The Ontario Building Code | Lateral Stability
9.21.4.5. Lateral Stability
(1) Except as provided in Sentence (2), chimneys shall be braced in accordance with Subsection 4.3.2. to provide stability under wind loads.
(2) Achimney need not be laterally braced provided,
(a) no horizontal outside dimension is less than 400 mm, and
(b) the chimneyextends not more than 3.6 m above a roof or the masonry wall of which it forms a part.
In Plain Language
Chimneys need lateral stability meeting the requirements set out in this article, preventing this tall, narrow structure from toppling under wind or seismic loads.
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.