b'NRCA continues to recommend roof system designers use caution when specifying the installation of membrane roof systems over newly poured normal-weight and lightweight structural concrete roof decks.Protective Roofing Safety Productsments and make that information available to specifiers. The vapor drive conditioning used in this testing is one possible as-sessment method. BYNRCA continues to recommend roof system designers use caution when specifying the installation of membrane roof sys-tems over newly poured normal-weight and lightweight struc-tural concrete roof decks. When adequate dryness of concrete roof decks cannot be reasonably ensured, NRCA recommends a well-adhered, low-perm-rated vapor retarder be specified for installation directly over the concrete roof deck. Then, an ad-hered or loosely laid ballasted roof system can be specified over the vapor retarder, preferably installed the same day or within several days of vapor retarder installation.Roof system types that involve mechanical fasteners that would penetrate the vapor retarder should be avoided to ensure vapor retarder performance. The purpose of the vapor retarderThe PR 100 Guardrail Systemis to isolate a concrete decks free water within the concrete andis an efficient and practical perimeter guardrail that allows youminimize the potential for moisture vapor transport into theto work right to the edge of the roof.roof system.Meets and exceeds OSHA & WCB requirementsNRCA also maintains its long-standing recommendation Accommodates: parapets and cant stripsEasy to installthat the use of curing and finishing compounds be avoided Provides unobstructed access to roof edgewhen placing and finishing structural concrete roof decks as these compounds are known to retard moisture release and can affect adhesion of roofing materials.In addition, NRCA suggests roof system designers mini-mize the use of materials and products with organic content over concrete roof decks to decrease the potential for micro-bial growth in the event moisture from a concrete roof deck infiltrates the roof system. Examples of roofing products with organic content include fiberglass-reinforced, cellulosic mat-faced polyisocyanurate; perlite board; and wood fiberboard. Coated, fiberglass mat-faced polyisocyanurate insulation is pre- The PR 600 Mobile Fall Protection Systemferred over fiberglass-reinforced, cellulosic mat-faced polyisocy-anurate in concrete roof deck applications. can be moved along the roof by pulling the cart to the desired working location, For reroofing situations over existing concrete roof decksproviding a safe working area. The PR 600 meets O.S.H.A. compliance 1926.502D.where there is evidence of concrete deck-related moisture prob-lems, NRCA suggests roof system designs similar to those rec- Roofing & Sheet Metal Super Service Centresommended for newly placed concrete roof decks.Additional information about moisture migration in roofEDMONTON, AB CALGARY, AB WINNIPEG, MB WESTON, ONassemblies is provided in the Condensation and Air Leakage(780) 432-2786 (403) 255-8236 (204) 338-7613 (Weston Road)Control section of The NRCA Roofing Manual: Architectur- BARRIE, ON HAMILTON, ON TORONTO, ON (416) 745-4111al Metal Flashing and Condensation and Air Leakage Control.(705) 792-6683 (905) 560-2858 (416) 534-8421 WESTON, ONAdditional information about concrete roof decks and vaporOAKVILLE, ON PICKERING, ON LONDON, ON (Signet Drive)retarders is provided in Chapter 2Roof Decks and Chapter 3(905) 825-0034 (905) 426-4443 (519) 668-3626 (416) 744-2050 Air and Vapor Retarders, respectively, of The NRCA Roof-ing Manual: Membrane Roof Systems. www.sparmarathon.caMark S. Graham is NRCAs vice president of technical services.ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 2 202323'