The Ontario Building Code | Required Waterproofing
9.13.3.1. Required waterproofing
(1) Where hydrostatic pressure occurs, waterproofing is required for exterior surfaces of,
(a) floors-on-ground, and
(b) below ground walls, where the exterior finished ground level is at a higher elevation than the ground level inside the foundation walls.
(2) Roofs of underground structures shall be waterproofed to prevent the entry of water into the structure.
In Plain Language
Waterproofing, a more robust moisture barrier than dampproofing, is required under the conditions set out in this article, addressing sites where actual water pressure against the foundation is expected.
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.