The Ontario Building Code | Masonry or Concrete Chimneys
6.3.1.2. masonry or Concrete Chimneys
(1) Rectangular masonry or concrete chimneysnot more than 12 m in height shall conform to Part 9 if they serve,
(a) appliances with a combined total rated heat output of 120 kW or less, or
(b) fireplaces.
(2) masonry or concrete chimneys other than those described in Sentence (1) shall be designed and installed in conformance with the appropriate requirements in nfpa 211, "Chimneys, fireplaces, Vents and Solid Fuel-Burning Appliances".
In Plain Language
Rectangular masonry or concrete chimneys not more than 12 m in height serving specific lower-capacity appliances must conform to the simplified chimney construction requirements found in Part 9.
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.