Built-Up Roofs Quantity of Materials

(1)  The quantities of bituminous materials used on built-up roofs shall conform to Table

Article Ontario Regulation 332/12 Building Code,   Information published by oncodes.ca for educational purposes only.

Built-up Roofs

Built-up roof coverings should be installed by specialized roofing installers. A built-up roof may have three or more layers of roofing felt. Each layer, including the final layer, is sealed with tar or asphalt. The surface is then covered with gravel (embedded in the asphalt or tar) or with a cap sheet. This covering provides ballast against wind uplift and protection from the sun.

Coal tar products and asphalt products are not compatible and must not be used together.

The eave line of projecting roofs is trimmed with metal edging or flashing to direct water away from the fascia board. A gravel stop or cant strip is used in conjunction with the flashing at the eaves when the roof is covered with gravel (Figure 105). Where built-up roofing abuts a wall (except a masonry-clad wall), the roofing is mopped to the cant strip and turned up the wall at least 150 mm (6 in.). The wall sheathing paper and siding is then lapped over the roof membrane).

Where a built-up roof intersects a masonry-clad wall, the roof membrane is turned up the face of the masonry and a flashing is installed over the membrane. A counter-flashing should be embedded into the mortar joints at least 25 mm (1 in.), extend down the wall about 150 mm (6 in.) and lap over the membrane flashing at least 100 mm (4 in.).

Single-ply membranes can also be used for low-slope roofs including the small roofs typical of wood-frame construction.

Figure 105

Built-up roof

Source : Canada Mortgage and Housing Corporation (CMHC)