The Ontario Building Code | Fire-Retardant Treated Wood Roof Systems
3.1.14.1. Fire-Retardant Treated wood Roof Systems
(1) If a fire-retardant treated wood roof system is used to comply with the requirements of Subsection 3.2.2., the roof deck assembly shall meet the conditions of acceptance of CAN/ulc-S126, "Test for Fire Spread Under Roof-Deck Assemblies".
(2) supports for the roof deck assembly referred to in Sentence (1) shall consist of,
(a) fire-retardant treated wood,
(b) heavy timber construction,
(c) noncombustible construction, or
(d) a combination of the items described in Clauses (a) to (c).
In Plain Language
A fire-retardant treated wood roof system used to satisfy Subsection 3.2.2's requirements must pass the CAN/ULC-S126 roof-deck fire-spread test, and its supports must be fire-retardant treated wood, heavy timber, noncombustible construction, or some combination of these.
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.