The Ontario Building Code | Slope
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.
Table 9.26.3.1.
Roofing Types and Slope Limits
Forming Part of Sentence 9.26.3.1.(1)
| Item | Column 1 Type of Roofing | Column 2 Minimum Slope | Column 3 Maximum Slope |
| 1. | Asbestos-cement Corrugated Sheets | 1 in 4 | no limit |
| 2. | asphalt Shingles |
|
|
|
| Low slope application | 1 in 6 | no limit |
|
| Normal application | 1 in 3 | no limit |
| 3. | 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 |
| 4. | Cedar Shakes | 1 in 3 | no limit |
| 5. | Clay tile | 1 in 2 | no limit |
| 6. | 1 in 4 | no limit | |
| 7. | Modified Bituminous Membranes | 1 in 50 | 1 in 4 |
| 8. | Profiled Metal Roofing | 1 in 4(2) | no limit |
| 9. | 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 |
| 10. | Sheet Metal Shingles | 1 in 4(2) | no limit |
| 11. | Slate Shingles | 1 in 2 | no limit |
| 12 | 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).
(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 elements due to water ingress, roofs and elements 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 an element that effectively serves as a roof, by more than pickets or posts.
(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
(b) once design loading is taken into consideration, where these surfaces are cantilevered from exterior walls.
9.26.4. Flashing at Intersections