Skip to content

“Hot roofs” are not permitted

Over the last few weeks, our inspectors have either encountered building plans that specified site-applied spray foam to the underside of cathedral roofing systems, or talked to contractors in the field who intended to use them.

This is not permitted: all roofing systems, be they using fibreglass, blown-in cellulose, or site-applied spray foam, must be ventilated, with inlets at the lower end of each rafter or truss cavity, and outlets at the top. Further, Code actually mandates that there be a 2.5" (63 mm) gap between the underside of the roof sheathing and the top of the insulation.

More can be found here: