m Ransley wrote:
Why did you buy warped boards, use roofing cap nails or screw and
washer if needed glue. Drywall over foam, foam is not a good support it
gives, if you want a good job and are taping you need solid support to
wood like 1x2 strips nailed to plywood and foam cut to insert inbetween
the furring strips. The foam itself is a vapor barrier even wthout the
foil.



Find 'roofing tins' really thin ~2 inch diameter circles designed to be
nailed right thru. I did this exact thing almost 20 years ago. I drilled
the tins in stacks[1200 sqft to nail] because the foam is soft enough
you punch through.

Furring strips is a good idea, more as it adds another airspace for
insulation