Intersection of Built-Up Roofs and Masonry

(1)  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.


(2)  Counter flashing installed over the intersection referred to in Sentence (1) shall be embedded not less than 25 mm in the masonry, and shall be of sufficient length to extend down not less than 150 mm, lapping the membrane on the masonry not less than 100 mm.

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

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

Build-up Roof

Source : Canada Mortgage and Housing Corporation (CMHC)