The short answer
Treat the flag as a request for information. Ask the seller for the installer, product, date and any guarantee, speak to your mortgage provider before going further, and have the roof timbers assessed where they can be reached. Spray foam hides the wood it covers, so the question is what condition the timbers are in beneath it, and that can be answered with a proper inspection.
What the surveyor is telling you
Surveyors flag spray foam in a loft because it changes how the roof can be inspected. Foam sprayed beneath the slates or tiles and over the rafters buries the timber. A surveyor looking from the loft hatch cannot see the wood, cannot test it with a moisture meter, and cannot tell whether the roof covering behind the foam is sound.
That is the reason for the note. The roof is not necessarily failing, and the foam is not automatically headed for removal. It means the report cannot vouch for something it was unable to see. RICS issued consumer guidance in March 2023 that warns of condensation going unchecked and harming parts of the building. Surveyors working to that guide tend to flag any foam they find so that a buyer can make an informed decision.
Read the wording carefully. A line such as "spray foam to the roof slopes, timbers not visible" is a limitation. A line recommending further investigation or specialist advice is a stronger prompt, and a line mentioning damp staining, a musty smell or discoloured timber at the edges of the foam suggests the surveyor saw something that needs attention.
What to ask the seller
Paperwork settles a great deal. Ask the seller for everything that relates to the foam, and ask your solicitor to put the request formally if it is not volunteered.
- Who installed it, and when. The date tells you how long the timbers have been covered.
- Which product was used. The two main foam types differ in how they handle moisture, and the job sheet names which was used.
- Any guarantee or certificate. A guarantee is only as good as the company still standing behind it, so check that the installer is still trading.
- Whether a mortgage or insurance provider was told. Some lenders asked for this at the time of the work, and the answer may affect the sale.
- Any history of leaks, damp or condensation in the loft or the rooms below.
If the seller does not know, that is useful information too. A foam layer with no record of who fitted it, or with what, is harder to assess, and it should weigh on the price or the decision to proceed.
Speak to your lender early
RICS suggests putting one question to your mortgage provider: does its lending policy accept a roof insulated with foam? Do this before you spend money on further reports. A BBC investigation reported on 20 November 2024 found some lenders turning down such properties, while others judged each application on its merits. Lender policy changes, so ask your own provider, or your broker, what they would require on the property you are buying.
A lender may want evidence about the roof timbers, or a recommendation from a surveyor that the foam is acceptable, or in some cases removal before completion. Knowing that early stops a purchase stalling days before exchange. Our guide to spray foam and roof timbers explains what an inspection looks at, which is the evidence lenders and surveyors are usually looking for.
The RICS guide itself is on the RICS website.
Getting the timbers checked
If the foam has been flagged and the lender is willing to proceed, a roof assessment is the usual next step. It usually involves a visual inspection of the loft, moisture readings on the exposed timber at the edges of the foam, a check of the gable ends and eaves, and sometimes small sample cuts into the foam to expose a patch of wood. Typical UK assessment costs are around £100 to £200, according to MyBuilder's 2026 spray foam removal guide. If work follows, the price you receive after the survey is a firm figure.
An inspection can come back in three ways. The timbers may be dry and sound, in which case the foam can stay, with the findings on file for the next buyer. Moisture may be present at one point, such as a leaking valley or an eaves detail, which can be put right without disturbing the rest. Or the timber may be damp or decayed across a large area, which is the case where removal is usually discussed.
Roofing is where our interest lies. We look at the roof covering, the lead work, the underlay and the timbers together, because a damp rafter is often caused by a defect in the covering above it and not by the foam alone. You can see how spray foam interacts with the covering on our page about spray foam and damage to slates and tiles.
Options for buyer and seller
Once the facts are in, there are usually four routes. None of this is legal advice, and your solicitor should guide the contractual side.
- Proceed. Sound timbers and a relaxed lender mean the sale can carry on with the assessment attached to the file.
- Renegotiate. The buyer can ask for money off to cover an assessment and any removal, and the seller may agree to keep things moving.
- Remove before exchange. A seller can have the foam taken off and the roof put right, so the buyer inherits a loft that can be inspected.
- Step back. Where the survey and timber findings point to wider defects, walking away is a legitimate choice.
On energy performance, foam has a reputation for good insulation, and there is a separate question of how much it saves in practice, covered in our answer on whether spray foam saves energy. A buyer weighing up removal may want to balance the loss of that insulation against the risk to the roof, then plan replacement insulation that lets the roof breathe.
If removal is the answer
Spray foam removal is slow, careful work, because the foam is stuck hard to the covering and the timbers. Typical UK costs run at £20 to £50 per square metre, averaging about £1,500 for a typical loft, with disposal on top at £150 to £400, according to MyBuilder's 2026 guide. Price moves with loft size, foam type, how the wood behind it has fared, and what must follow in terms of insulation and membrane. Your fixed quote follows the survey.
We inspect the loft free of charge and send pictures of it, so buyer and seller argue from the same evidence. If the sale has a deadline, tell us the exchange date at the outset so the removal and the timber report reach the solicitors in time. Whether you are buying or selling in Bath or within 30 road miles of it, call 01225 285181 or send the enquiry form and we will arrange the survey. For the service as a whole, start at our spray foam insulation hub.
