The Ontario Building Code | Required Moisture Protection
5.8.2.1. Required moisture Protection
(1) Except as provided in Sentence (2), where a building element separates interior space from the ground, materials, components or assemblies shall be installed to prevent moisture transfer into the space.
(2) Materials, components or assemblies need not be installed to prevent moisture transfer from the ground where it can be shown that such transfer will not adversely affect any of,
(a) the health or safety of building users,
(b) the intended use of the building, or
(c) the operation of building services.
In Plain Language
Except in specific cases, where a building element separates interior space from the ground, materials, components, or assemblies must provide the required moisture protection against ground-sourced water.
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.