The Ontario Building Code | Subfloor Thickness or Rating
9.23.14.5. Subfloor Thickness or Rating
(1) Except as provided in Sentences (2) and (3), subfloors shall conform to Table 9.23.14.5.A. or 9.23.14.5.B.
Table 9.23.14.5.A.
Thickness of Subflooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring
Forming Part of Sentences 9.23.14.5.(1) and 9.23.15.7.(1)
| Item | Column 1 Maximum Spacing of supports, mm | Column 2 Minimum Thickness, mm Plywood and OSB, O-2 Grade | Column 3 Minimum Thickness, mm OSB, O-1 Grade, and waferboard, R-1 Grade | Column 4 Minimum Thickness, mm Particleboard | Column 5 Minimum Thickness, mm Lumber |
| 1. | 406 | 15.5 | 15.9 | 15.9 | 17.0 |
| 2. | 508 | 15.5 | 15.9 | 19.0 | 19.0 |
| 3. | 610 | 18.5 | 19.0 | 25.4 | 19.0 |
Table 9.23.14.5.B.
Rating for Subfloor when Applying CSA O325
Forming Part of Sentences 9.23.14.5.(1) and 9.23.15.7.(1)
| Item | Column 1 Maximum Spacing of supports, mm | Column 2 panel Mark Subfloor | Column 3 panel Mark |
| 1. | 406 | 1F16 | 2F16 |
| 2. | 508 | 1F20 | 2F20 |
| 3. | 610 | 1F24 | 2F24 |
(2) Where the finished flooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring consists of not less than 19 mm matched wood strip flooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring laid at right angles to joists, spaced not more than 610 mm o.c., subflooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring shall be permitted to consist of not less than,
(a) 12.5 mm thick plywood,
(b) 12.5 mm thick OSB conforming to O-2 grade,
(c) 12.7 mm thick OSB conforming to O-1 grade,
(d) 12.7 mm thick waferboard conforming to R-1 grade, or
(e) OSB conforming to 2R32 / 2F16 grade.
(3) Except where the flooring="http://thehandyforce.com/flooring/" title ="Handyman flooring install Toronto">flooring consists of ceramic tiles applied with adhesive, where a separate panel-type underlay or concrete topping is applied to a subfloor on joists spaced not more than 406 mm o.c., the subfloor may consist of not less than,
(a) 12.5 mm thick plywood,
(b) 12.5 mm thick OSB conforming to O-2 grade,
(c) 12.7 mm thick OSB conforming to O-1 grade,
(d) 12.7 mm thick waferboard conforming to R-1 grade, or
(e) OSB conforming to 2R32 / 2F16 grade.
In Plain Language
Subfloor thickness or rating must meet the requirements set out in this article, matched to the joist spacing and anticipated floor loads.
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.