(1) Except as provided in Sentences (2) and (4), foamed plastics that form part of a wall or ceiling assembly shall be protected from adjacent space in the building, other than adjacent concealed spaces within attic or roof spaces, crawl spaces, wall assemblies and ceiling assemblies, by any of the following:
(a) one of the finishes described in Subsections 9.29.4. to 9.29.9.,
(b) provided the building does not contain a Group C major occupancy, sheet metal that,
(i) is mechanically fastened to the supporting assembly independent of the insulation,
(ii) is not less than 0.38 mm thick, and
(iii) has a melting point not less than 650°C, or
(c) any thermal barrier that meets the requirements of Sentence 3.1.5.15. (2).
(2) A walk-in cooler or freezer consisting of factory-assembled wall, floor or ceiling panels containing foamed plastics is permitted to be used, provided the panels,
(a) are protected on both sides by sheet metal not less than 0.38 mm thick having a melting point not less than 650°C,
(b) do not contain an air space, and
(c) have a flame-spread rating that is not more than that permitted for the room or space in which they are located or that they bound.
(3) The flame-spread rating of panels required in Clause (2) (c) shall be determined by subjecting a sample panel with an assembled joint typical of field installation to the applicable test described in Subsection 3.1.12.
(4) Thermosetting foamed plastic insulation having a flame-spread rating of not more than 200 is permitted to be used in factory-assembled doors in storage garages serving buildings of residential occupancy provided that,
(a) the insulation is covered on the interior with a metallic foil,
(b) the assembly has a surface flame-spread rating of not more than 200, and
(c) the assembly incorporates no air spaces.