(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.
(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 610 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 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.