Spray foam and lenders
Spray foam covers the rafters so the surveyor could not see the timber. What decay check is blocked, even if the foam itself looks stuck?
The decay check that is blocked is a look at the rafters for rot, beetle and wetting. Spray foam covers the timber, so the surveyor could not see the wood. Foam that looks stuck only shows the face of the foam. It does not show whether the rafter behind is firm, holed or damp. The survey has recorded the concealment. It has not sampled the foam, has not probed the timber through it, and has not said the rafters are sound. Stuck foam is not a decay inspection.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Decay in a roof timber is judged on the wood: soft patches, cuboidal cracking, flight holes, staining, a lost section at the bearing. All of that needs the surface of the timber. Foam sprayed over the rafters takes that surface away. Adhesion of the foam is a comment about the foam. A piece that is firmly stuck can still be stuck to decayed wood, and a piece that is loose can sit over sound wood. The inspection cannot choose between those while the timber stays hidden.
Tell the lender and the solicitor that the rafters were not available to inspect, so no decay check was possible. A specialist may have to remove foam in agreed places if someone needs to see the wood. The home survey has not ordered that removal and has not priced it. Do not gouge the foam on a viewing to steal a look. Until the timber is seen by someone instructed to see it, the decay question stays blocked, however tidy the foam surface appears.
What should you ask your surveyor?
- Which rafters were fully covered so that the timber could not be seen?
- Did a stuck appearance change anything about the hidden wood, or not?
- Have you recorded that no decay check of those rafters was possible?
What are the typical next steps?
- State that the foam blocked any decay check of the rafters.
- Tell the lender the timber itself was not inspected.
- Do not take a stuck surface as proof the wood is sound.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If a rafter end is visible at the wall, is the whole rafter checked?
No. One visible end is only that end. Where foam still covers the rafter, the decay check remains blocked. The survey has not treated a short visible piece as the whole timber. What happens next for the rafterend is outside this note and was not settled here.
Does a dry loft smell clear the hidden rafters?
Smell is not a view of the wood. The surveyor could not see the rafters under the foam, so a dry smell has not cleared them of rot, beetle or wetting. Asking about it again later still leaves this smell point outside what the survey decided.