Fire Resistance of Exterior Wall Assemblies for Housing and Small Buildings

This paper presents the fire resistance results of 6 full-scale exterior wall assemblies study conducted at the National Research Council of Canada jointly with the North American construction industry and other Canadian government departments. The parameters investigated include: cavity insulation types (rock, glass and cellulose fibre) in exterior wall assemblies with oriented strand board sheathing; cavity insulation types (glass fibre and cellulose fibre) in exterior wall assemblies with Type X gypsum glass mat sheathing; and assemblies with different screw spacing of standard 400 mm o.c. and non-standard 200 mm o.c. for attaching the Type X gypsum board on the fire-exposed side and glass mat sheathing board on unexposed side to wood studs using glass fibre insulation in wall cavity. The impact of the investigated parameters on the fire resistance of exterior wall assemblies is discussed. Also, Further research recommendations on design changes to enhance the fire resistance of exterior wall assemblies are proposed. Results of the parameters studied showed that the effect of insulation types on the fire resistance of exterior wall assemblies with OSB sheathing can be considered significant when gypsum board on the fire-exposed side is attached to wood studs with screws spaced at 406 mm o.c., however, the effect insulation types on fire resistance when the gypsum board on fire-exposed side and gypsum glass mat sheathing are attached to wood studs with screw spaced at 203 mm o.c. can be considered insignificant. Also, results showed the use of non-standard screw spacing at 203 mm o.c. for attaching the gypsum board on the fire-exposed side increased the fire resistance by 37% compared to screw spacing at 406 mm o.c. Therefore, the effect of screw spacing on the fire resistance of exterior wall is significant.