The Ontario Building Code | Materials
9.26.6.1. Materials
(1) Except as required in Sentence (2), when underlay is used beneath shingles, it shall be,
(a) asphalt-saturated sheathing paper weighing not less than 0.195 kg/m², or
(b) No. 15 plain or perforated asphalt-saturated felt.
(2) Underlay used beneath wood shingles shall be breather type.
In Plain Language
Materials for this roofing component must conform to the standards referenced in this article.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.