The Ontario Building Code | Number of Layers
9.26.11.6. Number of Layers
(1) Built-up roofing shall consist of at least three mopped-down layers of roofing felt flood coated with bitumen.
In Plain Language
Built-up roofing must have the number of layers set out in this article, since this system's waterproofing performance depends on multiple overlapping plies.
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.