The Ontario Building Code | Metal Roof Deck Assemblies
3.1.14.2. Metal Roof Deck Assemblies
(1) Except as permitted by Sentence (2), a metal roof deck assembly shall meet the conditions of acceptance of CAN/ulc-S126, "Test for Fire Spread Under Roof-Deck Assemblies", if,
(a) it supports a combustible material above the deck that could propagate a fire beneath the roof deck assembly, and
(b) the deck is used to comply with the requirements of Sentences 3.2.2.25.(2), 3.2.2.32.(2), 3.2.2.53.(2), 3.2.2.59.(2), 3.2.2.70.(2) and 3.2.2.76.(2) for noncombustible construction.
(2) The requirements of Sentence (1) are waived provided,
(a) the combustiblematerial above the roof deck is protected,
(i) by not less than 12.7 mm thick gypsum board, mechanically fastened to a supporting assembly if located beneath the roof deck, or
(ii) by a thermal barrier conforming to one of Clauses 3.1.5.12.(2)(c) to (e) that is located on the underside of the combustible material or beneath the roof deck,
(b) the buildingis sprinklered, or
(c) the roof assembly has a fire-resistance rating not less than 45 min.
3.1.15. Roof Covering
In Plain Language
Metal roof deck assemblies generally must pass the CAN/ULC-S126 fire-spread test if they support combustible material above the deck capable of propagating fire and are being used to satisfy noncombustible-construction provisions, though this is waived if the combustible material above is adequately protected as described in Sentence (2).
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.