Roof sheathing and sheathing supports of wood are also permitted in noncombustable buildings provided:
- They are installed above a concrete deck.
- The concealed space does not extend more than 1m above the deck not less than 50 mm thick.
- The concealed roof space is compartmented by firestops.
- Openings through the concrete deck are located in noncombustible shafts.
- Parapets are provided at the deck perimeter extending at least 150mm above the sheathing.
- No building services are located on the roof other than those placed in noncombustable shafts.
The noncombustible parapets and shafts are required to prevent roof materials igniting from flames projecting from openings in the building face or roof deck.
In buildings that must be of noncombustible construction the roof coverings must have a fire classification of Class A, B or C. In such cases the use of fire-retardant treated wood shakes and shingles on sloped roofs is allowed.