Plywood or Oriented Strand Board
New 18mm exterior grade plywood fixed in accordance with the current standards ensuring it is of adequate rigidity for the joist spans involved and fixed with corrosion resistant ring shanked nails or screws at 150mm centres to the perimeter of the panels and 300mm along the intermediate supports. Fixings should be well driven to avoid damage to the membrane.
Good roofing practice requires the roof to be free of significant ponding within 48 hours of rainfall. Where the structural deck does not provide drainage or removal of standing water within 48 hours, the substrate should be corrected to provide positive drainage.
It is recommended that all decks in a warm roof construction be sealed prior to installing the roofing system to prevent air infiltration beneath the membrane. Sealing the deck is accomplished by installing a vapour control layer over the deck and sealing around all penetrations.