The Ontario Building Code | Required Underlay
9.30.2.1. Required Underlay
(1) A panel-type underlay shall be provided under resilient flooring, parquet flooring, ceramic tile, felted-synthetic-fibre floor coverings or carpeting laid over lumber subflooring.
(2) A panel-type underlay shall be provided under resilient flooring, parquet flooring, felted-synthetic-fibre floor coverings or carpeting on panel-type subflooring whose edges are unsupported.
(3) Panel-type underlay shall be provided under ceramic tile applied with adhesive.
(4) Panel-type underlay shall be provided under resilient flooring on waferboard or strandboard subflooring.
In Plain Language
An underlay is required beneath certain finish flooring materials, as set out in this article, providing a smooth, stable base.
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.