The Ontario Building Code | Attachment to Decking
9.26.11.9. Attachment to Decking
(1) Roofing shall be securely attached to the decking or where insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation is applied above the deck, the insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation shall be securely attached to the deck before the first layer of felt is fastened to the insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation.
In Plain Language
This clause requires roofing to be mechanically fastened to the deck, or, if insulation sits above the deck, the insulation itself must be secured to the deck before the felt underlayment goes down. It's about fastening sequence as much as materials.
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.