BCAB #1761 - Wall Enclosing Attic or Roof Space, Sentence 22.214.171.124.(1)
February 12, 2015
Re: Wall Enclosing Attic or Roof Space, Sentence 126.96.36.199.(1)
The project is primarily a residential building four storeys in building height, permitted to be of combustible construction. Due to the proximity to the property line the exterior wall in question is required to be of noncombustible construction having a 1 hour fire-resistance rating with no unprotected openings. The roof is a low slope (1 in 50) assembly of gypsum board on wood roof joists, cross purlins for ventilation and drainage slope, wood sheathing and waterproof roof membrane.
The edge of the roof assembly rests on top of the exterior concrete wall with three rim joists. The most outward rim joist is flush with the outer plane of the concrete wall. The outer rim joist face is finished with stucco. The combustible assembly at the wall face is approximately 430 mm in height, inclusive of a 100 mm high roof curb.
Reason for Appeal
Sentence 188.8.131.52.(1) requires an exterior wall enclosing an attic or roof space that is located above an exposing building face to be constructed to the same requirements as the exposing building face. There is a dispute as to whether or not the roof assembly creates a roof space, and whether or not the rim joist(s) form a wall enclosing a roof space, requiring similar construction to the exposing building face below.
The Appellant contends that the roof rim joist(s) are not an “exterior wall enclosing an attic or roof space” as intended by the code. Further, the appellant considers the cavity within the flat roof is not an attic or roof space, as it is not enclosed by vertical members, and that the requirements of Sentence 184.108.40.206.(1) are intended to apply to gable ends of pitched roofs or dwarf walls constructed of short studs.
Building Official's Position
The Building Official considers that the roof framing creates a roof space as defined by the code and that the rim joists located above the exposing building face forms a wall enclosing the roof space, and requires the same construction as the wall below.
Appeal Board Decision #1761
The Board considers the proposed roof framing to be a roof space as defined by the Code and the rim joists to be a vertical extension of the exterior wall below. It is therefore the determination of the Board that the vertical extension of the wall created by the roof framing is to be constructed in conformance with the requirements for the exposing building face as outlined in Sentence 220.127.116.11.(1).
Lyle Kuhnert, Chair