9.23.14.

(1) Subflooring shall be provided beneath finish flooring where the finish flooring does not have adequate strength to support the design loads.

(1) Except as provided in Sentence (2), wood-based panels for subfloors shall conform to,

(a) CSA O121-M, “Douglas Fir Plywood”,

(b) CSA O151, “Canadian Softwood Plywood”,

(c) CSA O153-M, “Poplar Plywood”,

(d) CAN/CSA-O325.0, “Construction Sheathing”, or

(e) CSA O437.0, “OSB and Waferboard”.

(2) Particleboard subflooring may be used only where a building is constructed in a factory so that the subfloor will not be exposed to the weather.

(3) Subflooring described in Sentence (2) shall conform to grade D-2 or D-3 in ANSI A208.1, “Particleboard, Mat-Formed Wood”.

(4) Subflooring described in Sentence (2) shall have its upper surface and all edges treated to restrict water absorption where the subfloor is used in bathrooms, kitchens, laundry rooms or other areas subject to periodic wetting.

(1) Where the edges of panel-type subflooring are required to be supported, such support shall consist of tongue-and-groove panel edges or not less than 38 mm by 38 mm blocking securely nailed between framing members.

(1) Plywood subflooring shall be installed with the surface grain at right angles to the joists and with joints parallel to floor joists staggered.

(2) OSB subflooring conforming to CAN/CSA-O325.0, “Construction Sheathing”, or to O-1 and O-2 grades in CSA O437.0, “OSB and Waferboard”, and waferboard subflooring conforming to R-1 grade in CSA O437.0 shall be installed with the direction of face orientation at right angles to the joists and the joints parallel to the floor joists are staggered.

(1) Except as provided in Sentences (2) and (3), subfloors shall conform to Table 9.23.14.5.A. or Table 9.23.14.5.B.

(2) Where the finished flooring consists of not less than 19 mm matched wood strip flooring laid at right angles to joists, spaced not more than 600 mm o.c., subflooring 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 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 400 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.

(1) When resilient flooring is applied directly to an OSB, waferboard, particleboard or plywood subfloor, the subfloor shall be fastened to the supports with annular grooved nails.

(1) Lumber subflooring shall be laid at an angle of not less than 45° to the joists.

(2) Lumber subflooring shall be fully supported at the ends on solid bearing.

(3) Lumber for subflooring shall be of uniform thickness and not more than 184 mm wide.