Expansion Joints in Roofing

8/2/2019 Expansion Joints in Roofing

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DUAL-SEALEDMOVEMENT JOINTS INROOFINGANDWATERPROOFINGAPPLICATIONS

ROCCOROMERO,AIAWISS,JANNEY,ELSTNERASSOCIATES, INC.

960S.HarneyStreet,Seattle,WA98108Phone:206-622-1441Fax:206-622-0701 E-mail: [email protected]

S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y OC T O B E R 2 0 0 9 R O M E R O
mailto:[email protected]:[email protected]


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ABSTRACTExpansionjointsareoftenthemostchallengingaspectofroofingorwaterproofingmem-

branesystemdesignonbothnew installationsandreplacementprojects.Whilethe fieldofthe membrane is generally predictableandwell detailed bymembrane manufacturers, thetransitionofthemembranesatexpansionjointscanbeuniquetoeveryproject.

When designing expansion joints, dual-seal systems can be considered to providelonger-term waterproofing performance.This approach involves utilizing the roofing andwaterproofingmembraneas theprimaryassembly,alongwitha flexiblegland that iscom-patiblewiththeroofingorwaterproofingmembraneasthesecondaryseal.

SPEAKERROCCOROMERO,AIAWISS,JANNEY,ELSTNERASSOCIATES, INC.

SincejoiningWiss,Janney,ElstnerAssociates, Inc.over20yearsago,Mr.Romerohasbeeninvolvedinawiderangeofinvestigationandrepairprojectsthatincludeexteriorbuild-ingenvelopesystems.Hehasspecialexpertiseintheinvestigationanddesignofrepairsforvariouswaterproofingandroofingsystems.

Mr.RomerosrecentworkincludesreplacementoftheterracewaterproofingsystemsattheOregonStateCapitol inSalem,OR,andtheWashingtonStateCapitol inOlympia,WA;and roofing replacement at the Yale Center for British Art in New Haven, CT, and theAnchorageMuseumatRasmusonCenterinAnchorage,AK.

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Figure 1 Copper waterstop.

DUAL-SEALEDMOVEMENT JOINTS INROOFINGANDWATERPROOFINGAPPLICATIONS

Expansionjoints and seismicjoints areoften

the

most

challenging

aspect

of

roofing

or waterproofing membrane system design,both on new installations and as part ofreplacement projects. While the field of themembrane isgenerallypredictableandwelldetailed by membrane manufacturers, thetransition of the membranes at movement

jointscanbeunique toeveryproject.Closeattentiontothesecriticalareasisneededtopreventwaterleakageintothebuildinginte-rior and localized failure of the membranesystem. In many waterproofing applica-tions, architectural paving or other archi-tectural finishes make it difficult andexpensive to inspect and repair distressed

joint assemblies. Proper detailing of thesecritical conditions is therefore essential tosuccessful long-term performance of thewaterproofingsystem.

When designing the waterproofing aspect of movement joints, dual-seal sys-tems should be considered to providelonger-term waterproof performance. Thisapproachofredundantsealsinvolvesutiliz-ing the roofing and waterproofing mem-brane as the primary assembly and incor-porating a flexible gland as the secondaryseal. The design for a dual seal shouldinclude systems that shed waterand,mostimportantly,thatcanbeadaptedtoexistingconditions.BACKGROUND

The use of sealed movementjoints inbuildings is a concept that has developedoutoftheneedtokeepjoints fromallowingwater penetration to building interiors orout of water tanks and other structures.Historically, movementjoints in horizontalapplications used a copper waterstop setinto thejoint as the waterproofing compo-nent of thejoint.Laps in the copperwater-stopweretypicallythree-quartersofaninchandfullysoldered.Semiflexiblefillermateri-alswereadded into theopenportionof the

joint above the waterstop and capped offflushwiththetopofthejointwithmasticorlead. These semiflexible filler materialsincludedcompositionasphaltandvegetablefiber, composition asphalt and cork, and

asphalt-based compounds thatare

used

as

mastics.

In

concrete

slabapplications,copperwater-stopswere installedasapartofthe initial concrete placement,with the waterstop flanges castintotheedgesofthejoint.

In order to accommodatemovement, the profile of thecopper waterstop required astandingribortrough;however,troughscouldcollectinfiltratingwaterandallowednomeans fordrainagetothebuildingexterior(Figure 1). Several designs forflexible, water-resistant plasticwaterstops and flashing stripswere registered with the UnitedStates Patent Office beginning in the early1940s.

In contemporary design, movementjoints are a part of the building envelopeand generally occur at seismic joints,expansion joints, and isolation joints.Movement joints in buildings commonlyoccur at changes in the structural system,between adjacent buildings, and betweenadjacent, dissimilar building envelopematerials. A brief description of movement

joints isas follows: Expansion joints are designed to

allowtheexpansionandcontractionof materials and system compo-nents, such as expansion of brickmasonryandconcretecreep,aswellas to accommodate thermal move-mentofmaterials.

Isolation joints are used to sepa-rate systems from each other andextend through the entire buildingsystemorassembly.Thesejointsaredesigned to allow components tomove independently of one anotherand are used to isolate differentroofingmembranesystemsoratthetransition of a slab-on-ground to acolumn footingoradjacentwall.

Seismic joints are wider thanexpansion and isolationjoints andare designed to separate buildingssothatthebuildingscanmoveinde-

pendently of one another duriseismic activity and minimize daage from building-to-building cotact.

While the waterproofing integrity of tassembly is often well designed over texpanse of the roof, foundation, terrace,plaza, the interface of waterproofing sytemswithmovementjoints,whichiscritito the overall watertight integrity of tcompleted system, is often not understoas well. While leakyjoints that allow waintrusion into the buildings interior spaare readily detected and a nuisance, wathat infiltrates underneath the roofimembrane or into the exterior wall systemay cause undetected and more sevedamage and deterioration of building coponents.CASESTUDIES

Three case studies of projects whedual-sealedmovementjointsweredesignare presented herein and include both nconstruction and retrofit designs. Theprojects include the Oregon State CapiterracerenovationprojectinSalem,OR;tEmeraldQueenHotelandCasinonewcostruction project in Fife, WA; and tAnchorage Museum at Rasmuson Cenroofing replacement project in AnchoraAK.



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Figure 2 Debonded waterproofing membrane and unsealed gasket at jointsubstrate.

Figure 4 Gap at end of steel bent-platesill support at existing gasket.

Figure 3 Seismic joint at terrace planterwall below window.

OREGONSTATECAPITOLTERRACEWATERPROOFINGRENOVATIONPROJECT

ThecurrentOregonStateCapitolbuild-ingwasconstructed in1938 in Salem,OR.In 1977, the building was enlarged withnew additions, including three office towerwings linked together at the first- and sec-ond-floor levels. The second-floor terracewas

accessible

from

the

east

or

west

office

wingsordirectly from thegovernorsoffice.At the first floorbelowtheterrace,buildingfunctions included a public lobby entranceand hearing rooms. The original terraceconstruction consisted of a structural con-crete-composite slab/joist system coveredbyawaterproofingmembranesystem,mor-tar-setting bed, slate pavers sloped totrench drains, and integral concreteplantersattheterraceperimeter.

Theterracewasoriginallydesignedasastructure independentof the Capitolbuild-ingandadjacenteastandwestofficewings;thus, a seismicjoint existed at the perime-teroftheterraceonthreesides.Waterleak-ageat the seismicjointshad infiltrated themembrane flashing, which suffered fromadhesive failure at the substrate andpassed between the gasket and concretesubstrateatthejointinterface(Figure 2).Inthis system, the gasket was dry-fitted intothejointandalsohadgapsalong its lengthat butt joints. While the gasket providedback-up support that allowed the mem-brane to bridge the width of thejoint, thegasket itself was not installed as an inde-pendentwaterproofingcomponent.

In 2008,as a partof the buildingreno-vation, the terrace-level waterproofing sys-tem was removed and replaced. The newwaterproofing membrane system consisted

of a reinforced, hot-applied, rubberized- braneswereremovedattheseismicjoints.asphalt membrane system applied to the Thenewtoppingslabwouldlimitfuturetopofthestructuralslab,aprotectionlayer, access to the waterproofing membrane atdrainage mat, and patterned architectural the seismic joint; therefore, a dual-sealconcrete top-ping slabsloped totrench drains.In the area ofthe water-proofing mem-brane replace-ment work, allexisting gas-ketsandmem-



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Figure 5 Gap between lowest edge osteel bent-plate sill support and top oplanter wall.

Figure 7 Sheet-metal closure component.

Figure 6 New stebent-plate extensio

movement-joint approach was used. The design utilized a preformed, acrylic-impregnatedexpandingfoamsealthatexpandstofillandsealthegapinthejoint.

Thispreformedsealwasconsideredtobethesecondsealorbackuplineofdefenseagainst water intrusion into the seismicjoint.The primary seal utilized a flexibleglandembeddedinalayerofhot-appliedrubberizedasphalt.Boththewaterproof-ing membrane manufacturer and foam seal manufacturer confirmed prior toinstallationthatthecomponentswerecompatiblewitheachother.

As with many retrofit projects, unique transitions between buildings requiredspecialized movement-joint waterproofing design. For example, at the north-perimeterplanterwalls,aseismicjointwaslocateddirectlybelowwindowsills,withgaps between the existingsteel bent-plate marble sillsupport and existing jointgasket (Figures 3 and 4).Removal of the gasketrevealeda gap between thelowest edge of the steelbent-plate sill support andthe top of the planter wall(Figure 5).

In order to install thepreformed acrylic-impreg-natedexpanding-foamseal,a new bent-plate extensionwas fabricated and at-tached to the existing steelbent-plate sill support(Figure 6). Sheet-metalflashing closure compo-nents were also fabricatedto span gaps so as to sup-port the new flexible glandthat became a part of thenew waterproofing mem-branesystem (Figure 7).

In order to verify adhe-

sionofthenewwaterproof-S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y OC T O B E R 2 0 0 9 R O M E R O


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Figure 8 Adhesion evaluation of newwaterproofing membrane at various substrates.

Figure 9 Secondary seal: preformed acrylic-impregnated expanding foam at directionchange in joint.

Figure 10 Primary seal: flexible glandembedded in waterproofing membrane.

Figure 11 Entire assembly coveredwith reinforced, hot-applied rubberized-

asphalt membrane system.

ing membrane system to the various substrates (which included marble, con-crete,andsteel),thesubstrateswerepreparedandprimedwhereapplicable,andmembranepatcheswere installedandevaluated (Figure 8).

Transitionsfromhorizontaltoverticalcomponentsrequiredspecialdetailinginordertomaintainthewatertightintegrityofthejoint.Atthepreformedacrylic-impregnatedexpanding-foamseal,portionsoftheendsof theverticalandhori-zontalcomponentsweremiter-cutata45-degreeangleandkeyedtogether.Thetopoftheexpandingfoamwassetlevelwiththetopedgeofthejointtoeliminatecreationofatroughthatcouldpotentiallycollectinfiltratingwater.Flexibleglandwas

then

installed

over

the

preformed

acrylic-impregnated

expanding-foam

seal

in a layer of hot-rubberized asphalt. As a part of the waterproofing membranesystem, a membrane flashing was installed directly over the flexible gland in alayer of hot-rubberized asphalt waterproofing. The reinforced waterproofingmembrane system was then installed, integrated with the membrane flashing(Figures 9,10,and11).

Another difficult seismic-joint transition occurred where the planter wallsterminatedatthebuildingsdoorwayentrances.Becausetheexistingmarblewas



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Figure 12 Partial mock-up depicting construction of wood-blocking datum.

keyed into a masonry backup wall,severaldirectionalchangesoccurredin the movement joint. The pre-formed,acrylic-impregnatedexpand-ing-foam seal was field-cut and fittogetherwithmiteredcornerstopro-vide a waterproof secondary seal.

The primary seal flexible gland wasinstalled in a layer of hot-appliedrubberized-asphalt

waterproofing.

Additional flexible gland was in-stalled vertically up the planter atthe movement joint in a ship lapmanner and set in a layer of hot-appliedrubberizedasphalt.Therein-forcedwaterproofingmembranesys-tem was fully installedand integrat-edwiththe flexiblegland,creatingamonolithic waterproofing membranesystem. This construction resultedin a completed assembly that wascontoured to the existing condition,and thus not reliant on numerouslayers of built-up field laps andsplices.

An important aspect of water-proof movement joints is that theverticalflashingcomponentbeproperlyter-minated. Water intrusion can occur if amembrane fails adhesively and debondsfrom its substrate.The installation of fullysealedterminationbarsattheverticallead-ing edge of the membrane is recommendedfor a long-term waterproofjoint.The com-pleted horizontal joint system should besuccessfully flood-tested and monitored,withnoleakagefor48hours,inaccordancewith ASTM D5957, Standard Guide forFlood-Testing Horizontal WaterproofingInstallations.EMERALDQUEENHOTELANDCASINOROOFINGPROJECT

In 2006, the Native American PuyallupTribe began construction of a new casinoand office-tower complex that annexed thenorth elevation of an existing circa-1980shotel. A 300-ft-long seismic joint wasdesigned between the existing hotel andnew two-story casino addition. The jointwas locatedaboveoccupiedbuildingareas.

The new casino roof construction con-sisted of a composite metal deck, vaporretarder, rigid insulation, and a mechani-cally attached, reinforced, 60-mil thermo-plasticolefin(TPO),single-plyroofingmem-brane.The roof deck sloped to a drainagetroughlocatedadjacenttotheseismicjoint.

Theexistinghotelexterior-wallconstructiongenerally consisted of vertical fluted con-

cretepierswithstuccoinfillpanelsandalu-minum-framed punched window units andpackaged terminal air-conditioner (PTAC)unitslocateddirectlybelowthewindows.Asa part of the limited hotel renovation, theexisting through-wall PTAC units wereremoved and an alternative HVAC systeminstalled, and the PTAC openings wereinfilledwithastuccowallassembly.

The most challenging aspect of water-proofingdesignforthismovementjointwasthat the exterior face of the fluted concretepiers and adjacent stucco panels were atdifferentplanesanddidnotalign;thus,theseismicjointgaprangedbetween2inatthefluted concrete piers and 6 in along thestuccocladding.Inaddition,sincethestuc-co cladding was part of the existing hotelexterior wall construction, it continueddownwardintotheseismicjoint.Waterthatinfiltrated the stucco system could bypassthe seismic joint seals and leak into thebuilding.

In order to address the gap created bythe stucco setback at the fluted concretepiers,continuouswoodblockingwasaddedto establish a datum line for the termina-tionpointoftheroofingmembraneandpro-vide a substrate to attach componentsrequiredforthemovementjoint(Figure 12).

Because the stucco cladding continueddownward into the movement joint, thestucco assembly required the addition of

new flashing above the movementjoint.accomplish this, a strip of stucco wremoved.Aportionoftheexistingmetallaand weather-resistive barrier was leftplace,andnewsheet-metalcounterflashiwas integrated. The existing weathresistive barrier of the stucco assemblappedoverthecounterflashing,providinnew drainage path and flashing systemthestuccowallsystem.

The single-ply TPO roofing membrawas utilized as the primary waterprooficomponent for the movementjoint. WhtheTPO membrane thickness was typica60 mils in the field of the roof, membrathickness was reduced to 45 mils at t

jointinordertofoldthemembraneandcate slack to accommodate anticipatmovement (Figure 13).

The foldedTPO membrane was termnated vertically at the new blocking. Tmembrane was installed with a slope-draintowardtheoutsideroofedgeand intheroofdrainagetrough.

Asheet-metaljointcoverwashookeda continuous cleat at the roof side of tcurbtoaccommodatemovementofthesemic joint. This cover was fabricated wfullysolderedcornersandsealedat lapsprovide a secondary water-shedding coponent for thejoint. Due to the irregusurface of the fluted concrete, a reglet wcut into the concrete surface to act as



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Figure 13 Partial mock-up of folds to create slack in TPO membrane toaccommodate movement. Note that the bottom layer of TPO membrane would havebeen cut off and terminated at the roof-side edge of the top of the curb, leavingenough length for the folded TPO membrane to be lapped and heat welded.

Figure 14 View of completed movement-joint assembly.

receiver for the sheet-metal counterflash-ing. Finally, one-component inside cornerswere fabricated with all seams solderedwatertight to address the transitionbetween the fluted concrete pier and theinsetstuccowallpanel.

Aviewofthecompletedsystemisshown in Figure 14. Several fieldmock-ups were performed to deter-mine the constructibility of thedesign and implement changes toaccommodateas-builtsubstratecon-ditions.ANCHORAGEMUSEUMATRASMUSONCENTERROOFINGREPLACEMENTPROJECT

The original Anchorage Museumat the Rasmuson Center buildingwas constructed in 1967, and build-ing additions were constructed in1974, 1982, and 2008. During aninvestigation, it was determined thattheexistingseismicjointbetweentheoriginalbuildingandthe1982build-ing addition was leaking water intothebuilding interior.

As a part of the roofing mem-brane replacement project for theoriginal 1967 building and the 1974and1982additions,theseismicjointwaterproofing system was rede-

signed. Along portions of the seismicjoint,the width of thejoint varied from 5 in tomore than 18 in. This joint was locateddirectly over occupied building space. Inordertopreventwarminteriorairfromflow-

ingintothejointandcondensingduringthewinter months, both a vapor retarder andinsulation system were designed for themovementjoint.

In order to support the vapor retarderand insulation, an aluminum bent-platesystem was designed that incorporated apreformed acrylic-impregnated expanding-foam seal. A fluid-applied elastomeric-waterproofing

membrane

was

designed

as

the vapor retarder for application over thesurface of the bent aluminum plate, fol-lowed by the installation of rigid boardinsulation.Thecombinationoftheexpand-ing-foamseal and fluid-appliedwaterproof-ing provide the secondary seal for thismovementjoint.

A single-ply ethylene propylene dienemonomer (EPDM) synthetic rubber roofingmembranewasselected forthenewroofingmembrane. It will be used to provide theprimarysealatthemovementjoint,appliedoveracoverboardontorigidinsulationthatis sloped toward the roof for drainage.TheEPDMmembranewasdesignedtobetermi-natedverticallyattheadjacentbuilding.Tohelp provide the necessary slack in theEPDM membrane to accommodate jointmovement, the EPDM membrane wasdesigned to be installed over a soft, com-pressible rod at the vertical-to-horizontaltransition. Sheet-metal joint covers andcounterflashing were designed with sealed



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Figure 15 Schematic seismic jointdetail.

Figure 16 Seismic-joint width transition componen

lapstoshedwaterandprovideanaddition-al layer of weatherproofing protection(Figure 15).

The most challenging aspect of thisdesign was the transition of joint widthsalong the length of thejoint. In this case,the joint width transitions occur at 90-degree directional changes in thejoint. Inordertomaintainthewatertightintegrityofthejoint, the aluminum bent plates were

theanticipatedmovementinthe joint. Flexible glandsandsheet-metaljointcoversshouldalsobe installed inawaterproof manner, shed-ding water away from the

joint and accommodatingmovement in thejoint. As aresource,ASTMC981,Stan-dard Guide for Design of

designedwithunique inside-to-outsidecor-ner components.These components allowtheexpanding-foamsealtobeacontinuouswidthatthecornertransitions (Figure 16),accommodating movement of thejoint.Thecorner components and bent-plate systemwere designed to be waterproofed with anelastomeric membrane. The elastomericmembrane will also be an air barrier, pre-ventingbuildinginteriorairflowfromenter-ingtheassembly.CONCLUSIONS

Dual-sealed movementjoints can pro-vide longer-term performance and shouldbeconsideredasanapproachtomovement-

joint waterproofing.The primary and sec-ondary seals should be installed as inde-pendentsystems thatprovideameasureofwaterproofing independent of one another.Ifgasketsorpreformedfoamsealsareusedaspartsofadual-sealedsystem,thesecom-ponents should be designed and installedsothattheyarewaterproofyetstillallowfor

Built-up Bituminous Mem- brane Waterproofing Sys-tems for Building Decks, provides generalexpansion-joint installation guidelines,which include raising the joint above thesurfaceofthedeckwiththeuseofcurbs.

When retrofitting existing movementjoints that are prone to water leakage,waterproofing and roofing systems shouldbeselectedthatcanbedesignedasintegralparts of thejoint systems.This approachhelps to reduce the number of materialsthatbecomepartoftheassembly,aswellasexpedites installation by utilizing tradesthatareonsite,performingthewaterproof-ingandroofingwork.

Oneprimaryadvantagetousingexperi-encedroofingandwaterproofingmembraneinstallers forjoint construction is that theyhave experience in the application of themembranematerialandgenerallyalsohaveexperience addressing problematic condi-tions such as inside and outside cornerconditions and membrane terminations.

Preformed foam seals and flexible glancan be used as part of a redundant watproofjoint,butthematerialsmustbecopatiblewith theothermaterialswithwhitheycome intocontact.Priortoimplemeing a dual-sealedjoint, the manufactureof the components that will make up t

jointmustreviewandapprovetheirmatealsandcomponentsasapartoftheassebly.

Changes in plane or direction are crcal areas of movement-joint design.Theareas should be specifically designed aspart of the construction documents

joint-seal installation. These details heidentify the need for preformed membracorners and one-component foam or glacorner components. Detailing of the ldimensions and treatments, slopes, aterminationsisalsoessentialforwaterpro

jointassemblies.Mock-upsareanintegralandimporta



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part of properjoint installation, and theyset the standard for acceptable installationon the project. When selecting a mock-uparea, consideration should be given toselecting a typical 90-degree transition, aswell as a location that requires changes inplane.Itisrecommendedthatmock-upsbeperformed prior to material being orderedfor the entire project, since the purpose ofthe

mock-up

is

to

confirm

the

constructibil-ityof thejointasdesignedusing thespeci-

fied materials and to verify that the rightmaterials and sizes have been ordered anddelivered for themock-ups.Toevaluate theexpertiseofthe installers, it isrecommend-ed that the mock-ups be performed by thesame installers who will be performing theworkontheproject.Mock-upsalsoprovidean opportunity for manufacturers to verifycompatibility of component materials, con-

firm the warranty, and provide additionalrecommendations.Themock-upperiodalsoallows time for the project team to refinedetailsasneededpriortothestartofwork.

As a part ofjoint-seal installation in awaterproofingapplication, theinstalledjointsealsshouldbewater-testedandmonitoredfor leakage in accordance withASTM D5957, Standard Guide for Flood

Testing

Horizontal

Waterproofing

Instal-lations, prior to installation of overburdenandconcrete-toppingslabsystems.REFERENCES

ASTMC981,StandardGuideforDesignof Built-Up Bituminous MembraneWaterproofing Systems for BuildingDecks.

ASTMD5957,StandardGuideforFloodTestingHorizontalWaterproofingIn-

stallations.Paul Porter and Susan Gibby, Oregon

State Capitol and the Capitol Mall,SalemOnline,http://iwa.cityofsalem.net /salemhistory/places/state_capitol.htm.

Charles George Ramsey and HaroldReeve Sleeper, Architectural GraphicStandards,5thed.,Wiley,NewYork,1956.

A.R.Santhakumar,

Movement

Joints

in

Buildings, Building Blocks, Novem-ber18,2006.

Water Stop Expansion Joint, PatentNumber 2,400,493, United StatesPatent Office, Albert C. Fischer,patent,May21,1946.

Waterstop for ExpansionJoints, PatentNumber 2,865,267, United StatesPatent Office, Alonzo W. Bailey,patent,December23,1958.

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Expansion Joints in Roofing

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