Case Study – San Diego Ba l l p a rk · to the Roman Bru n e l l e s c h i’s Do m e built of...

18 September 2004 v TileLetter

ow Ceramic Tile and Stone installers, distributors and manufacturers havea big opportunity to gain additional sales from exterior veneers as the result of thetesting performed during the construction of the new San Diego PETCOBallpark. The testing demonstrated that if installed correctly, ceramic tile andstone exterior adhered veneers are capable of significantly exceeding current seis-mic performance standards in California. This brings a new level of confidenceto adhered veneers, which should result in additional sales.

This article will discuss the history of using stone and ceramic tile exteriorveneers, and then in the form of a case study review the testing and the qualitycontrol process at PETCO Ballpark. Then I will review the various methods ofinstalling exterior veneers pointing out some of the differences and key factors toachieving a quality and safe installation.

Ceramic Tile, Brick and Natural Stone have a history of use for both their func-tionality and for their artistic qualities as artists and architects have used them forcenturies to distinguish their projects and to make artistic statements. These sur-faces are the most enduring and esthetically pleasing used for exterior ve n e e rcladdings (facades) in commercial and residential projects. Not only do these sur-faces function well, but also they add value and desirability to the pro p e rt y. Ofcourse these facades cost more to install, but their life cycle cost averages are muchl ower than a lot of other options, particularly when you re a l i ze they can last forthousands of years. T h e re is a choice of installation methods for these types of


facades and the costs and risks va ry. Asin any construction situation, thesep roducts are only as good as they areinstalled and limited to their intendeduse, and only as good as the substrate towhich they are applied. T h e re are alwaystrade-offs, but with good quality contro lplans the risks can be minimize d .

Natural Stone has been used in thec o n s t ruction of buildings for thou-sands of years. From the Gre a tPyramids of Giza built more than4,000 years ago, to the Jordan City ofPetra that was carved into the side of astone mountain over 2,000 years ago,to the Roman Bru n e l l e s c h i’s Do m ebuilt of stone in the fourteenth centu-ry. Ceramic Tile and brick have a longh i s t o ry of use for facades as we l l .Ceramic Tile was used on palace

facades and ancient walls of theBabylonians between 2,800 and 600BC. What these applications ofCeramic Tile, Brick and Natural Stonehave in common is they have passedthe test of time and still exist today,and are expected to last indefinitely.

Today these products are still widelyused around the world. New technologyhas allowed us to produce thinner pro d-ucts and better methods of attachment.Thin products means less weight andfaster installations that lead to lowe rcosts, and more flexibility with design.

Case Study – San Diego Ba l l p a rk( PE TCO ) (see Photo A & B) – So m eowners and architects have been re l u c-tant to specify Ceramic Tile, Stone orThin Brick for their projects because of

September 2004 v TileLetter 21

the perc e i ved risk. He re is a gre a texample of how substantiala d h e red veneers can be installed.Se veral years ago I was invo l ved ind e veloping the specification forthe exterior veneer at what was tobe the new San Diego Ba l l p a rkstadium. Architect AntoinePredock designed the stadiumand HOK Sp o rt was the pro j e c ta rchitect. The General Contrac-tor (GC) was a joint ve n t u recalled San Diego Ba l l p a rk Builders thatincluded Clark, Roel and Ba r n h a rt .HOK Sport said they wanted aCementitious Backer Unit (CBU) instal-lation for the 160,000 sq. ft. ofSandstone from India. The random size sof the stone ranged up to 24˝x24˝x5/8˝and would be installed as high as 130 feet

off the ground. We came up with a highp e rformance installation system prov i d-ing single source re s p o n s i b i l i t y. In Au g u s t2000 when Klaser Tile was negotiatingfor the contract to do the installation, Bi l lK l a s e r, myself and top-level re p re s e n t a-t i ves from the GC, HOK and the ow n e rmet at one of Klaser’s exterior ve n e e r

Photo A Photo B


p rojects to discuss the trade-off of CBUvs. Scratch-and-Brown Coat (SBC). T h es h o rt of it was that they wanted the moresubstantial SBC system. Klaser Tileended up being awarded the contract forthe installation and several mock-upswe re made to determine which SBC sys-tem would be used. Once that was decid-ed, a final mock-up was built per there q u i rements of Wiss, Ja n n e y, El s t n e rAssociates (WJE) engineers that wasstringently tested to make sure thatunder the most seve re seismic circ u m-stances the exterior veneer would not fail.

Testing – A full size mockup was builtby project subcontractors and was test-ed at Smith-Emery testing facility inLos Angeles per WJE’s procedures.

The conclusions of the testing werethat the stone facade assembly wasdesigned adequately for the substan-

tially designed wind and seismic loadsspecified for the San Diego Ballpark.Considering they took the testing tofailure exceeding 250% of design loadand racking +/-136 5.35 in. withoutany failure to the stone assembly says alot for how substantial adhered veneerscan and should be installed. (See Table 1 below for test results)

There were plenty of quality controlprocedures in place on the PETCOproject. For one thing the GC selectedKlaser Tile to do the installationbecause of his reputation for qualityand for the fact that Klaser Tile hadinstalled well over 3 million sq. ft ofexterior veneers in San Diego County.Unlike many installers, Klaser Ti l einstalls exterior veneers full time andusually has over 100 men working forthem at any one time. This specializa-tion was a big advantage for KlaserTile. Bill Klaser, the owner of Klaser

THE TESTS PERFORMED WERE:Thermal cycling test

ASTM E 331 water testingusing 10 psf (479-Pa) negative pressure

ASTM E 330 cyclic wind pressure testingto 100% design wind load

ASTM E 331 water testingagain using 10 psf (479-Pa) negative pres-sure

Racking test (+/-0.89 in. (23mm)to measure maximum movement in-plane

ASTM E 330 cyclic wind pressure testingto 150% design wind load

Racking test (+/-5.35 in. (136mm)to measure maximum movement in-plane

Wind pressure testing to failure

RESULTS:No Visible distress to stone or assembly

Water penetration only along top beamattributed to the incorrectly installed test-ing perimeter condition

No visible distress to stone or assembly

Water penetration only along top beamattributed to the incorrectly installed test-ing perimeter condition




Failure occurred at 87.5 psf (4.2kPa) negative pressure (250% of design load).Screws used to fasten the bottom track ofthe studs had sheared

Table 1


Tile, explained that the GC assignedsomeone during the day to randomlyselect freshly placed stones to havepulled off to make sure there was100% thin-set coverage. Klaser saidthat was in addition to his own qualitycontrol procedures that apply to all ofhis projects. Klaser installers will seteach stone and take it off to inspect theback for voids two or three times dur-

ing the installation process (see PhotoC). When Klaser was asked how thataffected his productivity, he said, “Firstof all, we can’t afford not to go throughthe process, because we are only going

to install it once. The other thing isthat unlike many installers my workforce installs exterior veneers full time,so they are trained specialists and havethe experience to install these stones ina systematic and safe method, whichmakes our company much more pro-ductive than other installers who don’thave the experienced work force.”

Klaser also said that he spends extramoney to buy a high perf o r m a n c emodified thin-set that provides close to500 psi shear bond strength, which hesays is “cheap insurance.” In addition,Klaser also ord e red the India Sa n d s t o n ebacks to be ground (see Photo D) t o

Photo C

Photo D


make it flatter and give it gro oved backsthat gives the back of the stone mores u rface area for bonding with a bettermechanical attachment. Klaser said thebiggest challenge on this job was thelogistics of moving the stone around tomake sure his workers didn’t have towait and we re continuously pro d u c t i ve .Klaser did say that one intere s t i n gp rocess they had to go through was for

the soffit applications; they had tocounter sink screws in the stone andthen plug them with stone cores theydrilled from other pieces of stone.Klaser said it really wasn’t necessarybecause the large stones have so muchsuction when they are installed theyd o n’t move and are ve ry difficult tore m ove when installed on a soffit. Hesaid it made the GC feel a lot betterk n owing that those 40-lb pieces ofstone we re mechanically attached. –EN D CA S E ST U DY

The key to the success of thePETCO Ballpark’s exterior veneer wasthe installation products and methods,and the quality control process. Thereare different installation methods tochoose from to achieve a quality instal-lation, but there are trade-offs, and inall cases it requires a substantial qualitycontrol process.

Methods of Ap p l i c a t i o n – there aremany methods of application for thinCeramic Tile, Stone and Brick. In allcases it is important that the stru c t u r a lf r a m ew o rk and the products are suit-able for the application. Eve ry applica-tion system has to be engineered forspecific factors such as weight, windload, backup material, structural flex-u re, seismic conditions, thermal andm o i s t u re movements and we a t h e rresistance. In addition, they mustalways meet all re q u i red building codes.

Uniform Building Code (UBC) andBuilding Officials and Code Adminis-trators (BOCA) set required perform-ance standards for these applications intheir Chapter 14 Exterior Wa l l


Covering sections, but local buildingdepartments make the final decisionand make exceptions. For instance,adhered veneer units must be less than1 5/8˝ thick, shall not exceed 36˝ inthe greatest dimension, nor be morethan 5 sf in total area, and shall notweigh more than 15 psf. An exceptionto these conditions is when the veneerweighs less than 3 psf. There are alsosome limitations to height dependingon the structural framew o rk. It isrequired to provide an attachment ofthe veneer that will withstand a mini-mum shearing stress of 50 psi. Units

larger than described will need to bemechanically attached and meet thoserespective codes.

There are also industry standardsthat need to be met for the productsand for their applications. For NaturalStone, the Marble Institute of America(MIA) publishes guidelines in theirDimension Stone Design Ma n u a l .They do call out ASTM standards withphysical requirements to qualify thesuitability of stone for various applica-tions. For instance, Granite DimensionStone used for exterior veneers mustmeet the ASTM C615-99 standard,

and they have other standardsfor each of the other cate-gories of stone such asLimestone, Marble, Sl a t e ,Tr a ve rtine, Serpentine, andQuartz-based stone. MIA alsostates that deflection in stoneapplications must not exceedL/720. For Ceramic Tile andfor modular stone tile thei n d u s t ry standards re vo l vearound the Tile Council ofNo rth America’s Ha n d b o o k(TCA), which prov i d e sacceptable installation meth-ods and details, and referencesANSI standards. TCA statesthat deflection in CeramicTile applications must notexceed L/360. The CeramicTile Institute of America(CTIOA) and the NationalTile Contractors Association(NTCA) also supports thesestandards and provide addi-tional guidelines. These stan-


dards and all appropriate performances t a n d a rds of the products must bespecified in the Quality Assurance sec-tion of the respective division (04400 –Stone; 09380 - Modular Stone Tile;09300 - Ceramic Tile).

Dimension St o n e is a natural buildingstone that has been cut and finished tospecifications and is usually 3/4˝ (2 cm)to 2˝ (5 cm) thick and several feet longand wide. 1 1/8˝ (3 cm) is the pre f e r re dthickness for exterior veneer applica-tions with a maximum facial surface of20 sq. ft. and weighs about 18 lbs psf.Mo d u l a r Stone Ti l e is generally less than3/4˝ (2 cm) thick and has a surface are aof up to 4 sf and is usually 1/2˝ (1.3cm) thick or less and weighs around 7p s f. Ce ramic Ti l e that is normally used

for exterior veneers is less than 1/2˝thick and weighs less than 5 psf. T h i nb r i c k has been used consistently ove rthe years and these applications try toemulate a full brick look, so their size swill normally be about 2-3/16˝x7-1/2˝in facial dimension and about 7/16˝thick weighing about 3 psf.

Mechanical Anchored Ve n e e r – T h e rea re various methods for mechanicallyanchoring larger units of stone( Dimension Stone). Anchors can bemechanical fasteners, continuous metale x t rusions, clips, dowels, or wire ties.Dimension Stone usually needs to be athickness of 3 cm (1 1/8˝) to accept themechanical anchors. Anchors are usedto support the weight of the stone


units, to resist live loading, and to allowthe adjustment of the position of theindividual units. Stone units can behandset installed or installed as pre f a b-ricated panels. In the past anchor meth-ods of attachment we re assumed to pro-vide a greater degree of safety thana d h e red methods, but at a considerablecost. But today with the improve dp roducts, methods, and contro l sa d h e red methods are considered as safe.

Exterior Ventilated Wall Sy s t e m s h a vebeen used in Eu rope for the past 30 ye a r sand is another mechanical attachmentmethod gaining some interest in theUSA. This method can be used withCeramic Tile as well as with Di m e n s i o nStone or Modular Stone Tile. It relies ona structural wall with an aluminumframe with ve rtical tubular studs secure dto the structural wall by means ofadjustable brackets. T h e re is a 2˝ to 2.4˝wide air space between the stru c t u r a lwall and the exterior veneer that pro-vides the ventilated system, which helpsmanage moisture and provides signifi-cant insulating related energy savings.

Adhered Veneer – Here again, therea re various methods for adheringveneer units. These methods applywhether it is Ceramic Tile, ModularStone Tile or Thin Brick. In some spe-cial cases there are products and meth-ods for adhering Dimension St o n eunits. Generally speaking, the samemethods apply whether you create pre-fabricated panels to install, or the indi-vidual units are installed in place. Thetypical substrates used for attaching theveneer units to a structural wall, with


the re s p e c t i ve appropriate stru c t u r a lframework in place, are concrete blockmasonry units (CMU), cast-in-placeconcrete walls, pre-cast concrete walls,p re-fabricated wall panels, concre t es c r a t c h - a n d - b rown coat (SBC), andcementitious backer unit (CBU ) .There are some applications that usesilicone to attach the tile or brick unitsto a corrugated metal, which will notbe covered in this article.

All of these different sub-surf a c e sneed to be properly pre p a red to somed e g ree. This is a key process and makesa big difference to the outcome of theinstallation. The surfaces must besound, dimensionally stable, clean, andf ree of curing compounds and othercontaminates. The wall must be plumband the surface variation must not

e xceed 1/4˝ in 10´-0˝. It is possible tobond directly to CMU, cast-in-placewalls, and pre-cast walls if they aresound and properly pre p a red. It is re c-ommended howe ve r, to apply a SBCfirst with a proper type and pro p e r l yplaced moisture barrier. W h e ninstalling over structural metal studsthe SBC method is pre f e r red, but theC BU method is legitimate. When usingthe CBU method the veneer units arenormally bonded directly to it, but willre q u i re proper preparation. It is re c o m-mended to first attach sheathing to thestuds for added dimensional stabilityand to form a barrier for the building.The proper type moisture barrier isplaced considering the climatic condi-tions of the geographic area, and thenthe CBU is attached.

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CBU applications are considered alighter and less expensive installationsystem, but there are trade-offs that canbe compensated for, if properly man-aged. To name one, the CBU surface isonly going to be as plumb and consis-tent as the studs to which it is applied.Generally there is a lot of variation inthe CBU surface, which can be mini-mized to a degree by filling low areaswith the polymer modified or latexmodified thin-set adhesive being usedto set the veneer units. Often this stepis left out when stone that is irregularin its thickness and surface is used,because irregularity is expected withinreason. With a SBC, the installers caneasily compensate for any irregularitiesin the studs and achieve a plumb sur-face. Another trade-off is that there are

many joints between the sheets of theCBU. The 3´x5´x1/2˝ is a commonCBU size, but many times 4´x8´x1/2˝sheets are used on exterior ve n e e r sbecause they line up better with thestuds and have fewer joints to contendwith. The CBU sheets should beinstalled staggered-joint with those ofadjacent rows and any underlyingmaterials to minimize movement, andthe joints should be filled and tapedwith a 2˝ fiberglass fiber mesh tape. Attimes, a special liquid or trowel appliedwaterproof membrane is applied ontop of the CBU for added moistureprotection and to minimize potentialefflorescence problems. With a SBC,the installers don’t have to contendwith this problem, and they have amuch more structurally sound surface.

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The method of installation of theCeramic Tile, Modular Stone Tile andThin Brick (thin veneers) over these va r-ious substrates is ve ry similar, with somee xceptions. T h e re are various differe n c e sin the veneer products that have to betaken into account. Ceramic Tile tendsto be ve ry consistent in sizing and won’tneed its surface sealed if the surface hasa fired glazed surface. Stone, on the

other hand, can be ve ry consistent insizing or may be ve ry inconsistent inthickness, facial sizing and warpage.Normally the stone surface needs to besealed, particularly if it is high absorbingand not a dense polished stone. T h i nBrick can va ry significantly in sizing andwarpage and those differences must beaccounted for and expected. Thin Br i c kcan be ve ry dense, but normally it ism o re porous and re q u i res sealing afterthe installation. Ef f l o rescence comingt h rough grout joints or the porous sur-faces can be minimized by using sealersand by applying waterproof membraneson the substrate before attaching thethin veneer to it.

Quality Assurance and Qu a l i t yC o n t ro l – No matter which method ofapplication is used, the most import a n tp a rt of a project is having adequatequality assurance and quality contro lspecifications, specific to that pro j e c t .Often these sections of the specificationa re cut-and-paste and left up to the sub-contractor to implement himself, whichcan be a mistake. If done corre c t l y, thesesections are critical to the success of thep roject re g a rdless of the method ofapplication. For this article I will re v i ewthe key quality assurance and qualityc o n t rol steps for both the scratch-and-b rown coat (SBC) and for the cementi-tious backer units (CBU). I’ve chosen tofocus on these methods because they arem o re conducive for installing CeramicTile, Thin Brick and Modular St o n eTile. These methods are also considere dm o re affordable, and I think they arethe least understood.


S c r a t c h - a n d - Brown Coat (SBC) ( p e rTCA method W241-03 – see Dra w i n gW 2 4 1 ) - The SBC is the pre f e r re dmethod, and considered the bestmethod, for an exterior ve n e e r. It is amuch more substantial application andt h e re is much more control over achiev-ing a quality finished product. For larg-er projects it is much more practical toh a ve the lath and plaster trade installingthe SBC. They use pumps to apply thecement base coats, which allow them toinstall faster and less expensive l y. T h ep roblem is they normally work withs t a n d a rds for their own trade that are farless than what is necessary for theCeramic Tile and Stone trade. Fl a t n e s sfor Po rtland cement is 1/4˝ in five feetfor the plastere r’s brown coat, and in theceramic tile industry is 1/4˝ in ten feet.

Moisture Barrier – Moisture barriersshould be specified by the pro j e c tarchitect. The correct type of mem-brane needs to be specified and it needsto be properly placed taking climatic


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conditions and wall configurationsinto consideration. Lathers typicallyuse asphalt saturated Kraft paper, gradeD (breathable) or B (vapor barrier), top rotect the building interiors fro mmoisture intrusion. The Tile Industrynormally calls out 15 lb. asphalt satu-rated felt or 4 mil polyethylene film asthey do for shower applications. TheTechnical Services Information Bureau(TSIB) recommends applying thepaper and lath in two separate applica-tions. When using paper that isattached to the expanded-metal lath(paper-back lath) a few problems canoccur. One is the improper lapping ofthe lath sandwiching the paper. Thereshould be no paper between the twolapping pieces of lath because it canlead to cracking. Two, the paper-

backed lath tends to get tears from theedge of the lath during its handling.All horizontal and sloped surfaces mustbe waterproofed. There are bituminousmembranes that are waterproof andwill seal penetrations when attachingthe metal lath or there are waterproofmembranes that can be applied overthe surface of the substrate for theveneer to be attached.

Fl a s h i n g – Water intrusion is a bigp roblem and key to managing moistureis to properly flash transition areas anda l l ow moisture to escape. Outside cor-ners, inside corners, parapets, bottomwall flashing and weeps, window s i l l s ,and movement joints all need some sortof flashing. Flashings are normallyformed from galva n i zed sheet metal,


bituminous membranes or a combina-tion of the two. Flashings should belapped and sealed, and should be con-tinuous around inside and outside cor-ners. Ho r i zontal surfaces such as win-d owsills, ledges, copings, caps, and anyh o r i zontal member should be wrappedwith a membrane and the surface of themembrane should slope away from thebuilding. Another important detail isthe foundation weep screed at the wallbase. Mo i s t u re will travel into thecement grout joints through thecement thin-set adhesive and the mor-tar substrate. With the help of gravity,e xcess moisture has an escape ro u t et h rough the we e p s .

Movement Jo i n t s – Per TCA EJ171-03 Movement Joints (formerly expan-

sion joints) should be placed eve ry 8´ to12´ in each direction. They should alsobe located at all change of planes toinclude all inside and outside corners.Both the veneers and their substrateswill move to some degree from thermoand moisture movements, and fro mother dynamic forces such as windloads. It is the differential in the move-ments from the different materials thatcompound the issue and make this ani m p o rtant step. The minimum widthof the movement joint is 1/2˝ for joints16´ on center, but there are other fac-tors to consider, for instance the mini-mum widths must be increased 1/16˝for each 15º F tile surface temperaturechange greater than 100º F betwe e nsummer high and winter low. It is theresponsibility of the project engineer to


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k n ow what type and where to placem ovement joints, as it is not within thei n s t a l l e r’s qualification to determinetheir exact locations or type.

The ideal movement joint for thinveneer is a two-piece #40 metaladjustable screed, which needs inde-pendent framing for its attachment.The lathers normally want to use a #15control joint, which limits the move-ment, and doesn’t require the inde-pendent framing. The two-piece typecan accommodate movements of con-traction, expansion and shear stresses.

Sealants – This is a very importantissue. The correct sealant needs to beused and installed correctly to get thefull potential out of the movementjoints. Not only do the sealants need to

accommodate the movements, but alsothey have to keep moisture out andweather the local climatic conditions.The correct sealant must be selected bythe architect to ensure compatibilitywith the different products it will be incontact with for maximum adhesionand durability considering the variousconditions. Generally speaking, ure-thane and 100% structural siliconesealants are used for exterior applica-tions. Use of backer rods is critical togetting the full performance from thesealant. Backer rod prevents the sealantfrom adhering to the bottom of thejoint and keeps it thin enough toaccommodate maximum move m e n twithin the joint. Joints should becleaned and have a primer appliedprior to filling. Tooling of the joint


should be prescribed to facilitatedrainage in the joint and prevent anymoisture collection.

Metal Lath – Not only is using thecorrect type of metal lath for reinforce-ment of the SBC necessary, but alsomost important is how it is attached.3.4 lb/sq.yd. self-furring galva n i ze ddiamond-mesh lath is recommendedfor exterior veneers according toCTIOA. Whether it has the moisturebarrier paper attached or not isn’timportant, as long as the paper doesn’tget punctured. Making sure it is lappeda minimum of 2 inches metal to metaland paper-to-paper is important. Lathshould be attached with screws or sta-ples that will penetrate into woodframing, not less than 5/8˝, and

through metal supports adaptable forscrew attachment not less than threethread turns. Screws should be placedevery 6 inches vertically and horizon-tally along the studs. Screw penetra-tions through the moisture barrier areconsidered sealed when under com-pression for the vertical surface, but allsloped and horizontal surfaces must befully waterproofed. Whether moisturebarrier paper is attached to the lath ornot is not important, provided thepaper does not get punctured.

Plumb and Flat Wall – One of thebiggest challenges for the installer isgetting the plasterer to understand thatthey need a finished substrate wall sur-face that is plumb and that the surfacevariation must not exceed 1/4˝ in 10´-


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0˝. That amount of variation is reason-able for the installer to compensate forduring their installation to achieve anacceptable flat veneer surface, butbeyond that variation there are trade-offs that will cost the installer in pro-ductivity and jeopard i ze the ove r a l lquality of the installation. The tech-niques the tile and stone installer use toapply the SBC makes it easy for themto achieve a nice plumb surface becausethe mortar will easily compensate forirregularities in the studs and sheath-ing. The plasterer doesn’t screed off thesame way because it is faster and it isn’tnecessary when they know they cancompensate for the irregularities intheir final plaster coat. So for tile andstone veneer you have to have a plumbbrown coat and it is much easier, lessexpensive, and safer to do it right thefirst time. Often the plasterer has tocome back at his expense to patch thebrown coat that can cause additionalproblems if not done correctly.

Cementitious Backer Units (CBU)(per TCA method W244-03 – seeDrawing W244) - The CBU is a legiti-mate substrate and method for apply-ing Ceramic Tile, Modular Stone Tile,and Thin Brick, but with the previous-ly mentioned trade-offs. Here too, forlarger projects it is much more practi-cal to have the lath trade (lathers)install the CBU in preparation for theinstallation of the thin veneer becausethey can do it faster and for less cost.Again it is very important that thereare adequate specifications and qualitycontrols to ensure a quality installa-


tion. Not all cementitious backer unitsare recommended for exterior applica-tions. It is important to get manufac-t u re r s’ recommendations and war-ranties for these applications, and tofollow their installation instructions.

Moisture Barrier – Moisture barriersare required and must be specified fortype and placement by project engi-neers. It is recommended to havesheathing over the studs to provideadded stability and to minimize sag-ging between studs. All horizontal andsloped surfaces must be waterproofed.There are bituminous membranes thatare waterproof and will seal penetra-tions when attaching the metal lath, ort h e re are special waterproof mem-branes that can be applied over the sur-face of the substrate that the veneer canthen be attached.

Flashing – Flashing must be incorpo-rated into the installation as describedin the SBC section above.

Movement Joints-Sealants - Sealantsmust be incorporated into the installa-tion as described in the SBC sectionabove.

Attachment – Attachment is a criticalstage of the installation. As describedabove, CBU sheets must be placedstaggering joints with those of adjacentrows and those of the underlying sub-strate. The CBU should be fastened onframing every 8˝ o.c. with perimeterfasteners at least 3/8˝ and less than5/8˝ from ends and edges. Fastenersmust be corrosion-resistant steel screws1-1/4˝ long for 1/2˝ thick CBU .Different CBU products will ask fordifferent spacing between sheets. Jointsshould be filled with a modified thin-set mortar and taped with a 2˝ alkali-resistant fiberglass mesh tape. Specialattention should be paid to lippagebetween the edges of the CBU. Theseedges should match up in height andmake a smooth transition.

Plumb and Flat Wall – It is difficult toget a finished CBU substrate wall sur-face that is plumb and that the surfacevariation will not exceed 1/4˝ in 10´-0˝. That is one of the trade-offs ofusing CBU method versus the SBCmethod as mentioned earlier.

Thin-set Adhering – Whether it is theSBC method or the CBU method, acritical step is adhering the tile, stoneor brick to the finished substrate sur-face. The process is the same for eithermethod. The adhesion to the substrateis just as important as it is to the back


of the veneer. It is rare tohave a cohesive failure in thethin-set adhesive. Normallyif there is a problem it isbecause one side or theother failed to adhere. Boththe substrate and the backof the veneer have to beclean and free of any type ofcontaminate which couldact as a bond-breaker. Theadhesive has to come in fullcontact with both surfaces.It is recommended to forcefully scrapea thin coat of the thin-set to both sur-faces during the installation process,making sure it remains tacky when thethin-set for setting is applied. T h eANSI standards say there can be no lessthan 95% coverage on the back of thetile, but there should be no vo i d sbehind the tile that can lead to pocketsthat collect moisture and contribute toefflorescence, or can expand causingother problems in colder regions. Sincemost of the installations today aregoing in with larger module tiles andstones (tile) it is critical to make sureenough thin-set is applied. Air can gettrapped in the back as the tile is placedand it has no way of escaping. NTCArecommends a troweling method totrowel the thin-set in one direction andset and move the tile perpendicular tothat direction to allow air to escape.Large stone tiles require applying asubstantial amount of thin-set to bothsurfaces and setting, which may requirepulling the piece off during thatprocess to ensure full coverage. Thereare limitations on how thick the thin-

set application can be depending onthe type thin-set, so check with thethin-set manufacturer. Photo E is anexample of an installer who used a big3/4˝ marble loop trowel to apply thethin-set to the wall, but it wasn’tenough to compensate for the wall notbeing plumb. Note there was no con-tact to the back of the tile; it was beingheld in by grout alone with gravityworking against it! This is where aquality control plan has to be in placeto make sure the tiles are getting fullc overage. A third party inspectorshould randomly have freshly set tilespulled for inspection (that way theycan be reused with minimum effort).If one tile is pulled in an area and itdoesn’t have full coverage, then 3 moreare pulled. If one or more of thosedon’t have full coverage then that sec-tion of work should be removed andreplaced.

Another potential problem is havingthe thin-set dry too quickly before itcan achieve an adequate bond. Thiscan be caused by a combination ofcompounding issues that include hot

Photo E


and windy weather, high absorbing tileand substrate, applying the thin-set toosoon to substrate and letting it skinover before the tile is applied. Climaticconditions can affect the installationproducts, so product limitations mustbe noted and provisions must be madefor protection and adjustments. Covermust be provided for the installation asneeded during high and low tempera-tures and to shield from rain.

Thin-set Ad h e s i ve: It is re q u i red top rovide an attachment of the ve n e e rthat will withstand a minimum shear-ing stress of 50 psi. But when you con-sider all the various potential pro b l e m swith uncontrollable climatic conditionsand imperfect job site conditions andwith portions of a labor force that maynot be perfect, then you should beusing the best products available, andnot just meet the minimum re q u i re-ment. CTIOA recommends that apolymer modified thin-set or latexmodified set (modified thin-sets) beused for exterior veneers that meets aminimum of 325 psi shear bonds t rength to porcelain tile per ANSI118-4-1999 F-5-2-4. Po rcelain tile isthe standard because it is ve ry denseand impervious, which makes it one ofthe most difficult materials to bond.The modified thin-sets come with dif-f e rent levels of quality and that is whythe CTIOA calls out the perf o r m a n c el e vel. Quality modified thin-sets pro-vide better adhesion, better tack, betteropen time, and other better perf o r m-ance characteristics that help pre ve n tsome of the mentioned pro b l e m s .

Grouting Tile Joints – On the largerDimension Stone installations a sealantto fill the joints between the stones willbe used which keeps moisture fromgoing through the grout joints andprovides another level of movementcontrol. Otherwise, the cementitiousgrout should be a lower absorbing andbetter adhering polymer modifiedgrout or a latex modified grout (modi-fied grouts) meeting ANSI 118.7. Theporous veneers should be sealed priorto grouting to aid in grouting clean up,but the edges of the veneer have to beleft unsealed. Regardless whether thegrout is bagged and tooled in the joint,or troweled in the joint, it needs to bewell compacted and shaped to facilitatedrainage in the joint and prevent anymoisture collection. It is recommendedto seal the clean tile and grout surfaceafter the installation for maximumprotection.

Su m m a ry – The results of the testingdone on the PE TCO Ba l l p a rk’s stoneveneer is a great testament to how sub-stantial and safe ceramic tile, naturalstone, and thin brick can be as ana d h e red ve n e e r. The key to a long lastinginstallation is having a clear and corre c ta rchitectural specification to include ap roject specific quality assurance andquality control section. The quality con-t rol plan should not be left up to thesubcontractor to implement, but rathera third party should be assigned. Wi t hthis type of quality assurance, risk isg reatly diminished, and that will lead tom o re owners and architects specifyingceramic tile, stone or thin brick for their


p rojects. When you consider the savingsin cost and time with these methods,t h e re should be a lot more business outt h e re for our installers, manufacture r s ,and distributors. As in all things in lifet h e re are trade-offs. Yet if you use any ofthe legitimate methods corre c t l y, andp rovide adequate quality controls, wecan have a building that can potentiallylast for centuries to make a future state-ment of design and quality integrity asour legacy.

Additional Information:Au t h o rCe ramic Tile Consultant, Donato Pompo CTC CSICDT MBA is the founder of Ce ramic Tile and St o n eConsultants (CTaSC). Donato has over 25 ye a r sexperience in the Ce ramic Tile and stone industryf rom installation to distribution, to manufacturing

of installation products. CTaSC provides services inQuality Control Se rvices for products and installa-tion methods to include writing specifications, Jo bProblem In vestigations, Training Pro g rams to includeonline courses from his new Un i versity of Ce ra m i cTile and Stone (UofCTS) campus, Ma rket Re s e a rc hand Ou t s o u rcing Se rvices and Business Pl a n n i n gs e rvices. You can reach Donato by visiting his web siteat www.CTaSC.com, or e-mail at Donato@C TaSC.com, or by calling 619-669-2967.

Re f e re n c e sMarble Institute of America (MIA) DimensionStone Manual; Tile Council of America (TC A )Handbook for Ce ramic Tile Installation; Ce ra m i cTile Institute of America (CTIOA) field re p o rt s ;National Tile Contractors Association (NTC A )Re f e rence Manual; Technical Se rvices In f o rm a t i o nBu reau (TSIB); American National St a n d a rdSpecifications for the Installation of Ce ramic Ti l e(ANSI); Un i f o rm Building Code (UBC); Bu i l d i n gOfficials and Code Ad m i n i s t rators (BOCA); W J ESan Diego Ba l l p a rk project Testing Re p o rt.

Training • Marketing Services • Business Planning

Job Problem Inve st i gation • Te sting Serv i c e s

All Services Customized for YouFor Special Ad Discount enter Coupon Code: A D T L 2 0 0 4

Visit our website at w w w. C Ta S C . c o m

Phone (619) 669-2967Fax (619) 669-2968

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• U n ive rsity of Ceramic Tile and Stone (UofCTS) OnlineE d u c ational Courses – Te chnical and Sales Oriented Cours e s

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