How the two foam types differ and why the answer shapes what happens next.
Spray foam in a roof falls into two broad types, and the type decides a good deal about how the foam behaves.
Open-cell foam is soft and spongy, and it lets moisture pass through it more easily. It is usually lighter in colour and easier to cut away.
Closed-cell foam is denser and harder, and it bonds firmly to what it is sprayed on. It resists moisture passing through, which can leave damp trapped against the timber if water gets in from another direction.
Knowing which type you have affects how the roof timbers are likely to fare and how much work removal would involve.
Related: Spray foam roof survey
