The Ontario Building Code | Thickness
9.29.7.2. Thickness
(1) Hardboard shall be not less than,
(a) 3 mm thick where applied over continuous back-up,
(b) 6 mm thick where applied to supports spaced not more than 406 mm o.c., and
(c) 9 mm thick where applied to supports spaced not more than 610 mm o.c.
In Plain Language
This interior finish must meet the minimum thickness set out in this article.
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.