Spray Foam Insulation Problems: A Homeowner's Guide

What is spray foam insulation, and why is it a concern?

Spray polyurethane foam is sprayed as a liquid onto the underside of a roof, where it expands and sets. In most homes it covers the rafters and the felt or membrane, and in some lofts it has been sprayed straight onto the back of tiles or slates. It was widely sold to UK homeowners, often with promises of lower energy bills or of “stabilising” an older roof.

There are two broad types. Open-cell foam is softer, lighter and more vapour-open. Closed-cell foam is rigid, dense and vapour-resistant, and it bonds very firmly to whatever it touches. Both types change how a roof behaves, and both can make it hard for anyone to see the timbers and roof covering behind them. That combination is why spray foam has become a sticking point in house sales and remortgages.

What problems can spray foam cause?

The issues below do not affect every home, and the severity depends on the type of foam, how well it was installed and the condition of the roof beforehand. Each is worth understanding before you decide what to do.

Condensation and damp

A roof needs to manage moisture. Warm, damp air rises from the house, and in a traditional loft it is carried away by ventilation. Foam that seals the roof slope can change where that moisture ends up. In some lofts condensation forms against or behind the foam, where it cannot dry out. Signs can include damp patches on ceilings below, a musty smell in the loft, mould on exposed timber or water staining around the edges of the foam.

Timber decay risk

Rafters and battens that stay damp for long periods are at risk of rot. The difficulty with spray foam is that the timber is hidden, so decay can develop without anyone noticing. Closed-cell foam in particular can hold moisture tight against wood. Damage is not certain, but it cannot be ruled out without exposing and moisture-checking the timbers.

Hidden roof defects

Foam can cover slipped or cracked tiles, torn felt, broken battens and old leaks. In some cases foam was sprayed onto an already failing roof, which may have held things together for a while but leaves the underlying problem in place. When the foam eventually comes off, those defects are still there and may need a roofer.

Valuations and mortgages

This is the problem that brings most people to us. Many UK lenders and surveyors are cautious about spray foam because they cannot inspect the roof structure behind it. A valuer who sees it may down-value the property, ask for a specialist inspection report, or refuse to lend until it is removed. Equity release lenders are often stricter. Policies vary between lenders and change over time, so you need to check with your own lender or broker. Our page on spray foam and mortgages covers this in more depth.

Roof repairs made harder

Closed-cell foam glued to tiles and felt can make even simple repairs difficult. A roofer may not be able to lift and replace a tile without breaking those around it, and some may be unwilling to work on a foamed roof at all. Tiles and slates that cannot be reused add to the cost of future roof work.

Blocked ventilation

Poorly installed foam can be sprayed right down into the eaves, closing off the gaps that let air move through the loft. Even where the foam itself is sound, blocked eaves ventilation can make condensation more likely in other parts of the roof space.

Smell or poor installation

Some homeowners report a lingering smell after foam has been installed, and some installs are visibly patchy, uneven or incomplete, with gaps, sagging areas or foam over wiring and fittings. A smell is not proof of a problem, and we cannot diagnose it without seeing the loft, but poor workmanship is worth recording and raising with whoever carried out the work.

Mis-selling concerns

Spray foam was often sold door-to-door or by phone, sometimes with strong claims about savings or roof repair. If you feel you were pressured into it, given misleading information, or not told about the possible effect on a future sale, you may want to look into your options as a consumer. Keep any paperwork, contracts, warranty documents and adverts. Free and impartial consumer advice services can help you understand what to do next. We are not able to advise on legal claims, but our written report and photos can form part of your records.

Problems at a glance

How can you check what you have?

You can often learn a lot without going any further than the loft hatch. Use a good torch, stand securely on a proper ladder, and look rather than climb in. Loft floors are often just ceiling joists with plasterboard between them, which will not take your weight, and older lofts may have exposed wiring or sharp fixings.

• Is there foam on the roof slopes? Spray foam usually looks like a lumpy, yellowish or off-white coating over the rafters and between them.
• Soft or hard? If you can safely reach a patch near the hatch, a gentle press with a gloved finger may tell you something. Open-cell foam tends to give slightly; closed-cell feels rigid. Do not pull pieces off.
• How much is covered? Note whether it covers both slopes, the gable walls, the eaves or only part of the roof.
• Any signs of damp? Look for staining, mould, water marks or a musty smell.
• Paperwork? Check for any contract, warranty or invoice from the installer, which may state the foam type and date.

Take a few clear photos from the hatch. They help when you speak to a lender, a broker or a specialist, and they help us understand the loft before a visit.

What should you do next?

1. Get an inspection. A proper look at the foam, the roof slopes and any visible timber tells you the type, extent and likely condition. Our spray foam survey and inspection is a good place to start if you are unsure.
2. Talk to your lender or broker. If you are selling, buying or remortgaging, find out what the lender involved expects. Some will want a specialist report, some will want the foam removed. Only the lender can tell you what they will accept.
3. Decide on removal. If removal makes sense, it is done by hand with scrapers, saws and specialist tools. The foam is bagged and taken away, and the roof underside is cleaned back so the timbers can be seen. Our pages on loft spray foam removal and closed-cell spray foam removal explain the work.
4. Check the roof and timbers. Once exposed, timbers are moisture-checked and the felt, battens and covering are looked at. A roofer may be needed for any repairs.
5. Re-insulate the loft. Most homes are re-insulated at ceiling-joist level with mineral wool, with eaves ventilation kept clear. See re-insulating after removal.

If you are trying to budget for this, our spray foam removal cost guide explains what affects the price and what a written quote should include.

Does it matter what kind of house you live in?

Roof shape and age affect how foam behaves and how hard it is to remove. Victorian terraces across areas such as Walton often have slate roofs and shallow lofts, where foam sprayed straight onto slates is common and access is tight. Inter-war semis in places like Childwall usually have hipped tiled roofs with more slopes and corners. Homes near the coast, for example in Wallasey, are exposed to wind-driven rain, which makes the condition of the roof covering under the foam even more important. Whatever the property, our approach to professional spray foam removal starts with looking properly before recommending anything.

Is spray foam always a problem?

No. Some installations cause no visible issues for years, and not every surveyor or lender reacts the same way. The difficulty is uncertainty: because the foam hides the roof structure, neither you nor a buyer’s surveyor can easily confirm that everything is sound. For many homeowners, that uncertainty is the real problem, especially when a sale or remortgage is on the horizon. An inspection, followed by removal where needed and a written report with photos, gives you something concrete to show the people who make those decisions.