The Ontario Building Code | Noncombustible Materials
3.1.5.1. Noncombustible Materials
(1) Except as permitted by Sentences (2) to (4) and Articles 3.1.5.2. to 3.1.5.25., 3.1.13.4. and 3.2.2.16., a building or part of a building required to be of noncombustible construction, shall be constructed with noncombustible materials.
(2) Notwithstanding the definition for noncombustiblematerials stated in Article 1.4.1.2. of Division A, a material is permitted to be used in noncombustible construction provided that, when tested in accordance with CAN/ULC-S135, "Test Method for the Determination of Combustibility Parameters of Building Materials Using an Oxygen Consumption Calorimeter (Cone Calorimeter)", at a heat flux of 50 kW/m2,
(a) its average total heat release is not more than 3 MJ/m2,
(b) its average total smoke extinction area is not more than 1.0 m2, and
(c) the test duration is extended beyond the time stipulated in the referenced standard until it is clear that there is no further release of heat or smoke.
(3) If a material referred to in Sentence (2) consists of a number of discrete layers and testing reveals that the surface layer or layers protect the underlying layers such that the complete combustion of the underlying layers does not occur, the test shall be repeated by removing the outer layers sequentially until all layers have been exposed during testing, or until complete combustion has occurred.
(4) The acceptance criteria for a material tested in accordance with Sentence (3) shall be based on the cumulative emissions from all layers, which must not exceed the criteria stated in Clauses (2)(a) and (b).
In Plain Language
Buildings or parts required to be of noncombustible construction generally must use noncombustible materials, but this clause allows an alternative path: a material can still qualify if cone-calorimeter testing under CAN/ULC-S135 shows it releases limited heat and smoke within set thresholds, even if it wouldn't otherwise meet the strict noncombustible material definition.
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.