The Ontario Building Code | Compressive Strength
9.3.1.6. Compressive Strength
(1) Except as provided elsewhere in this Part, the compressive strength of unreinforced concrete after 28 days shall be not less than,
(a) 32 MPa for garage floors, carport floors and all exterior flatwork,
(b) 20 MPa for interior floors other than those for garages and carports, and
(c) 15 MPa for all other applications.
(2) Concrete used for garage and carport floors and exterior steps shall have air entrainment of 5 to 8%.
In Plain Language
Concrete must achieve the minimum compressive strength set out in this article for its intended use, ensuring it can safely carry the loads it will be subjected to.
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.