PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code
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9.29.9.2.Minimum Thickness
(1) Except as provided in Sentences (2) and (3), the minimum thickness of O-2 grade OSB used as an interior finish
shall conform to that shown for plywood in Table 9.29.6.1.
(2) Thicknesses listed in Table 9.29.6.1. shall permit a manufacturing tolerance of –0.4 mm.
(3) No minimum thickness is required where O-2 grade OSB is applied over continuous backing.
(4) OSB conforming to O-1 grade, waferboard conforming to R-1 grade and particleboard shall be
(a) not less than 6.35 mm thick on supports not more than 400 mm o.c.,
(b) not less than 9.5 mm thick on supports not more than 600 mm o.c., and
(c) not less than 6.35 mm thick on supports not more than 600 mm o.c. in walls where blocking is provided at mid-wall
height.
(5) OSB conforming to CSA O325, “Construction sheathing,” shall meet the minimum panel mark of
(a) W16, on supports not more than 400 mm o.c.,
(b) W24, on supports not more than 600 mm o.c., and
(c) W16, on supports not more than 600 mm o.c. where blocking is provided at mid-wall height.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.