The Ontario Building Code | Clearance from Combustible Materials
9.21.5.1. Clearance from Combustible Materials
(1) The clearance between masonry or concrete chimneys and combustible framing material shall be not less than,
(a) 50 mm for interior chimneys, and
(b) 12 mm for exterior chimneys.
(2) A clearance of not less than 150 mm shall be provided between a cleanout opening and combustible material.
(3) Combustible flooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring, subflooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring and ceiling finishes shall have not less than a 12 mm clearance from masonry or concrete chimneys.
In Plain Language
A minimum clearance from combustible materials must be maintained around a chimney or flue, as set out in this article, preventing heat from igniting nearby wood framing or finishes.
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.