Code Library › Volume 1 › Section 9.21 — Masonry and Concrete Chimneys
PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code

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. (See Note A-9.21.5.1.(1)) (2) A clearance of not less than 150 mm shall be provided between a cleanout opening and combustible material. (3) Combustible flooring, subflooring and ceiling finishes shall have not less than a 12 mm clearance from masonry or concrete chimneys.
← Previous9.21.4.10. FlashingNext →9.21.5.2. Sealing of Spaces

Common questions about this part of the code

How high does a chimney have to extend above the roof in Ontario?What are the flue lining requirements for masonry chimneys in Ontario?What clearance does a masonry chimney need from combustible materials in Ontario?

Understand this provision in seconds

BUILDAiD Assist explains any article of the building code in plain English — with exact citations, exceptions and related requirements.

Try BUILDAiD Beta

Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.