Wood Cladding Systems

The NBCC contains the rules on the use of combustible claddings and supporting assemblies on certain types of noncombustible buildings. Specifically, the use of wall assemblies containing both combustibles cladding elements and non-load-bearing wood framing members is allowed.

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These wall assemblies can be used as in-fill or panel type walls between structural elements, or be attached directly to a load-bearing noncombustible structural system. This applies in unsprinklered buildings up to three storeys and sprinklered buildings of any height.

The wall assembly must satisfy the criteria of a test that determines its degree of flammability and the interior surfaces of the wall assembly must be protected by a thermal barrier (for example, 12.7mm gypsum wallboard) to limit the impact of an interior fire on the wall assembly.

These requirements stem from fire research that indicated that certain wall assemblies containing combustible elements do not promote fire spread beyond a limited distance.

The ULC test standard, CAN/ULC-S134, Standard Method of Fire Test of Exterior Wall Assemblies is referenced in the NBCC. Each assembly must be tested in accordance with this standard to confirm compliance with fire spread and heat flux limitations specified in the code.

Wood Fascias and Canopies

Fire - retardant treated wood (FRTW) decorative cladding is permitted on first floor canopy fascias. In this case, the wood must undergo accelerated weathering before testing to establish the flame-spread rating. An FSR of 25 or less is required.