The Ontario Building Code | Protection of Foamed Plastics
3.1.4.2. Protection of Foamed Plastics
(1) Foamed plastics that form part of a wall or ceiling assembly in combustible construction shall be protected from adjacent spaces in the building, other than adjacent concealed spaces within attic or roof spaces, crawl spaces, and wall assemblies,
(a) by one of the interior finishes described in Subsections 9.29.4. to 9.29.9.,
(b) by any thermal barrier that meets the requirements of Sentence 3.1.5.12.(2), or
(c) where the buildingdoes not contain a Group B or Group C major occupancy, by sheet metal,
(i) mechanically fastened to the supporting assembly independent of the insulation,
(ii) not less than 0.38 mm thick, and
(iii) with a melting point not below 650°C.
(2) The flame-spread rating on any exposed surface of combustible insulation, or any surface that would be exposed by cutting through it in any direction, shall be not more than 500.
In Plain Language
Foamed plastic insulation in combustible-construction walls or ceilings must be separated from adjacent spaces by an approved interior finish, a compliant thermal barrier, or (in buildings without Group B/C occupancies) protective sheet metal, and any exposed or cut surface of that insulation is capped at a flame-spread rating of 500.
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.