The Ontario Building Code | Surface Defects
9.30.2.5. surface Defects
(1) Underlay beneath resilient or ceramic floors applied with an adhesive shall have all holes or open defects on the surface patched so that the defects will not be transmitted to the finished surface.
9.30.3. wood Strip flooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring
In Plain Language
Underlay must be free of surface defects, as set out in this article, since irregularities can telegraph through and show in the finished floor covering.
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.