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.