublishingScholastic PublishingScholastic PublishingNew York, New YorkBuilding Envelope Rehabilitation 555 Broadway

PfPfPfPfPfizizizizizererererer,,,,, Inc Inc Inc Inc Inc.....Global Manufacturing FacilityGlobal Manufacturing FacilityGlobal Manufacturing FacilityGlobal Manufacturing FacilityGlobal Manufacturing FacilityBrooklyn, New YorkBuilding Envelope Rehabilitation

1000 1000 1000 1000 1000 Thomas JeffThomas JeffThomas JeffThomas JeffThomas Jefferererererson Street,son Street,son Street,son Street,son Street, NW NW NW NW NWWashington, District of ColumbiaFacade Rehabilitation

Capital Community CollegeCapital Community CollegeCapital Community CollegeCapital Community CollegeCapital Community College(Historic G. Fox Building)(Historic G. Fox Building)(Historic G. Fox Building)(Historic G. Fox Building)(Historic G. Fox Building)Hartford, ConnecticutFacade and Roof Rehabilitation

IBM Corporation Advanced BusinessInstitute Palisades, New York. HoffmannArchitects’ project work included masonryrehabilitation of facades at this corporatetraining facility.

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JOURNAL is a publication of HoffmannArchitects, specialists in therehabilitation of building exteriors.The firm’s work includes investigative andrehabilitative architecture/engineeringservices for the analysisand resolution of problems withinroofs, facades, glazing, and structuralsystems of existing buildings, plazas/terraces, and parking garages.

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Figure 3Concave/roddedtooling of mortarjoints is recommendedas the most effectivetooling for preventingwater infiltration.

· sills, cornices and belt courses;

· areas of failed/inadequate flashing;and,

· failed sealant joints.

In addition to periodic inspections,routine maintenance plays animportant role in the longevity ofexterior brick masonry walls. Not onlyshould cavities be kept clean and freeof debris during and after construction,facades should be kept clean ofpollutants and free of vegetation, suchas vine growth, which can penetratethe masonry, facilitating waterinfiltration.

Conclusion

Exterior brick masonry walls are durable,but they are susceptible to inevitabledeterioration, as are all building envelopesystems. Understanding and resolvingthe root causes of deterioration is criticalto the development of lastingrehabilitation solutions. Routineinspections and preventative maintenanceand repairs are crucial in promoting thelongevity of these facades. By inspectingwalls on a routine basis, areas of minordeterioration can be detected andrepaired before they escalate into moresevere, and more costly, problems.

The most common and inevitable brickmasonry problem is deterioratedmortar joints. Proper repointing ofmortar joints requires:

· careful removal of deteriorated,inappropriate or loose mortar ;

· cleaning the joints of old mortar anddir t; and,

· installation of an appropriate—flexible, yet durable—mortar.

During mortar installation, propertooling of joints will ensure that mortar

fills them completely. Ideally, they will betooled to achieve a concave (orrodded) surface that is optimal fordirecting water off of a brick face (SeeFigure 3). Improper tooling allows waterto rest in joints, threatening to entermasonry walls.

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