The Ontario Building Code | Thickness

9.27.9.2. Thickness

(1) Type 1 or 2 hardboard cladding shall be not less than,

(a) 6.0 mm thick when applied over sheathing that provides continuous support, and

(b) 7.5 mm thick when applied to furring or framing members not more than 406 mm o.c.

(2) Type 5 hardboard cladding shall be not less than 9.0 mm thick when applied over sheathing that provides continuous support or over furring or framing members spaced not more than 406 mm o.c.

(3) Where hardboard cladding is grooved, the grooves shall not extend more than 1.5 mm into the minimum required thickness.