John J. Hoffmann, FAIA and Russell M. Sanders, AIA

Journal of architectural

technology published

by Hoffmann Architects,

specialists in the rehabilitation

of building exteriors.

I S S U E 2 / 2 0 0 2 � V O L U M E 20 � N U M B E R 2

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Troubleshooting the Building Envelope:Addressing CAUSES, Not Symptoms

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he various components of the buildingenvelope—façades, roofing systems,windows—and parking structures, plazas/terraces/sidewalks, etc., inevitablydeteriorate over time. The culprits? Waterinfiltration, thermal expansion andcontraction, improper construction and/orsubstandard materials, structuralmovement or stress, and age.Maintenance of the building envelope iscritical to preserving not only the structuralintegrity of a building’s exterior but also toprotecting a building’s interior occupiedspaces; it serves as a barrier from theexternal environment.

Critical to maintaining the buildingenvelope is the ability of the facilitymanager, property manager or buildingengineer to recognize and address earlyindicators of deterioration. Costsassociated with deferred maintenanceincrease exponentially over time. Thereturn on interior investments—to lobbies,offices, restrooms—will significantly diminishif water infiltration disrupts tenant activitiesand causes irrevocable damage to ceilings,walls, windows and floor finishes.

Recognizing early indicators ofdeterioration is no less critical for parkingstructures, plazas, terraces and sidewalks.These elements suffer the damagingeffects of pedestrian and vehicular traffic,

and the corrosive impact of acid rainand de-icing salts. The risk associatedwith deterioration in these structures issevere; the threat of costly and time-consuming lawsuits associated withdriving and/or tripping hazards,unacceptable.

What To Do When Trouble Strikes

Water infiltration can be counted on toexacerbate building envelope failures.Solutions to building envelope failuresaddress CAUSES, not symptoms, andcan be relied upon to keep water out ofbuilding envelope components in thefuture.

John J. Hoffmann, FAIA, Principal, and Russell M. Sanders, AIA, Director of Technical Services at HoffmannArchitects, are responsible for the technical quality and integrity of all projects produced by the firm.

Water infiltration, thermal expansion/contraction, improper construction orsubstandard materials, structural movement orstress, and age contribute to the inevitabledeterioration of building materials over time.

The key to successfully managing thebuilding envelope is knowing what todo when trouble strikes. Temporary orcosmetic measures—band-aids, if youwill—inevitably fail. The goal is to planand implement lasting solutions.

When trouble strikes, the first task is todefine the scope of work by:

· accurately attributing the nature andextent of problem;

· developing technically/aestheticallyappropriate, cost-effective remedialsolutions; and,

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J O U R N A L

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Troubleshooting Exterior Walls

Be they brick, stone, concrete, metal, glassor any combination of these, exterior walls

Anatomy of an Exterior Brick Wall

The basic components of brick veneerwall construction (refer to Figure 1)include the exterior face, the structure or“back-up,” and the cavity between thetwo; the flashing (which prevents thepassage of water into the structure fromthe joint); and the support angle. Typicalcauses of failure in this system include:

· absent or inadequate flashing;

· blocked water exit at flashing(blocked weep holes);

· failed or inadequate soft joints atrelieving angles; and,

· failed mortar or expansion joints.

Efflorescence, white stains and/or build-up of white, crystalline structures, is causedby the dissolution and surface deposition ofnaturally occurring salts.

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indicators of deterioration.

Figure 2, facing page, indicates types ofmortar joints and their effectiveness inpreventing water infiltration. Notethat the recommended joints are thosewhich direct water, a leading cause ofbuilding envelope failures, off of theexterior wall, as opposed to thosewhich permit water to rest in the joints.

· establishing probable construction cost.

Contract Documents are developed forthe designated scope of work, and bidsare solicited from capable and responsiblecontractors. Once construction isunderway, the design professional ensuresthat the work being performed by thecontractors is consistent with the work setforth in the Contract Documents.

By following these troubleshootingguidelines, a building manager can avoidthe costly surprises that occur wheninappropriate and/or poorly implementedrepairs fail.

Fig. 1 Relieving Angle Detail at End Wall

Flashing

Brick

Sealant

Compressible JointFiller

Support Angle

Weeps

are intended to separate us from theelements. Periodic surveys of exteriorwalls should be conducted to detectindicators of deterioration.

Brick ExteriorsBrick ExteriorsBrick ExteriorsBrick ExteriorsBrick Exteriors

Bricks have been used as building blocksfor centuries, for structures ranging fromthe adobe (mud brick) homes andmissions in the southwestern UnitedStates to all manner of contemporarybuildings. Common to all brick exteriors,however, is the necessity for consistentmaintenance and repairs to ensure theiruseful life for as long as possible.

Brick exterior walls should be checkedregularly for failed/aging mortar joints.De-bonding, cracked/spalled brick, andefflorescence/water staining are

Stone & Pre-cast Concrete ExteriorsStone & Pre-cast Concrete ExteriorsStone & Pre-cast Concrete ExteriorsStone & Pre-cast Concrete ExteriorsStone & Pre-cast Concrete Exteriors

The proper care and preservation ofsealant joints is key to preserving theuseful life of concrete and stone exteriors.

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V O L U M E 20 � N U M B E R 2

Concave/Rodded(Recommended)(Recommended)(Recommended)(Recommended)(Recommended)

“V” Shaped(Recommended)(Recommended)(Recommended)(Recommended)(Recommended)

Weathered(Recommended)(Recommended)(Recommended)(Recommended)(Recommended)

Extruded(((((Not Not Not Not Not AcceptabAcceptabAcceptabAcceptabAcceptablelelelele)))))

Struck(((((Not Not Not Not Not AcceptabAcceptabAcceptabAcceptabAcceptable)le)le)le)le)

Flush/Plain Cut(((((Acceptable)Acceptable)Acceptable)Acceptable)Acceptable)

Flush & Rodded(((((Acceptable)Acceptable)Acceptable)Acceptable)Acceptable)

Ruled(((((Acceptable)Acceptable)Acceptable)Acceptable)Acceptable)

Raked(((((Not Not Not Not Not AcceptabAcceptabAcceptabAcceptabAcceptable)le)le)le)le)

Beaded(((((Not Not Not Not Not AcceptabAcceptabAcceptabAcceptabAcceptable)le)le)le)le)

Fig. 2 Types of Mortar Joints (In Profile)

lifespan of a stone or concrete exteriorwall.

Exterior joints must be properly sealedbetween:

· individual panels;

· windows, frames and exterior walls; and,

· any two or more building envelopecomponents.

Sealant materials should accommodatedifferential movement in various buildingsystems and bond properly to differentbuilding materials. At installation,

Sealant failure between aluminum panels.>

(continued on page 4) Cohesive joint failure.>

How exterior joints are sealed, theselection of sealant materials, andinstallation considerations all playimportant roles in determining the

consideration should be given to jointwidth limitations, preparation of surfacesto improve bond, and exteriortemperature. Lastly, it is important toevaluate/ensure the integrity of anchorsystems when conducting inspections ofconcrete and stone exteriors.

(Glass) Cur(Glass) Cur(Glass) Cur(Glass) Cur(Glass) Curtain tain tain tain tain WWWWWalls & alls & alls & alls & alls & WWWWWindoindoindoindoindow Systemsw Systemsw Systemsw Systemsw Systems

When caring for (glass) curtain wall andwindow systems, a building managershould:

· routinely examine window gaskets orsealant for splits, breaks or openings;

· replace failed gaskets or sealants thathave dried, cracked, shrunken orotherwise exceeded their useful life; and,

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J O U R N A L

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Troubleshooting Roofing Systems

Whether low slope or steep slope,regardless of materials and/orconstruction, all roofing systemsinevitably deteriorate over time.

During a roof inspection, problemareas should be examined to detectthe root causes of deterioration andto determine the most effective repairsolutions. Deterioration increasesexponentially over time. To put itsimply, the longer it sits, the moredamage it will do to the structure.Early detection and pro-activemaintenance and repairs enable abuilding manager to avoid more costlyroof repairs and/or replacements inthe future.

Successful design solutions for roofingsystems allow for differentialmovement, properly integrate/curbrooftop equipment, and provide forfoot traffic.

Ponding (water retention on the roofmembrane) can occur in low slope roofingsystems.

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Note cracks in these damaged ballastpavers (in a low slope system).>

Open seams/solder joint failure areindicators of deterioration in metal systems.Proper care during application of roofingmaterials is critical to preserving a roof ’suseful life.

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Troubleshooting Plazas/Terraces

Plazas/Terraces often serve as populargathering places, for both building tenantsand area pedestrians. These heavilytrafficked areas may incorporatelandscaping and lighting design, reflectingpools and fountains, and may evenshowcase the work of area sculptors. Atthe hands of Mother Nature, plazas/terraces are continuously exposed to thefull force of the elements.

What about plazas will plague you?What about plazas will plague you?What about plazas will plague you?What about plazas will plague you?What about plazas will plague you?

Plazas over occupied spaces are part ofthe building envelope. While water isclearly the enemy of any part of thebuilding envelope, it is particularly harmfulto horizontal surfaces. Standing water onhorizontal surfaces, on plazas and terraces,accelerates deterioration.

Inadequate drainage and prematurelyfailed waterproofing membranes aredetrimental to a plaza’s useful lifespan.Ponding, water stains, cracks, spalls andheaved pavers (which create trippinghazards) are the indicators of trouble.Protection of the waterproofingmembrane and sufficient drainage are thesolutions.

Glass curtain wall and window systemsat a suburban corporate office park.

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Indicators of failure differ with the varioustypes of roofing systems. They include:

· in low slope systems: ponding, cracks,blisters, holes or splits;

· in metal systems: pitting, corrosion, openseams/solder joint failure; and,

· in clay tile and slate roof systems: loosetile, broken tile, failed/deterioratedfasteners.

The most prevalent roofing applicationand repair errors are the results ofinattention to detail, the use ofincompatible or inappropriate materials,and improper installation.

An historic mansard roof (having oneach side a steeper lower part and ashallower upper part) with terra cotta tiles.

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· inspect mullions for deterioration.

Glass that appears “fogged” shouldnot be neglected. It may besymptomatic of a compromisedthermal seal.

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V O L U M E 20 � N U M B E R 2

Fig. 3 Plaza Drain

Water should be allowed to drain bothat the wearing surface and beneath theplaza surface at the membrane.Drainage may occur at varying degreesof slope: paved surfaces with tables andchairs should be more level, while it isgenerally recommended that drainage atthe membrane should occur at 1/4” perfoot. In order for drainage systems toremain effective, drains must beconsistently maintained. They should beperiodically checked and cleared ofdebris.

The bi-level plaza drain assembly inFigure 3 above shows a loose laidassembly, but the same results areachievable with pavers in a mortarsetting. Typical trench drains are notmanufactured as bi-level drains, causingwater to stand at the membrane level.

Drain Cover

Plaza Paver

Pedestal

Underlayment Mat

Rigid Board Insulation

Drainage Composite

Waterproofing Membrane

Debris should be cleared of drains toensure their effectiveness. Note cracks whichpermit water entry.

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Plazas/terraces often incorporate seating,planters, and lighting design, all of which mustbe considered when planning maintenanceand repairs.

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Troubleshooting Parking Structures

In a society where drivers abound and

land is at a premium, parking structuresare an integral part of the commerciallandscape. They can be constructed ofpre-cast concrete, cast-in-place concrete, orsteel with a concrete deck.

Parking structures deteriorate morerapidly than other built structures as theysuffer the damaging effects of vehiculartraffic and the corrosive impact of acid rainand de-icing salts. This is in addition towater infiltration, thermal expansion andcontraction, improper construction and/orsubstandard materials.

Symptoms of water infiltration in parkingstructures include efflorescence, cracks andspalls.Building managers should beware ofcracks on surface slabs that permit waterto enter the concrete. But it should beremembered that deterioration beginswithin the slab, out of view. Damagevisible from the deck is often only the tipof the iceberg.

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J O U R N A L

Troubleshooting Historic & LandmarkStructures

Historic/landmark building exteriors areoften constructed with materials andtechniques uncommon to contemporaryconstruction and can presentmaintenance/rehabilitation challenges. It isoften essential to develop a conciseapproach to address maintenance needs,remedial repairs, and modifications orrestoration work to the buildingenvelope.

Other considerations for the successfulmanagement of historic/landmarkstructures include:

· landmark status (national or local) andrelated rehabilitation guidelines/restrictions;

· local building codes;

· primary building function and tenantrequirements; and,

· budget.

A tremendous financial burden can beplaced on the building owner of ahistoric/landmark structure. The properremediation or restoration of the exteriormay cost two to three times the value ofthe building.

Unique MaterUnique MaterUnique MaterUnique MaterUnique Materials & ials & ials & ials & ials & TTTTTechniquesechniquesechniquesechniquesechniques

Construction materials that are moreprevalent in historic structures than incontemporary structures include terracotta, tile (mosaic, clay, ceramic), anddecorative/ornamental grating (iron,aluminum, stainless steel). Constructiontechniques include intricate patternswithin brick, stone, terra cotta, and tile;narrow joint widths among brick andstone; and obsolete structural/anchorsystems.

(continued from page 5)

preventing the development of negativeconditions. And, preventativemaintenance techniques, such as theapplication of an appropriate coating orsealer to protect new decks fromcorrosion, can be effective.

When repairs become necessary, theextent of the damage must bedetermined and the area properlyquantified to effect lasting solutions. Thiscan be accomplished using simplemethods such as chain dragging orsound tapping the surface to identifydelamination. More extensive testing ofconcrete may be needed to determineits integrity and the true nature andextent of deterioration. Tests thatmeasure compressive strength, depth ofcarbonation (which reduces the naturalability of concrete to protect embeddedreinforcement steel), and chloride ioncontent (from road salts) can be

Large, stainless steel replicas of automobilehood ornaments adorn the landmarkedChrysler Building. Over the years, roofingmastic, sealant and other incompatiblematerials were used to make repairs, all ofwhich exacerbated negative conditions.

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Intricate patterns and decorativeelements can present challenges whenrehabilitating historic structures.

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Case in point: when cracks (which candevelop on the top surface for anynumber of reasons) permit water toenter the concrete, the steel reinforcingbars that are embedded within theconcrete for stength begin to rust. Asthe steel rusts, it pushes the concreteaway, causing it to chip and spall—riskingdamage to vehicles and injuries topeople.

instrumental in developing appropriaterepairs that go beyond surface damageand correct deterioration at its core.

Pro-active Maintenance Is KeyPro-active Maintenance Is KeyPro-active Maintenance Is KeyPro-active Maintenance Is KeyPro-active Maintenance Is Key

Parking structures require consistentmaintenance. Conducting regular visualexaminations to identify potentialproblem areas goes a long way toward

Spalls, laminations that break off due tocorrosion of reinforcement/embeddeditems, are among the indicators of failure inparking structures.

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Conclusion

Failure to identify and address buildingenvelope “hot spots”—portents ofdeterioration—will ultimately result insignificant expense to building owners.People, the power of nature, and thepassage of time can be relied upon toadversely impact the building envelope.Early detection, however, can be apowerful weapon in the fight againstbuilding envelope deterioration; it allowsfor the development of pro-activemaintenance and repair programs thatminimize tenant disruption and maximizea building owner’s return on investment.

V O L U M E 20 � N U M B E R 2

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Building EnvelopeBuilding EnvelopeBuilding EnvelopeBuilding EnvelopeBuilding Envelope Rehabilitation Rehabilitation Rehabilitation Rehabilitation Rehabilitation

Hoffmann Architects has developed andimplemented building envelope rehabilita-tion solutions for a number of itscorporate, industrial, academic, municipal,and ecclesiastical clients, including:

New New New New New YYYYYororororork Stock Exchangek Stock Exchangek Stock Exchangek Stock Exchangek Stock ExchangeNew York, New YorkFacade & Roof Rehabilitation

The Goodwin HotelThe Goodwin HotelThe Goodwin HotelThe Goodwin HotelThe Goodwin Hotel*Hartford, ConnecticutFacade & Roof Restoration

VVVVVerererererizizizizizon Common Common Common Common CommunicationsunicationsunicationsunicationsunicationsNew York, New YorkFacade & Roof Rehabilitation

Columbia UnivColumbia UnivColumbia UnivColumbia UnivColumbia UnivererererersitysitysitysitysityNew York, New YorkRoof & Facade Rehabilitation

J.PJ.PJ.PJ.PJ.P..... Mor Mor Mor Mor Morgan Chase & Cogan Chase & Cogan Chase & Cogan Chase & Cogan Chase & Co.,.,.,.,., Incor Incor Incor Incor IncorporporporporporatedatedatedatedatedNew York, New YorkBuilding Envelope Survey & Facade Restoration23 Wall Street Complex 23 Wall Street 15 Broad Street 37 Wall Street 43 Exchange Place

IBM CorporationIBM CorporationIBM CorporationIBM CorporationIBM CorporationPoughkeepsie, New YorkRoof & Masonry Rehabilitation

Rockefeller Center ComplexRockefeller Center ComplexRockefeller Center ComplexRockefeller Center ComplexRockefeller Center ComplexNew York, New YorkExterior Restoration

TTTTTrrrrrinity Collegeinity Collegeinity Collegeinity Collegeinity CollegeHartford, ConnecticutRehabilitation Master Plan

One Beacon StreetOne Beacon StreetOne Beacon StreetOne Beacon StreetOne Beacon StreetBoston, MassachusettsParking Garage Repair & Plaza Rehabilitation

The Bank of New The Bank of New The Bank of New The Bank of New The Bank of New YYYYYorororororkkkkkNew York, New YorkRoof & Facade Rehabilitation

25 Sigourney Street25 Sigourney Street25 Sigourney Street25 Sigourney Street25 Sigourney StreetHartford, Connecticut(State of Connecticut)Building Envelope Rehabilitation & Re-Roofing

Smithsonian InstitutionSmithsonian InstitutionSmithsonian InstitutionSmithsonian InstitutionSmithsonian InstitutionWashington, District of ColumbiaCopper Roof Restoration National Museum of American Art, National Portrait Gallery & Archives of American Art

ChrChrChrChrChrysler Buildingysler Buildingysler Buildingysler Buildingysler Building*New York, New YorkSpire & Facade Restoration

PfPfPfPfPfizizizizizererererer,,,,, Inc Inc Inc Inc Inc..... WWWWWorororororld Headquarld Headquarld Headquarld Headquarld HeadquartertertertertersssssNew York, New YorkFacade & Roof Rehabilitation

New New New New New YYYYYororororork City School Constrk City School Constrk City School Constrk City School Constrk City School ConstructionuctionuctionuctionuctionAuthorityAuthorityAuthorityAuthorityAuthorityNew York, New YorkBuilding Envelope Rehabilitation

General Electric CompanyGeneral Electric CompanyGeneral Electric CompanyGeneral Electric CompanyGeneral Electric CompanyCorCorCorCorCorporporporporporate Headquarate Headquarate Headquarate Headquarate Headquartertertertertersssss

Fairfield, ConnecticutFacade, Roof & Parking Garage Rehabilitation

United Nations ComplexUnited Nations ComplexUnited Nations ComplexUnited Nations ComplexUnited Nations ComplexNew York, New YorkDome & Roof Rehabilitation

United States Capitol ComplexUnited States Capitol ComplexUnited States Capitol ComplexUnited States Capitol ComplexUnited States Capitol Complex*Washington, District of ColumbiaRestoration

XeroXeroXeroXeroXerox Corx Corx Corx Corx Corporporporporporation Headquaration Headquaration Headquaration Headquaration HeadquartertertertertersssssStamford, ConnecticutFacade Rehabilitation

(continued on page 8)

Verizon Communications HeadquartersNew York, New York.

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432 Washington AvenueNorth Haven, Connecticut 06473

ADDRESS SERVICE REQUESTED

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.

Please send news, technical information,address changes, or requests for freesubscriptions to Editor, HoffmannArchitects JOURNAL, 432 WashingtonAvenue, North Haven, Connecticut06473. For answers to specific questionsor for information on the servicesHoffmann Architects offers, please contactSandra Matheny at

(203) 239-6660.

432 Washington AvenueNorth Haven CT 06473203 239-6660

500 Fifth Avenue, Suite 830New York NY 10110212 789-9915

1001 Connecticut Avenue NW, Suite 825Washington DC 20036202 530-1100

For more information on thetopics discussed in this article,visit us on the web atwww.hoffmannarchitects.com,or contact us atemail@hoffmannarchitects.com.

Editor & Graphic Services:Maryellen Apelquist

PRSRT STDU.S. POSTAGE

PAIDPERMIT NO. 426WATERBURY, CT

J O U R N A L

Hoffmann Architects designed an award-winning program to restore the Queen Anne-styleGoodwin Hotel, originally constructed in the 1880s.

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FoFoFoFoFoxwxwxwxwxwoods Resoroods Resoroods Resoroods Resoroods Resort Casinot Casinot Casinot Casinot CasinoMashantucket, ConnecticutRehabilitation Grand Pequot Parking Garage Great Cedar Parking Garage

PrPrPrPrPrudential Insurudential Insurudential Insurudential Insurudential Insurance Companance Companance Companance Companance CompanyyyyyEastern Operations OfficeEastern Operations OfficeEastern Operations OfficeEastern Operations OfficeEastern Operations OfficeKing of Prussia, PennsylvaniaBuilding Envelope Rehabilitation

1166 1166 1166 1166 1166 AAAAAvvvvvenenenenenue of the ue of the ue of the ue of the ue of the AmerAmerAmerAmerAmericasicasicasicasicasNew York, New York(Marsh & McLennan Headquarters)Plaza, Facade & Roof Rehabilitation

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The HarThe HarThe HarThe HarThe HartftftftftfordordordordordCorCorCorCorCorporporporporporate Headquarate Headquarate Headquarate Headquarate HeadquartertertertertersssssHartford, ConnecticutBuilding Envelope Rehabilitation, Master Plan, Facade Restoration & Roof Replacements

Lincoln Center fLincoln Center fLincoln Center fLincoln Center fLincoln Center for the Por the Por the Por the Por the Perferferferferforororororming ming ming ming ming ArArArArArtststststsNew York, New YorkRoof & Facade Restoration Metropolitan Opera House Avery Fisher Hall Vivian Beaumont Theatre

* Denotes an award-winning project.