The Ontario Building Code | Combustible Components for Exterior Walls
3.1.5.5. Combustible Components for exterior Walls
(1) Except as required by Sentence (2), an exterior non-loadbearing wall assembly that includes combustible components is permitted to be used in a building required to be of noncombustible construction provided,
(a) the buildingis,
(i) not more than 3 storeys in building height, or
(ii) not more than 6 storeys in building height ifsprinklered,
(b) the interior surfaces of the wall assembly are protected by a thermal barrier conforming to Sentence 3.1.5.12.(3), and
(c) the wall assembly satisfies the criteria of Sentences (3) and (4) when subjected to testing in conformance with CAN/ULC-S134, "Fire Test of Exterior Wall Assemblies".
(2) Except as permitted by Articles 3.2.3.10. and 3.2.3.11., where the area of unprotected openings determined in accordance with Tables 3.2.3.1.B. to 3.2.3.1.E. is required to be not more than 10% of the exposing building face, the construction requirements of Table 3.2.3.7. shall be met.
(3) Flaming on or in the wall assembly shall not spread more than 5 m above the opening during the test procedure referenced in Sentence (1).
(4) The heat flux during the flame exposure on a wall assembly shall be not more than 35 kW/m2 measured 3.5 m above the opening during the test procedure referenced in Sentence (1).
(5) A wall assembly permitted by Sentence (1) that includes combustiblecladding of fire-retardant treated wood shall be tested for fire exposure after the cladding has been conditioned in conformance with ASTM D2898, "Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing".
(6) The requirements in this Article do not apply where foamed plastic insulation is used in an exterior wall assembly of a buildingand the insulation is protected in conformance with Sentences 3.2.3.8.(1) and (2).
In Plain Language
Exterior non-loadbearing walls with combustible components are allowed on noncombustible-construction buildings up to 3 storeys (or 6 storeys if sprinklered), provided the wall's interior surface has a compliant thermal barrier and the assembly passes the CAN/ULC-S134 exterior wall fire test, with additional restrictions where unprotected opening area limits apply.
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.