The Ontario Building Code | Materials and Thickness
9.30.2.2. Materials and Thickness
(1) panel-type underlay shall be not less than 6 mm thick and shall conform to,
(a) ANSI A208.1, "Particleboard",
(b) CAN/cgsb-11.3-M, "Hardboard",
(c) CSA O115-M, "Hardwood and Decorative Plywood",
(d) CSA O121, "Douglas Fir Plywood",
(e) CSA O151, "Canadian Softwood Plywood",
(f) CSA O153-M, "Poplar Plywood", or
(g) CSA O437.0, "OSB and Waferboard".
In Plain Language
Underlay materials and thickness must meet the requirements set out 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.