The Alberta Building Code: Roofing
When hiring a roofing contractor, it is important that you ensure they follow the requirements of the Alberta Building Code. The code has very specific rules. This is a summary of some of the major requirements.
Roofs shall be protected with roofing, including flashing, installed to shed rain effectively and prevent water due to ice damming from entering the roof.
- Controlling the flow of moisture by air leakage and vapour diffusion into attic or roof spaces is necessary to limit moisture-induced deterioration. Given that imperfections normally exist in the vapour barriers and air barrier systems, recent research indicates that venting of attic or roof spaces is generally still required.
- Except where it can be shown to be unnecessary, where insulation is installed between a ceiling and the underside of the roof sheathing, a space shall be provided between the insulation and the sheathing, and vents shall be installed to permit the transfer of moisture from the space to the exterior.
- The unobstructed vent area shall be not less than 1/300 of the insulated ceiling area.
- Where the roof slope is less than 1 in 6 or in roofs that are constructed with roof joists, the unobstructed vent area shall be not less than 1/150 of the insulated ceiling area.
- Required vents may be roof type, eave type, gable-end type or any combination thereof, and shall be distributed
- uniformly on opposite sides of the building,
- with not less than 25% of the required openings located at the top of the space, and with not less than 25% of the required openings located at the bottom of the space.
- The intersection of shingle roofs and masonry walls or chimneys shall be protected with flashing.
- The intersection of shingle roofs and walls clad with other than masonry shall be protected with flashing.
- The intersection of built-up roofs with masonry walls or chimneys shall have a cant strip at the intersection, and a roofing membrane shall be mopped over the cant strip and not less than 150 mm up the wall.
- Where a pipe or duct penetrates a roof, the joint between the pipe or duct and the roof shall be flashed and be made watertight.
- Where sloping surfaces of shingled roofs intersect to form a valley, the valley shall be flashed.
- Valley flashing shall be installed over continuous sheathing.
- Closed valleys shall not be used with rigid shingles on slopes of less than 1 in 1.2.
- Open valleys shall be flashed with at least
- one layer of sheet metal not less than 600 mm wide, or 2 layers of roll roofing.
- Eave protection shall be provided on shingle, shake or tile roofs, extending from the edge of the roof a minimum of 900 mm up the roof slope to a line not less than 300 mm inside the inner face of the exterior wall.
- Eave protection is not required:
- over unheated garages, carports and porches,
- where the roof overhang exceeds 900 mm measured along the roof slope from the edge of the roof to the inner face of the exterior wall,
- on roofs of asphalt shingles with slopes of less than 1 in 3,
- on roofs with slopes of 1 in 1.5 or greater, or in regions with 3,500 or fewer degree-days.
Asphalt Shingles on Slopes of 1 in 3 or Greater
A starter strip shall be installed along the lower edge of the roof so that it extends approximately 12 mm beyond the eaves and rake of the roof and fastened along the bottom edge with nails spaced not more than 300 mm o.c.
Asphalt Shingles on Slopes of less than 1 in 3
- Except for the first 2 courses, coverage shall be not less than 3 thicknesses of shingle over the entire roof, disregarding cutouts.
- A starter strip shall be installed along the lower edge of the roof so that it extends approximately 12 mm beyond the eaves and rake of the roof and fastened along the bottom edge with nails spaced not more than 300 mm o.c.
- Starter strips shall be laid in a continuous band of cement not less than 200 mm wide.