The Ontario Building Code | Restraint of Joist Bottoms
9.23.13.9. Restraint of Joist Bottoms
(1) Roof joists supporting a finished ceiling, other than plywood, OSB or waferboard, shall be restrained from twisting along the bottom edges by means of furring, blocking, cross bridging or strapping conforming to Article 9.23.9.3.
In Plain Language
The bottom of a joist needs restraint against rotation, as set out in this article, similar in purpose to the floor joist restraint requirement but applied to roof framing.
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.