9.26.3.1.Slope

(1) Except as provided in Sentences (2) and (3), the slopes on which roof coverings may be applied shall conform to Table 9.26.3.1. (2) Asphalt and gravel or coal tar and gravel roofs may be constructed with lower slopes than required in Sentence (1) when effective drainage is provided by roof drains located at the lowest points on the roofs. (3) Profiled metal roof cladding systems specifically designed for low-slope applications are permitted to be installed with lower slopes than required in Sentence (1), provided they are installed in conformance with the manufacturer’s written recommendations. (4) Except where back-slope will not adversely affect adjacent supported or supporting constructions due to water ingress, roofs and constructions that effectively serve as roofs shall be constructed with sufficient slope away from (a) exterior walls, and (b) guards that are connected to the roof, or to a construction that effectively serves as a roof, by more than pickets or posts. (See Notes A-9.26.1.1.(1), A-9.26.4.1. and A-9.27.3.8.(4)) (5) The slope required in Sentence (4) shall be sufficient to maintain a positive slope (a) after expected shrinkage of the building frame, where these surfaces are supported by exterior walls and on exterior columns, and (See Note A-9.27.3.8.(4)) (b) once design loading is taken into consideration, where these surfaces are cantilevered from exterior walls. Table 9.26.3.1. Roofing Types and Slope Limits Forming Part of Sentence 9.26.3.1.(1) Type of Roofing Minimum Slope Maximum Slope Asphalt Shingles Low slope application 1 in 6 no limit Normal application 1 in 3 no limit Built-up Roofing Asphalt base (without gravel) 1 in 25 1 in 2 Asphalt base (gravelled) 1 in 50(1) 1 in 4 Coal-tar base (gravelled) 1 in 50(1) 1 in 25 Cold process 1 in 25 1 in 1.33 Cedar Shakes 1 in 3 no limit Clay Tile 1 in 2 no limit Glass Fibre Reinforced Polyester Roofing Panels 1 in 4 no limit Modified Bituminous Membranes 1 in 50 1 in 4 Profiled Metal Roofing 1 in 4(2) no limit Roll Roofing 480 mm wide selvage asphalt roofing 1 in 6 no limit Cold application felt 1 in 50 1 in 1.33 Smooth and mineral surfaced 1 in 4 no limit Sheet Metal Shingles 1 in 4(2) no limit Slate Shingles 1 in 2 no limit Wood Shingles 1 in 4 no limit Notes to Table 9.26.3.1.: (1) See Sentence 9.26.3.1.(2). (2) See Sentence 9.26.3.1.(3).