Notes to Table 3.1.3.1.:
3.1.5.12. Combustible Insulation (1) Foamed plastic insulation shall conform to Article 3.1.5.12A. (2) Combustible insulation with a flame-spread rating not more than 25 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in a building required to be of noncombustible construction. (3) Combustible insulation is permitted to be installed above roof decks, outside of foundation walls below ground level and beneath concrete slabs-on-ground of buildings
required to be of noncombustible construction. (4) Except as provided in Sentences (5) and (6), combustible insulation with a flame-spread rating more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in a building required to be of noncombustible construction, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier consisting of, (a) not less than 12.7 mm thick gypsum board mechanically fastened to a supporting assembly independent of the insulation, (b) lath and plaster, mechanically fastened to a supporting assembly independent of the insulation, (c) masonry, or (d) concrete. (5) Combustible
insulation with a flame-spread rating more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in the exterior walls of a building required to be of noncombustible construction, that is not sprinklered and is more than 18 m high, measured from grade to the underside of the roof, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier that, (a) consists of gypsum board not less than 12.7 mm thick, mechanically fastened to a supporting assembly independent of the insulation and with all joints either backed or taped and filled, (b) consists of lath and plaster, mechanically fastened to a supporting assembly independent of the insulation, (c) consists of masonry or concrete not less than 25 mm thick, or (d) when tested in conformance with CAN/ULC-S101, “Fire Endurance Tests of Building Construction and Materials”, does not develop an average temperature rise more than 140°C or a maximum temperature rise more than 180°C at any point on its unexposed face within 10 min. (6) Combustible
insulation with a flame-spread rating more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in the interior walls, within ceilings and within roof assemblies of a building required to be of noncombustible construction, that is not sprinklered and is more than 18 m high, measured from grade to the underside of the roof, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier that, (a) consists of Type X gypsum board not less than 15.9 mm thick, mechanically fastened to a supporting assembly independent of the insulation and with all joints either backed or taped and filled, conforming to, (i) ASTM C1177 / C1177M, “Glass Mat Gypsum Substrate for Use as Sheathing”, (ii) ASTM C1178 / C1178M, “Coated Glass Mat Water-Resistant Gypsum Backing Panel”, (iii) ASTM C1396 / C1396M, “Gypsum Board”, (iv) ASTM C1658 / C1658M, “Glass Mat Gypsum Panels”, or (v) CAN/CSA-A82.27-M, “Gypsum Board”, (b) consists of non-loadbearing masonry or concrete not less than 50 mm thick, (c) consists of loadbearing masonry or concrete not less than 75 mm thick, or (d) when tested in conformance with CAN/ULC-S101, “Fire Endurance Tests of Building Construction and Materials”, (i) does not develop an average temperature rise more than 140°C or a maximum temperature rise more than 180°C at any point on its unexposed face within 20 min, and (ii) remains in place for not less than 40 min.