The Ontario Building Code | Preservation Treatment of Wood
4.2.3.2. Preservation Treatment of wood
(1) wood exposed to soil or air above the lowest anticipated groundwater table shall be treated with preservative in conformance with CAN/CSA-O80 Series, "wood Preservation", and the requirements of the appropriate commodity standard as follows:
(a) CAN/CSA-O80.2, "Processing and Treatment",
(b) CAN/CSA-O80.3, "Preservative Formulations", or
(c) CSA O80.15, "Preservative Treatment of wood for building Foundation Systems, basements and Crawl Spaces by pressure Processes".
In Plain Language
Wood exposed to soil or air above the anticipated groundwater table must be treated with preservative per the referenced standard, protecting foundation-adjacent wood from decay in a persistently damp environment.
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.