(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) houses that are constructed to provide for subfloor depressurization in accordance with MMAH Supplementary Standard SB-9, “Requirements for Soil Gas Control”.
(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 MMAH Supplementary Standard SB-9, “Requirements for Soil Gas Control”.
(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 MMAH Supplementary Standard SB-9, “Requirements for Soil Gas Control”, or
(b) for houses, a subfloor depressurization system installed according to MMAH Supplementary Standard SB-9, “Requirements for Soil Gas Control”.