The short answer
Spray foam is an organic plastic, so it can burn, and the products differ in how they react to fire. Some carry fire-retardant additives and a stated fire classification, which the installer should be able to show on the data sheet. The risk in a particular loft depends on the product, the thickness and what is near it, such as cables, chimneys and flues, so check each of those.
What the foam is made of
Spray foam insulation is a polyurethane plastic, made on site by mixing two liquids that expand and set into a foam. Like most plastics, it is combustible. It does not behave like mineral wool or glass fibre, which are made from rock or glass and do not burn in the same way.
That does not make every foam equally hazardous. Products differ in their chemistry and in what is added to them. Many include fire-retardant additives, and manufacturers publish a data sheet with a fire classification for the product. The classification describes how the material behaves in standard laboratory tests, not how it will behave in your loft, where thickness, ventilation and the surrounding construction change the picture.
It also matters whether the foam is exposed or covered. In a roof space, foam on the slopes is usually left uncovered, with nothing between it and the loft. Where building rules require a layer to protect foam from fire, that is the kind of detail an installer and building control should have addressed. Check with your building control body what applied to your loft, as legal advice is outside what we do.
What the data sheet and paperwork should show
The simplest check is to find the paperwork. When foam is installed, there should be a job sheet or certificate naming the product, the thickness and the date. The product itself has a manufacturer's data sheet that states its fire classification and any conditions on its use.
- The product name and type. Open-cell and closed-cell foams are different materials, and the data sheet says which one you have.
- The stated fire performance. Look for a classification and the conditions attached to it, such as use only with a protective covering.
- Thickness applied. A thicker layer can change both insulation and fire behaviour.
- Any installer instructions about clearances around flues, chimneys and fittings.
If you cannot find the paperwork, an inspection can identify the type of foam from its appearance and texture, which helps you find the right data sheet. A foam with no records at all is harder to judge, which is one reason it can complicate a sale. Our answer on whether spray foam is bad places the fire question in the wider picture.
Chimneys, flues and cables
The places where fire risk is most plausible are the ones where heat or electricity is already present. In a roof space these are chimney stacks and breasts, flue pipes, recessed light fittings, cables and any other heat source.
A chimney stack that runs through the loft gets warm in use, and combustible insulation next to it is a matter for care. The usual practice for any insulation near a flue is to keep a clear gap and use non-combustible material around the stack, and the installer should have followed the manufacturer's instructions. If the foam was sprayed up to or around a stack, that deserves a second look.
Cables are the other point. Wiring buried in foam is not easy to inspect, and cables can run warm when they are covered. Recessed downlighters in a ceiling below a foamed roof need to be rated for contact with insulation. These are electrical matters, and an electrician can check them.
A roofer will notice these things during a survey of the roof space, though the electrical checks are for an electrician. If you are concerned about heat sources, mention them when you book. After foam removal the same areas are looked at again, and our answer about the loft after removal follows that stage.
Smoke, fumes and what a fire would mean
When plastics burn they give off smoke and fumes, and foam is no exception. That is one reason a measured view matters: the concern is partly the foam burning and partly what it releases. This is also why smoke alarms matter in any house, and why alarms on every floor, including the landing below a loft, are sensible.
An accurate answer needs the product, and that is where honesty is more useful than reassurance. A new house built with a certified foam system, installed to the manufacturer's instructions, is a different case from an older loft sprayed by an installer who no longer trades. Anyone who tells you foam is entirely safe, or entirely dangerous, has not looked at your loft.
General advice on smoke alarms and escape plans in the home is available on GOV.UK.
Fire, insurers and lenders
Fire is one of several reasons lenders and insurers take an interest in foam. RICS issued its consumer guide in March 2023, and a BBC report dated 20 November 2024 named lenders that refuse foam-insulated houses alongside others that look at each one individually. Your insurer may also want to know about it, so it is worth telling them and keeping the reply. Our answer on selling a house with spray foam covers the paperwork a buyer is likely to ask for.
If you are weighing up removal partly on fire grounds, the figures are typical UK costs of £20 to £50 per square metre, with an average of about £1,500 and disposal at £150 to £400, from MyBuilder's 2026 guide. Your fixed price follows the survey.
A visit from us to inspect the loft costs nothing, and we send photographs afterwards. The service covers Bath and everywhere within 30 road miles, and our spray foam insulation page sets it out in full. If your insurer has asked about the foam, send us their wording before the visit so the photographs cover what they want to see. Call 01225 285181 or use the enquiry form.
