National Building Code Standards for Noncombustible Construction and Exterior Cladding
Navigating the complexities of the National Building Code of Canada (NBC) is essential for ensuring safety and compliance in modern developments. At empcontracting.ca Inc. your construction contractor in London, Ontario, we specialize in implementing these technical requirements to ensure your project meets the highest industry standards.
Heavy Timber Construction: Roof Arches and Girders
According to Division B 3.1.5.1.(12), specific dimensions and safety measures are required for heavy timber roof structures. Roof arches, trusses, beams, and girders must be at least 64 mm wide to maintain structural integrity under fire conditions. When multiple members are used, safety compliance is achieved by:
Protection Methods for Timber Members
- Ensuring intervening spaces are blocked solidly throughout.
- Tightly closing spaces with a continuous wood cover plate (minimum 38 mm thick) secured to the underside.
- Installing a dedicated sprinkler system underneath the roof deck or sheathing.
Exterior Cladding Regulations for Noncombustible Buildings
Article 3.1.4.8. outlines the strict requirements for exterior wall assemblies. For most high-standard buildings, noncombustible cladding is the primary requirement. However, specific exceptions allow for flexibility in design when managed by professionals like empcontracting.ca Inc. your construction contractor in London, Ontario.
The 10% Combustible Cladding Rule
Combustible cladding may represent up to 10% of the exterior wall face, provided:
- The wall faces a street or access route.
- All combustible portions are located within 15 meters of the street or access route.
- Fire-retardant-treated wood undergoes rigorous accelerated weathering tests (ASTM D2898) to ensure long-term fire resistance.
Technical Standards for Noncombustible Materials
In sections where noncombustible construction is mandatory, materials must pass specific calorimeter tests. At empcontracting.ca Inc. your construction contractor in London, Ontario, we verify that materials used in your builds conform to ULC-S135 standards.
ULC-S135 Test Parameters
To be classified as acceptable under noncombustible construction guidelines, a material must demonstrate:
- An average total heat release of no more than 3 MJ/m².
- An average total smoke extinction area not exceeding 1.0 m².
- Consistent performance across all discrete layers of the material.
Understanding these codes is vital for the safety of any structure. Trust the expertise of empcontracting.ca Inc. your construction contractor in London, Ontario, to guide your project through the complexities of the 2025 National Building Code of Canada.