Spray foam and lenders
What should you ask if spray foam in a loft runs up to a party wall or into a neighbour’s roof space?
Ask whether the foam crosses the boundary line, and do not treat it as only your loft. In a terrace the roof space may be separated poorly. Foam sprayed across a party line is a neighbour and fire-separation question as well as a timber question. A home survey sees your loft. It may not be able to say what was done next door.
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 warns that polyurethane spray foam is combustible and can increase the spread of a fire if it is used in the wrong place. That is not a statement that your house will burn. It is a reason to know where the foam is. A party wall is also a legal boundary. GOV.UK’s party-wall guidance is about work the building owner intends to do. Foam already sprayed is a fact on the ground. Your solicitor asks about the boundary. The survey describes the foam it could see.
Do not cut back foam on the party line yourself. Ask the surveyor how far it goes, and ask a roofer or a competent person about fire separation if the wall head is buried. If a lender is involved, show them the location, not only the word “foam”. There is no standard price for removing a strip at the party wall.
What should you ask your surveyor?
- Does the foam stop at the party wall, or run through?
- Could you see the wall head at all?
- Is fire separation part of your comment, or only the covering?
What are the typical next steps?
- Tell your solicitor if the foam appears to cross the boundary.
- Do not rely on the neighbour to remove it without asking.
- If you need it gone, include the party line in the roofer’s scope so they do not stop at the easy part.
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
Does RICS ban foam on party walls?
The guide does not use those words. It warns about fire performance and about hidden defects. The detail is for the lender and the person who can see the wall.
Is a masonry party wall a fire stop by itself?
It can be the separation, if it is complete to the underside of the covering. Foam hiding the head means the surveyor could not confirm that. Ask.