Notice: This site currently shows the 2012/2017 edition of the Ontario Building Code. The current legally effective code is the 2024 edition (O.Reg. 163/24), in effect since January 1, 2025. Confirm current requirements at ontario.ca.
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The Ontario Building Code | Concrete Units Exposed to the Weather

9.20.2.6. Concrete Units Exposed to the Weather

(1) Concrete blocks exposed to the weather shall have weight and water absorption characteristics conforming to Classes A, B, C or D, described in CAN/CSA-A165.1, "Concrete Block masonry Units".

In Plain Language

Concrete masonry units exposed to the weather must meet the requirements set out in this article, since exterior exposure demands greater durability and freeze-thaw resistance.

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.