The Ontario Building Code | Combustible Interior Finish

3.1.5.10. Combustible interior Finish

(1) Combustibleinterior finish, including paint, wallpaper, and other interior finishes not more than 1 mm thick, is permitted in a buildingrequired to be of noncombustible construction.

(2) Combustible interior wall finishes, other than foamed plastics, are permitted in a building required to be of noncombustible construction provided they,

(a) are not more than 25 mm thick, and

(b) have a flame-spread rating not more than 150 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction.

(3) Combustibleinterior ceiling finishes, other than foamed plastics, are permitted in a building required to be of noncombustible construction provided they,

(a) are not more than 25 mm thick, except for exposed fire-retardant treated woodbattens, and

(b) have a flame-spread rating not more than 25 on any exposed surface, or on any surface that would be exposed by cutting through the material in any direction, or are of fire-retardant treated wood, except that not more than 10% of the ceiling area within each fire compartmentis permitted to have a flame-spread rating not more than 150.