(1) Where dampproofing is installed below the floor, it shall consist of,
(a) polyethylene not less than 0.15 mm thick with joints lapped not less than 100 mm,
(b) Type S roll roofing with joints lapped not less than 100 mm, or
(c) rigid extruded/expanded polystyrene with sealed or ship-lapped joints that has,
(i) sufficient compressive strength to support the floor assembly, and
(ii) a water vapour permeance complying with Clause 9.13.2.2. (2) (b).
(2) Where dampproofing is installed between a floor-on-ground and a finished floor, it shall consist of,
(a) rigid extruded/expanded polystyrene with sealed or ship-lapped joints that has,
(i) sufficient compressive strength to support the floor assembly, and
(ii) a water vapour permeance complying with Clause 9.13.2.2. (2) (b), or
(b) polyethylene not less than 0.05 mm with joints lapped not less than 100 mm.