The Ontario Building Code | Storeys below Ground
18.104.22.168. Storeys below Ground
(1) If a building is erected entirely below the adjoining finished ground level and does not extend more than 1 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 heighthaving 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,
(b) a floor assembly below the ground level shall be constructed as a fire separationwith a fire-resistance rating not less than,
(i) 3 h if the basements are intended for use as Group E or Group F, Division 1 or 2 occupancies, or
(ii) 2 h if the basements are not intended for use as Group E or Group F, Division 1 or 2 occupancies, and
(c) all loadbearingwalls, 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 storeyimmediately 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 22.214.171.124.(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.