The Ontario Building Code | Removal of Topsoil and Organic Matter
9.12.1.1. Removal of Topsoil and Organic Matter
(1) The topsoil and vegetable matter in all unexcavated areas under a building shall be removed.
(2) In localities where termite infestation is known to be a problem, all stumps, roots and other wood debris shall be removed from the soilto a depth of not less than 300 mm in unexcavated areas under a building.
(3) The bottom of every excavation shall be free of all organic material.
In Plain Language
Topsoil and organic matter must be removed from a building site as set out in this article, since organic material beneath a foundation can decompose, settle, and undermine the structure above it.
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.