2024 Ontario Building Code Guide: Encapsulated Mass Timber and Fire Safety for London Projects
Sarah's Expert Insight
OBC Compliance Specialist
"As London and Oakville move toward sustainable mid-rise developments, adhering to the 2024 OBC encapsulation ratings is critical for fire safety and insurance compliance. At empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every CLT panel and adhesive bond meets the rigorous ANSI/APA PRG 320 standard to guarantee structural integrity and code approval during municipal inspections in Southwestern Ontario and the Muskoka region."
The 2024 Ontario Building Code (OBC) introduces stringent standards for encapsulated mass timber construction, focusing on structural integrity and fire protection. Understanding these requirements is essential for developers and builders working with cross-laminated timber (CLT) and other mass timber elements.
Adhesives and Fire Performance in Structural Timber
According to 3.1.6.4.(3), adhesives used in structural mass timber, specifically CLT, must conform to the elevated temperature performance requirements of ANSI/APA PRG 320. This ensures that the structural bond remains intact even under significant thermal stress.
Managing Concealed Spaces within Timber Elements
Concealed spaces in mass timber buildings present unique fire-safety challenges. Under Section 3.1.6.4.(4), these spaces are permitted only if they meet specific criteria:
- Installation of sprinklers and fire blocks per Subsection 3.1.11.
- Full encapsulation with rock or slag fibre insulation (minimum density of 32 kg/m³).
- Lining horizontal or vertical spaces with at least 12.7 mm Type X gypsum board to provide a minimum 25-minute encapsulation rating.
Minimum Dimensions for Structural Mass Timber Elements
Table 3.1.6.3 outlines the minimum dimensions required for various wood elements to maintain fire-resistance ratings:
- Walls (Fire Separations): Minimum 96 mm thickness.
- Beams and Columns (4-sided exposure): Minimum 224 x 224 mm.
- Floors and Roofs: Minimum 96 mm thickness.
Encapsulation Ratings and Protection
Section 3.1.6.4.(1) mandates that exposed surfaces of mass timber must be protected by materials providing an encapsulation rating of at least 50 minutes for most major occupancies. Permitted materials include gypsum board, gypsum concrete, and other approved noncombustible materials as defined in the code.
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.