On graveled surfaces, all loose gravel and debris shall be removed by power brooming or vacuuming. All blisters shall be removed and sealed or cut, fastened down and sealed. Any accumulation of bitumen or other irregularities shall be scratched and removed so as to produce a smooth surface.
On smooth surfaced roofs, the surface must be clean and dry. All blisters shall be removed and sealed or cut, fastened down and sealed. For Type III hot asphalt attachment of new insulation board, priming of the old roof surface after preparation is necessary.
Coal-tar pitch or heavily resaturated roofs may require removal. Contact Sarnafil Technical for coal-tar pitch or heavily resaturated reroof preparation requirements.
A dry, clean and smooth substrate shall be prepared to receive the Sarnafil Sarnafast mechanically-attached roof system.
The Applicator shall inspect the substrate for defects such as excessive surface roughness, contamination, structural inadequacy, or any other condition that will adversely affect the quality of work.
All roof surfaces shall be free of water, ice and snow.
Sarnafil shall be applied over compatible and accepted substrates only.
VAPOR RETARDER/AIR RETARDER INSTALLATION General Criteria:
Interior (inside temperature/relative humidity) and/or exterior conditions may create a need for a vapor retarder. The design professional shall, based upon information supplied by the owner, decide whether a vapor retarder is necessary. It is the design professional's responsibility to determine the type and location of a vapor retarder. If sealed properly, a vapor retarder can also act as an air retarder (positive pressure) for roofs intended over air-permeable decks (steel, wood, precast, etc.). When reroofing over the existing asphalt roof, the old roof may be considered to be an adequate vapor retarder/air retarder if the details are properly sealed.
New Construction or Reroofing with Removal of Existing Roofing
Steel Deck or Wood Deck:
For vapor drive leaving the building, the vapor retarder shall be laid directly over the deck or on a support board with all side and end joints sealed in accordance with the manufacturer’s instructions. The vapor retarder shall be sealed to all penetrations and terminations. The vapor retarder may be loosely laid or adhered with an adhesive supplied or recommended by the same manufacturer. The insulation or recover board must be mechanically fastened in this case.
Poured Structural or Precast/Prestressed Concrete Decks:
Conduct moisture and adhesion tests in accordance with industry guidelines. If test requirements are met, prime the deck with asphalt primer, let dry and then adhere a base sheet with full mopping of Type III hot asphalt at a minimum rate of 25 lbs. per 100 square feet (1.2 kg/m²). Install a second ply in the same manner and then seal with an asphalt glaze coat. The base sheet and asphalt shall be installed in accordance with the manufacturer's instructions. The new insulation board shall be attached with additional Type III hot asphalt or by mechanical fasteners to the roof deck.
WOOD NAILER INSTALLATION
Install continuous wood nailers at the perimeter of the entire roof and around roof projections and penetrations as shown on the Detail Drawings.
Nailers shall be anchored to resist a minimum force of 300 pounds per lineal foot (4,500 Newtons/lineal meter) in any direction. Individual nailer lengths shall not be less than 3 feet (0.9 meter) long. Nailer fastener spacing shall be at 12 inches (0.3 m) on center or 16 inches (0.4 m) on center if necessary to match the structural framing. Fasteners shall be staggered 1/3 the nailer width and installed within 6 inches (0.15 m) of each end. Two fasteners shall be installed at ends of nailer lengths. Nailer attachment shall meet this requirement and that of the current Factory Mutual Loss Prevention Data Sheet 1-49.
Thickness shall be as required to match substrate or insulation height to allow a smooth transition.
Any existing nailer woodwork which is to remain shall be firmly anchored in place to resist a minimum force of 300 pounds per lineal foot (4,500 Newtons/lineal meter) in any direction and shall be free of rot, excess moisture or deterioration. Only woodwork shown to be reused in Detail Drawings shall be left in place. All other nailer woodwork shall be removed.
INSULATION INSTALLATION General Criteria:
Insulation shall be installed according to insulation manufacturer's instructions.
Insulation shall be neatly cut to fit around penetrations and projections.
Install tapered insulation in accordance with insulation manufacturer's shop drawings.
Install tapered insulation around drains creating a drain sump.
Do not install more insulation board than can be covered with Sarnafil membrane by the end of the day or the onset of inclement weather.
Use at least 2 layers of insulation when the total insulation thickness exceeds 2-1/2 inches (64 mm). Stagger joints at least 12 inches (0.3 m) between layers.