The Ontario Building Code | Crawl Spaces
3.2.2.9. Crawl Spaces
(1) For the purposes of Articles 3.2.1.4. and 3.2.1.5., a crawl space shall be considered as a basement if it is,
(a) more than 1 800 mm high between the lowest part of the floor assembly and the ground or other surface below,
(b) used for any occupancy,
(c) used for the passage of flue pipes, or
(d) used as a plenumin combustible construction.
(2) A floor assembly immediately above a crawl space is not required to be constructed as a fire separation and is not required to have a fire-resistance rating provided the crawl space is not required to be considered as a basementby Sentence (1).
In Plain Language
A crawl space counts as a basement for fire-separation purposes if it's taller than 1,800 mm, used for any occupancy, used to route flue pipes, or used as a plenum in combustible construction; otherwise the floor above it doesn't need to be a rated fire separation.
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.