NBC Fire Block Standards for Horizontal Concealed Spaces and Crawl Spaces
Understanding the National Building Code of Canada (NBCC) is essential for ensuring the safety and compliance of any residential or commercial build. When managing fire safety in combustible construction, empcontracting.ca Inc. your construction contractor in London, Ontario, ensures every horizontal concealed space meets the rigorous standards set out in Division B Section 3.1.11.
3.1.11.5. Fire Blocks in Horizontal Concealed Spaces
In combustible floor or roof assemblies that are not sprinklered, fire blocks are required to separate horizontal concealed spaces into specific compartments. This prevents the rapid spread of fire through hidden areas of a building.
Compartment Size and Flame-Spread Ratings
The maximum size of these compartments depends on the flame-spread rating of the exposed materials within the space:
- Flame-Spread Rating ≤ 25: Spaces must be separated into compartments no larger than 600 m² with no dimension exceeding 60 m.
- Flame-Spread Rating > 25: Spaces must be separated into compartments no larger than 300 m² with no dimension exceeding 20 m.
Exterior Elements and Timber Construction
Fire blocks are also required in exterior cornices, mansard-style roofs, balconies, and canopies where materials have a flame-spread rating higher than 25. For modern builds involving encapsulated mass timber construction (under Articles 3.2.2.48. or 3.2.2.57.), similar compartmentation rules apply to ensure structural integrity during a fire event.
Exemptions for Insulated Spaces
Compliance can also be achieved through insulation. Fire blocks are not required if the horizontal concealed space is entirely filled with non-combustible insulation, provided any air gap at the top does not exceed 50 mm.
3.1.11.6. Fire Blocks in Crawl Spaces
Crawl spaces that are not considered basements and are not protected by sprinklers must be compartmentalized. According to NBC standards, these areas must be separated by fire blocks into compartments that are:
- No more than 600 m² in area.
- No more than 30 m in any single dimension.
3.1.11.7. Fire Block Material Standards
The materials used for fire blocking must be durable and effective. Except for specific allowed variations, fire blocks must be capable of remaining in place and preventing the passage of flames for at least 15 minutes when tested against the CAN/ULC-S101 standard, "Standard Method of Fire Endurance Tests of Building Construction and Materials."
Expert Compliance in London, Ontario
Navigating the complexities of the National Building Code requires a professional eye. For expert installation and code-compliant framing, trust empcontracting.ca Inc. your construction contractor in London, Ontario, to handle your project with precision and safety at the forefront.