Spray foam and lenders
The loft quilt is already about 300 millimetres deep. Does the survey require spray foam as well so the roof can pass?
No. A home survey does not set a legal depth of insulation, and it does not require spray foam on top of a quilt so the roof can pass. About 300 millimetres of quilt, if that is what is there, is a description of the loft, not a fail. Foam under the tiles is a different product, so do not install it to satisfy a report that has not asked for it.
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?
RICS’s spray-foam guide compares the decision to foam a roof with the simpler step of topping up a loft quilt, and it explains the inspection and moisture problems foam can cause. It does not publish a legal thickness that a buyer must hit, and a surveyor does not fail a house because a tape measure shows a different number. If the quilt is already deep, the survey might say nothing about it, or it might note ventilation and the storage that squashes it. Those comments are not an order to spray the underside of the tiles. Inventing a required depth and then selling foam as the way to reach it misuses the report.
Ask the surveyor, if the loft is mentioned at all, whether they could see the rafters and whether any foam was present. If the rafters are bare and the quilt is deep, you do not add foam to make the survey happier. There is no such requirement to meet. A lender’s valuation is not a building-regulations energy calculation either. If you later choose to improve insulation, a further quilt is the comparison RICS points to, and even then the survey has not specified a product. Do not let an installer quote foam against a sentence the report does not contain.
What should you ask your surveyor?
- Did you see foam anywhere, or only quilt on the loft floor?
- Are you setting a minimum depth? Please confirm you are not.
- Could you inspect the rafters, and did anything stop you?
What are the typical next steps?
- Do not buy spray foam to satisfy a survey that has not asked for it.
- If you want more insulation later, do not start from a fake legal depth.
- Tell any installer the survey does not require foam over a deep quilt.
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 300 millimetres a regulation the survey is enforcing?
No. It is the depth in the question. The survey does not turn a tape reading into a law, and it does not fail a different depth by itself.
Does a thin quilt mean you must use foam?
No. A thin quilt, if the survey mentions it, is a description. Foam is not the compulsory upgrade. RICS points to the problems foam can cause under the covering.