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Solution that will allow me to spray foam sloped part of roof and dormer roof mid-construction

Mill_house | Posted in General Questions on

Climate zone 7 Canadian Prairie unvented unconditioned attic cape cod style house, 1940s
I want to have the sloped portion of the roof spray foamed prior to winter.  The problem I’m having is figuring out a way to have the work done knowing that in the spring portions of my roof sheathing will be removed to lay plywood (I’m having eave extensions added – approx. 3 feet of existing roof sheathing will be removed around perimeter and to allow for plywood tie in).
Can you think of what I can insert on the underside of the room sheathing that will allow them to spray foam?  I’m only having 3″ of spray foam as rafters are only 2×4 fir.  While inadequate, I am not replacing them.

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  1. GBA Editor
    Martin Holladay | | #1

    You can install rectangular strips of asphalt felt or cardboard in each rafter bay, covering the underside of the roof sheathing before the spray foam contractor shows up. That's labor-intensive work, but it will prevent the spray foam from gluing everything together.

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