The Ontario Building Code | Joints Offset
9.30.2.4. Joints Offset
(1) Where panel-type underlay is required to be installed over plywood, or OSB or waferboard, the joints in the underlay shall be offset at least 200 mm from the joints in the underlying subfloor.
In Plain Language
Where panel-type underlay (like hardboard or particleboard) goes over a plywood, OSB, or waferboard subfloor, this clause requires the underlay joints to be offset at least 200 mm from the subfloor joints beneath, so the two layers don't share weak points.
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.