The Ontario Building Code | Concrete Topping
9.23.4.4. Concrete Topping
(1) Except as permitted in Sentence (2), where a floor is required to support a concrete topping, the joist spans shown in Table A-1 or the spacing of the members shall be reduced to allow for the loads due to the topping.
(2) Where a floor is required to support a concrete topping, joist spans are permitted to be selected from Table A-2 provided the concrete,
(a) is 38 to 51 mm thick,
(b) is normal weight,
(c) is placed directly on the subflooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring, and
(d) has not less than 20 MPa compressive strength after 28 days.
(3) Where a floor is required to support a concrete topping not more than 51 mm thick, the beam spans shown in Tables A-8 to A-11 shall be multiplied by 0.8 or the supported length of the floor joists shall be reduced to allow for the loads due to the topping.
In Plain Language
Where a concrete topping is added over a wood floor structure, this article sets out how that additional weight must be accounted for in design.
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.