The Ontario Building Code | Firewalls
4.1.5.17. Firewalls
(1) Firewalls shall be designed to resist the maximum effect due to,
(a) the appropriate lateral design loads prescribed elsewhere in this Section, or
(b) a factored lateral load of 0.5 kPa under fire conditions, as described in Sentence (2).
(2) Under fire conditions, where the fire-resistance rating of the structure is less than that of the firewall,
(a) lateral support shall be assumed to be provided by the structure on one side only, or
(b) another structural support system capable of resisting the loads imposed by a fire on either side of the firewall shall be provided.
4.1.6. Loads Due to Snow and Rain
In Plain Language
Firewalls must be designed to resist whichever is greater: the lateral design loads that would otherwise apply, or a specified factored lateral load representing the pressure a firewall could experience during an actual fire.
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.