b'cific concrete mix designs curingcan be used for other roof deckofvaporretarderinstallation.moisturefromaconcreterooftural concrete roof decks present and moisture release rates. It alsotypes. Broader roof deck criteriaRoofsystemtypesthatinvolvedeckinfiltratesintotheroofunique moisture migration prob-may be useful for these partiesplacesadditional,unreasonablemechanicalfastenersthatwouldsystem.Examplesofroofinglems and potential liability for the to consult the buildings projectliability on roofing contractors;penetratethevaporretarderproductswithorganiccontentroofing industry. You should take or roof system designer and thearoofingcontractormayhaveshould be avoided to reasonablyincludefiberglass-reinforced,special care to not assume respon-roof system manufacturer. onlylimitedknowledgeofandensurevaporretarderperfor- cellulosicmat-facedpolyisocy- sibility and liability for moisture NRCAs premise and positioncontroloveraspectsofaroofmance. The purpose of the vaporanurate; perlite board; and woodin normal-weight structural con-isconsistentwiththeflooringdeck and building structure. retarder is to isolate the concretefiberboard.Coated,fiberglasscreteandlightweightstructural industry.ForresilienttileandNRCArecommendsroofdecks free water within the con- mat-faced polyisocyanurate insu-textile floor coverings and coat- systemdesignersusecautioncrete and minimize the potentiallation is preferred over fiberglass- concrete decks.ings, floor covering manufactur- when specifying the installationfor moisture vapor transport intoreinforced, cellulosicmat-facedAdditional information about ers generally require quantitativeof membrane roof systems overthe roof system. polyisocyanurateinconcretemoisture migration in roof assem-moisturetestingbeperformednewlypourednormal-weightNRCA also maintains its long- roof deck applications. blies is provided in the Conden-beforefloorcoveringinstalla- andlightweightstructuralcon- standingrecommendationtheFor reroofing situations oversation and Air Leakage Control tion on concrete. ASTM F2170,crete roof decks. When adequateuse of curing and finishing com- existingconcreteroofdeckssection of The NRCA Roofing Standard Test Method for De- drynessofconcreteroofdeckspounds be avoided in placing andwhere there is evidence of con- Manual:ArchitecturalMetal termining Relative Humidity incannotbereasonablyensured,finishing structural concrete roofcretedeck-relatedmoistureFlashing and Condensation and ConcreteFloorSlabsUsinginNRCArecommendsawell- decks as these are known to retardproblems, NRCA suggests roofAir Leakage Control. Additional situProbes,oftenisusedforadhered,low-perm-ratedvapormoisturereleaseandcanaffectsystem designs similar to thoseinformation about concrete roof this purpose. retarderbespecifiedforinstal- adhesionofroofingmaterials.recommended for newly placeddecks and vapor retarders is pro-NRCAalsorecommendslation directly over the concreteAlso, NRCA suggests roof systemconcrete roof decks. vided in Chapter 2Roof Decks roofingcontractorslimittheirroof deck. Then, an adhered ordesignersminimizetheuseof acceptanceofconcreteroofloosely laid ballasted roof systemmaterialsandproductswithor- and Chapter 3Air and Vapor decks to the top surface of thecan be specified over the vaporganic content over concrete roofClosing Thoughts Retarders,respectively,ofThe roof deck being visually dry andretarder, preferably installed thedecks to minimize the potentialCurrently, newly poured and,NRCARoofingManual:Mem-broom clean. These criteria alsosame day or within several daysfor microbial growth in the eventin some instances, existing struc- brane Roof Systems.ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 1 202215'