The Ontario Building Code | Concrete Masonry Units
9.28.1.3. Concrete masonry Units
(1) stucco finish shall not be applied over concrete masonry units less than one month old unless the units have been cured by the autoclave process.
In Plain Language
Concrete masonry units used as a stucco substrate must meet the requirements set out in this article.
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.