Aug 16, 2018
Re: Nailing Elements and Cladding
The project is a 6 storey combustible apartment building. The proposed exterior wall detail includes 19mm thick by 75mm wide plywood strapping used to support noncombustible fibre-cement siding. The strapping comprises approximately 20% of the wall surface behind the fibre-cement siding.
Applicable Code Requirement
Clause 22.214.171.124.(3)(a) of Division B of the 2012 British Columbia Building Code
126.96.36.199.(3) Except as provided in Sentence (4), a building referred to in Subclause (1)(d)(v) or (d)(vi) shall have an exterior wall assembly
a) protected by noncombustible cladding,
b) protected by cladding of fire-retardant-treated wood that has been conditioned in conformance with ASTM D 2898, “Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing,” before being tested in accordance with CAN/ULC-S102, “Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies,” or
c) the interior surfaces of which are protected by a thermal barrier conforming to Sentence 188.8.131.52.(3) and that satisfies the criteria of Sentences 184.108.40.206.(3) and (4) when subjected to testing in conformance with CAN/ULC-S134, “Fire Test of Exterior Wall Assemblies.”
Decision being Appealed (Local Authority’s Position)
The local authority has determined that the strapping is not a minor combustible component as described in Subsection 3.1.5. The local authority considers the conditions of Subsection 3.1.5. to be applicable to Clause 220.127.116.11.(3)(a). Further the local authority considers cladding (fibre-cement siding) and a cladding system (fibre-cement siding including strapping and other components) to be synonymous when applying these Code requirements and therefore requires the strapping to comply with Sentence 18.104.22.168.(3).
The appellant maintains that application of the conditions of Clause 22.214.171.124.(3)(a) apply only to the cladding (fibre-cement siding), and not to the cladding system which includes the combustible strapping and other components. Thus the combustible strapping should be permitted inboard of the noncombustible siding.
Appeal Board Decision # 1814
It is the determination of the Board that the use of combustible strapping for the attachment of noncombustible cladding is not prohibited by Clause 126.96.36.199.(3)(a).
Reason for Decision
The Board considers that cladding is a component of a cladding system and the requirements of Clause 188.8.131.52.(3)(a) are limited to the cladding (the fibre-cement siding) and not to the whole cladding system. Subsection 3.1.5. is not referenced by Clause 184.108.40.206.(3)(a).
Chair, Building Code Appeal Board