Spray foam and lenders
Open-cell foam has been sprayed only over one bedroom. Why can the survey still not see the rafters in that bay?
Not visible in that bay. Open-cell foam sprayed only over one bedroom still covers the rafters there, so the survey cannot see them. The limit is the coated bay, not the whole roof. Open-cell is still a layer on the timber. Calling it open-cell does not make the rafter visible, and limiting it to one bedroom does not let the surveyor inspect the timber under the spray. The other bays may be clear. This bay is not. The report should say the rafters in the foamed bedroom were hidden.
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?
Buyers hope the word open-cell means a lighter product the surveyor can see through. It does not. Where foam coats the underside of the slope, the timber surface is covered, whether the product is open-cell or closed-cell. RICS warns that foam conceals the structure and that an undetected leak can rot timber. That warning does not shrink because only one bedroom was sprayed. A small area is still an area you cannot assess by looking.
Do not average the roof. Write the foamed bay on its own, and describe the unfoamed bays only if they were actually seen. A quotation to remove foam should say what happens to the tiles, because removal can damage the covering. Not every lender refuses foam, so do not invent a policy from the product name. The survey point is narrower and already enough: in the bedroom that was sprayed, the rafters were not available to inspect, and open-cell does not change that.
What should you ask your surveyor?
- Which bay is foamed, and which rafters in it could you see?
- Did open-cell leave any timber surface actually visible?
- What can you say about the unfoamed bedrooms that you cannot say here?
What are the typical next steps?
- Record the foamed bedroom as a bay where the rafters were hidden.
- Do not treat open-cell as see-through.
- Keep the other bays separate if they were inspected bare.
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
Is open-cell acceptable because it is not closed-cell?
No. Open-cell over that bedroom still hides the rafters in that bay. The survey cannot see them, and the product name does not make the timber visible.
Does a single bedroom of foam clear the rest of the roof?
The rest is a different question. This bay stays unseen under the foam, whatever the other bedrooms show, and open-cell does not change that.