Roof rot from trapped moisture under closed cell foam
Why it happens here
Closed cell foam is effectively a waterproof layer. When it is sprayed directly onto tile felt in an older East Croydon roof, any moisture that gets in cannot escape. Over two or three winters, rafters and battens start to decay.
Our approach
We remove the foam with dry ice blasting or a cutting saw, inspect every rafter with a moisture meter, and treat or replace anything that has started to rot. Then we restore ventilation so the roof can dry out properly.