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ROOF 1 1 1 'A GNS —Address drainage deficiencies to provide positive drainage, Pre-cast Concrete Decks —Remove and replace all wet roofing materials; —These decks are usually manufactured as planks or slabs and —Concentrate on thorough surface preparation. constructed of steel-reinforced Portland cement and solid aggregate;often they are made with hollow cores to minimize their weight. Re-covering Over Coal Tar Pitch Roofing —All deformed panels must be replaced. Coal tar pitch has oils and vapors that can be harmful to various —joints must be filled with a masonry grout to correct roofing membranes and may discolor white thermoplastic imperfections between slabs and feathered to provide a slope not membranes.Coal tar pitch may also"cold flow"through fastener greater than'/8:12 for adhered insulated assemblies. holes into the building.For these reasons,GAF does not recommend —If the joints cannot be grouted and finished smooth,then a re-covering over existing coal tar pitch roofs. leveling course of lightweight insulating concrete(minimum 2" [51 mm]thickness)must be applied.Do not seal joints ROOF DECKS between the slabs;leave open to permit venting and drying of the roof fill from below. It is the responsibility of the engineer,architect building owner,or roofing contractor to determine the fitness of a deck for a specific roofing stem installation. Pre-stressed Concrete Decks Additionally,GAF is not responsible for moisture-related problems associated with any deck materials. —GAF recommends a minimum 2"(51 mm)cellular lightweight concrete fill be installed over all pre-stressed concrete decks Most common structural roof deck types are suitable substrates for prior to installation of the roof system and/or insulation the installation of an EverGuard®roofing system. because variations in camber and thickness of pre-stressed concrete members may make securement of the roof system Structural Steel difficult. —Min.22 gauge(standard FM-approved steel decking is 22 gauge —Provisions must be made for the curing or drying of the fill g g pP g g g installed over the top of the pre-stressed deck members.Do not in thickness). seal joints between the slabs/leave open to permit venting and —24-26 gauge decks require a GAF Field Services Manager's or drying of the roof fill from below. Director's approval.Thinner-gauge steel decks usually require additional mechanical fasteners to achieve comparable roof attachment performance. Poured Structural Concrete Decks —18 gauge,20 gauge,and 22 gauge Grade E high-strength steel —Should be properly cured prior to application of the roofing decks usually require fewer mechanical fasteners to achieve system;twenty-eight(28)days is normally required for proper comparable roof attachment performance. curing.Check curing agents for compatibility with roofing materials.Prior to the installation of the roof assemblies,GAF recommends the evaluation of surface moisture and deck's Structural Concrete dryness through the use of ASTM D4263 or a hot bitumen test. —Minimum 2,500 psi(17,237 kPa)compressive strength. —Should be poured over removable forms or must provide for —Min.2" (51 mm)thickness(pre cast),min.4" (102 mm) bottom side drying.Poured-in-place structural concrete decks that are poured over non-vented metal decks or pans that thickness(poured-in-place). remain in place can trap moisture in the deck under the roof —Cannot be wet or frozen.If the deck is determined to be wet,it system. must be allowed to dry. —The underside of the concrete decks,either the vented metal —For insulated decks,wood nailers of equivalent thickness to the forms or exposed concrete,should remain unobstructed to roof insulation must be provided at perimeters and projection allow the escape of water vapor.Materials that retard the flow openings to act as an insulation stop and to provide for the of vapor should not be installed directly below the deck.Foil- nailing of the flanges of metal flashing. faced insulation secured to the bottom of the deck,spray-on —Ridges and other irregularities require grinding to provide a fireproofing,or paint,which obstruct the venting of the smooth and even substrate surface. concrete,are just three examples of things that can trap moisture in the concrete deck below the roof —For non-insulated decks,nailers must be flush with deck —GAF recommends that a vapor retarder be used directly over any surfaces. poured structural concrete installed over non-removable form —When applying insulation directly to the deck in hot asphalt, decks or any impermeable substrate and requires the use of prime with asphalt/concrete primer,meeting ASTM D41,at a a vapor retarder for lightweight aggregate structural concrete rate of 1 gal/square(4.08 L/10 ml)and allow the primer to dry decks in this configuration. prior to the application of the roofing system. —Roofing professionals must take care with lightweight structural concrete decks The selection of the deck material and its suitability for use is the responsibility of the designer of record, who must make appropriate design accommodations to address high moisture content encountered in lightweight structural concrete.GAF is not responsible for moisture-related problems associated with any deck materials. 12