The Ontario Building Code | Size of Chimney Flues
9.21.2.4. Size of Chimney Flues
(1) Except for chimneys serving fireplaces, the size of a chimney flue shall conform to the requirements of the solid fuel-burning applianceinstallation standard referenced in Sentence 6.2.1.4.(1) and Article 9.33.1.2.
(2) Where a chimney flue serves only one solid fuel-burning appliance, the flue area shall be at least equal to that of the flue pipeconnected to it.
In Plain Language
Chimney flues must be sized as set out in this article, matching flue capacity to the appliance or appliances being vented.
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.