Spray foam and lenders

What does RICS say about topping up loft quilt compared with installing spray foam?

RICS says topping up existing mineral wool is likely to be substantially cheaper than installing spray foam, and that energy-saving claims may not be achieved if foam is not planned properly. That is a comparison the guide is willing to make. It is not a quote for your loft, and it is not a reason to rip foam out before a lender has asked you to.

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?

Quilt on the loft floor and foam under the slope do different jobs and create different inspection problems. Quilt does not stick to the rafters, so a surveyor can still lift a corner, which is what the Level 3 description says the surveyor will do where it is safe. Foam can remove that option. The cost comparison in the guide is about installation choices, not about the cost of reversing a job that has already been done.

If the house already has foam, the cheap quilt option is no longer the question in front of you. The question is documentation, what the surveyor could see, and the lender’s policy. If the house has a thin quilt and no foam, do not let a seller talk you into foaming the slope as a condition of sale without reading the RICS guide and asking the lender first.

What should you ask your surveyor?

Is there quilt, foam, or both, and which timbers can you still see?
Are you able to lift any insulation, or has foam made that impossible?
What should a buyer ask a lender before adding foam to a roof that does not have it?

What are the typical next steps?

If you are the buyer of a quilted loft, do not agree to a foam installation before completion.
If foam is already there, follow the document pack and the lender, not the quilt comparison.
Do not use “substantially cheaper” as a figure in a price negotiation. RICS did not publish a price.

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 thicker quilt always beat foam for heat loss?

The guide warns that energy claims fail when the installation is not planned, and it points to quilt as likely cheaper. It does not give this roof a U-value. An EPC is not that calculation either.

Can you lay quilt over foam?

Not sensibly, if the foam is on the slope and the quilt belongs on the flat ceiling. Ask a designer before you pile products on top of each other.