The Ontario Building Code | Rating of Supporting Construction
3.1.7.5. Rating of supporting Construction
(1) Except as permitted by Sentence (2) and by Articles 3.2.2.20. to 3.2.2.83. for mixed types of construction, all loadbearingwalls, columns and arches in the storey immediately below a floor or roof assembly required to have a fire-resistance rating shall have a fire-resistance ratingnot less than that required for the supported floor or roof assembly.
(2) loadbearingwalls, columns and arches supporting a service roomor service space need not conform to Sentence (1).
(3) Except for noncombustible constructionrequired by Subclauses 3.2.2.43A.(2)(c)(i) and 3.2.2.50A.(2)(c)(i), if an assembly is required to be of noncombustible constructionand have a fire‑resistance rating, it shall be supported by noncombustible construction.
3.1.8. Fire Separations and Closures
In Plain Language
Loadbearing walls, columns, and arches directly below a rated floor or roof assembly must generally match or exceed that assembly's fire-resistance rating, though supports for service rooms/spaces are exempted, and further exceptions apply for certain noncombustible-construction cases.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.