Roof timber rot from trapped moisture
Why it happens here
Foam sprayed onto the underside of felt blocks the eaves gap, so moisture from the house cannot escape. Heslington's older roofs were not designed for that. After two or three winters, the battens and rafter ends start to soften.
Our approach
We remove the foam, check every rafter with a moisture meter, and replace any timber that has already gone. Then we restore the ventilation path so the roof can dry out properly.