3.2.2.15.Storeys Below Ground

(1) If a building is erected entirely below the adjoining finished ground level and does not extend more than one storey below that ground level, the minimum precautions against fire spread and collapse shall be the same as are required for basements under a building of 1 storey in building height having the same occupancy and building area. (2) If any portion of a building is erected entirely below the adjoining finished ground level and extends more than 1 storey below that ground level, the following minimum precautions against fire spread and collapse shall be taken: (a) except as permitted by Sentence (3), the basements shall be sprinklered throughout, (b) a floor assembly below the ground level shall be constructed as a fire separation with a fire-resistance rating not less than (i) 3 h if the basements are used as Group E or Group F, Division 1 or 2 occupancies, or (ii) 2 h if the basements are not used as Group E or Group F, Division 1 or 2 occupancies, and (c) all loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the construction that they support. (3) If the first storey of a building is not required to be sprinklered, sprinklers are not required in the storey immediately below the first storey, provided the storey below (a) contains only residential occupancies, and (b) has at least one unobstructed access opening conforming to Sentence 3.2.5.1.(2) installed on that storey for each 15 m of wall length in at least one wall required by this Subsection to face a street.