The Ontario Building Code | Spaces Between Liners and Surrounding Masonry
9.21.3.8. Spaces Between liners and Surrounding masonry
(1) A space not less than 10 mm wide shall be left between a chimney liner and the surrounding masonry.
(2) The space required in Sentence (1) shall not be filled with mortar.
In Plain Language
Spaces between a chimney liner and the surrounding masonry must meet the requirements set out in this article, addressing how this gap is managed for both safety and structural performance.
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.