The Ontario Building Code | Topping Course
9.16.4.2. Topping Course
(1) Where a topping course is provided for a concrete floor slab, it shall consist of 1 part cement to 2.5 parts clean, well graded sand by volume, with a water/cement ratio approximately equal to that of the base slab.
(2) When concrete topping is provided it shall not be less than 20 mm thick.
In Plain Language
A topping course, an additional layer of concrete or other material placed over the structural slab, must meet the requirements set out in this article where used.
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.