Closed cell foam locking down the roof structure
Why it happens here
Closed cell polyurethane foam sets rigid and bonds hard to the rafters and felt. On a shallow 1970s trussed roof, that stops the roof moving and breathing the way it was designed to. Moisture gets trapped and the timbers stay wet.
Our approach
We cut the foam out in sections rather than pulling it, which avoids cracking the rafters or tearing the felt. Dry ice blasting then lifts the residue so the timber can dry naturally. We check ventilation paths before we leave.