Alternate Installation Methods
(1) Methods described in CAN3-A123.51-M, “Asphalt Shingle Application on Roof Slopes 1:3 and Steeper”, or CAN3-A123.52-M, “Asphalt Shingle Application on Roof Slopes 1:6 to Less than 1:3”, are permitted to be used for asphalt shingle applications not described in this Section.
Article 184.108.40.206 Ontario Regulation 332/12 Building Code, Information published by oncodes.ca for educational purposes only.
On pitched roofs with slopes where the rise and run are equal to or greater than 1:6, asphalt-saturated sheathing paper is applied over the roof sheathing to provide a secondary plane of protection to water that may penetrate beyond the primary plane of protection—the shingles, tiles or metal roofing.
Pitched roofs with slopes less than 1:6 require a waterproof membrane, usually consisting of one or more layers of bituminous membrane with joints shingle-lapped and welded, self-adhering “peel-and-stick”membrane, reinforced liquid applied membranes, or an EPDM (ethylene propylene diene monomer) rubber membrane. The lower pitch of these roofs does not shed or drain water as readily as a steeper pitch, and therefore requires a more robust and completely waterproof membrane.
Source : Canada Mortgage and Housing Corporation (CMHC)
Note : Prefabricated roof trusses are most often used for framing residential roofs. Rafters framed on site are sometimes used. Of the pitched roofs, the gable roof is the simplest to construct. Other pitched configurations, such as a hip or L-shape roof, can also be framed with trusses (Figure 77).