9.13.4.2.

(1) Except as provided in Sentence (2), all wall, roof and floor assemblies in contact with the ground shall be constructed to resist the leakage of soil gas from the ground into the building.

(2) Construction to resist leakage of soil gas into the building is not required for,

(a) garages and unenclosed portions of buildings,

(b) buildings constructed in areas where it can be demonstrated that soil gas does not constitute a hazard, or

(c) buildings that contain a single dwelling unit and are constructed to provide for subfloor depressurization in accordance with Supplementary Standard SB-9.

(3) Where soil gas control is required, a soil gas barrier shall be installed at walls and roofs in contact with the ground according to Supplementary Standard SB-9.

(4) Where soil gas control is required, it shall consist of one of the following at floors in contact with the ground:

(a) a soil gas barrier installed according to Supplementary Standard SB-9 , or

(b) where the building contains a single dwelling unit only, a subfloor depressurization system installed according to Supplementary Standard SB-9.