OBC 2024 Guide: Combustible Construction, Wiring Plenums, and Heavy Timber Standards
Sarah's Expert Insight
OBC Compliance Specialist
"For developers in London and Muskoka, correctly identifying FT6 vs FT4 cable ratings in plenums and ensuring heavy timber dimensions meet Article 3.1.4.7 is essential for passing fire inspections. At empcontracting.ca Inc. your construction contractor in London, Ontario, we specialize in implementing these technical requirements to ensure your project remains safe and fully compliant with the latest 2024 Ontario Building Code updates."
Understanding Wiring and Cable Requirements in Plenums
Under Section 3.1.4.3 of the Ontario Building Code, optical fibre and electrical cables installed in plenums within combustible construction buildings must adhere to strict fire safety ratings. Specifically, cables must meet the FT6 rating (CAN/ULC-S102.4), ensuring a flame distance of no more than 1.5 m and low smoke density. If using noncombustible raceways, an FT4 rating may be permissible for certain configurations.
Standards for Fire-Retardant-Treated Wood
When the OBC specifies fire-retardant-treated wood, it must be pressure impregnated according to the CAN/CSA-O80 Series. For optimal fire safety in Ontario builds, this wood must maintain a flame-spread rating of 25 or less. Using compliant materials is vital for the structural integrity and legal standing of your project.
Heavy Timber Construction Alternatives
In scenarios where combustible construction is permitted and fire-resistance ratings do not exceed 45 minutes, heavy timber is a viable and aesthetically pleasing alternative. According to Article 3.1.4.7, these wood elements must be arranged in solid masses with smooth surfaces to prevent rapid ignition.
Minimum Dimensions for Heavy Timber Floors
To qualify as heavy timber construction under the OBC, flooring must consist of glued-laminated or solid sawn planks with specific minimum thicknesses:
- 64 mm thick if splined or tongued and grooved.
- 38 mm wide and 89 mm deep when set on edge and well-spiked.
Navigating these technical specifications requires a partner who understands the nuances of the 2024 Compendium. Contact empcontracting.ca Inc. your construction contractor in London, Ontario, for expert guidance on your next build.
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.