The Ontario Building Code | Gypsum Board
3.1.5.11. gypsum Board
(1) gypsum board with a tightly adhering paper covering not more than 1 mm thick is permitted in a building required to be of noncombustible construction provided the flame-spread rating of the surface is not more than 25.
In Plain Language
Gypsum board with a thin (1 mm or less), tightly adhered paper covering is allowed in noncombustible-construction buildings provided its surface flame-spread rating doesn't exceed 25.
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.