The Ontario Building Code | Thickness
9.29.8.2. Thickness
(1) insulating fibreboard sheets shall be not less than 11.1 mm thick on supports not more than 406 mm o.c.
(2) insulating fibreboard tile shall be not less than 12.7 mm thick on supports spaced not more than 406 mm o.c.
In Plain Language
This clause sets minimum thicknesses for insulating fibreboard used as a wall finish: at least 11.1 mm for sheets on supports up to 406 mm apart, or 12.7 mm for tile on the same support spacing.
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.