Ontario Building Code Fireplace Standards: A Guide for London and Oakville Homeowners
Sarah's Expert Insight
OBC Compliance Specialist
"In high-end builds across London and the Muskoka cottage country, I often see homeowners overlook the specific 400mm hearth extension requirement, which is a critical safety failure. At empcontracting.ca Inc., we ensure that masonry and liner thickness are prioritized during the framing stage to prevent costly retrofits and ensure your fireplace is a safe, warm centerpiece for your home."
Compliance for Fireplace Installations in Ontario
Ensuring your home meets the 2024 Ontario Building Code (OBC) is essential for safety, longevity, and insurance compliance. When working with empcontracting.ca Inc. your construction contractor in London, Ontario, you can rest assured that every fireplace detail, from the firebox to the hearth, meets provincial standards.
Section 9.22.2: Brick and Steel Fireplace Liners
The OBC requires every fireplace to have a firebrick liner unless a specialized steel liner is installed. Firebrick liners must be at least 50 mm thick for the sides and back, and 25 mm thick for the floor. These must be laid with high-temperature cement mortar conforming to CAN/CGSB-10.3. If opting for steel, the assembly must conform to CAN/ULC-S639M.
Section 9.22.3: Fireplace Wall Thickness Requirements
To prevent heat transfer to adjacent structures, the back and sides of a fireplace must have a total thickness of at least 190 mm. This includes the thickness of the liner. Exceptions are made for steel liners with air-circulating chambers, where solid masonry can be reduced to 90 mm.
Section 9.22.4 & 9.22.5: Fire Chamber and Hearth Dimensions
Safety dimensions are strictly regulated under the OBC:
- Fire Chamber: The depth from the back to the opening must be at least 300 mm.
- Hearth Extension: To protect your flooring, a noncombustible hearth must extend 400 mm in front of the fireplace and 200 mm past each side of the opening.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.