Code Library › Volume 1 › Section 9.13 — Dampproofing, Waterproofing and
PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code

9.13.3.1.Required Waterproofing

(1) Where hydrostatic pressure occurs, waterproofing is required for assemblies separating interior space from the ground to prevent the ingress of water into building assemblies and interior spaces. (2) Waterproofing is required for roofs of underground structures to prevent the ingress of water into building assemblies and interior spaces.
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Common questions about this part of the code

When is waterproofing required instead of dampproofing for a foundation in Ontario?What are the radon and soil gas control requirements for new houses in Ontario?Does foundation dampproofing go on the inside or outside of the wall in Ontario?

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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.