Quick answer: Spray foam on the underside of a roof can make a property harder to value, sell or remortgage, because it hides the roof timbers from inspection and, if badly installed, can trap moisture against them. RICS says its presence can affect a surveyor's opinion of value and that a specialist report may be requested. Not every installation is a problem, but if a lender or surveyor has raised it, or you can see signs of damp, removal and re-insulating properly is one option.
For many Cardiff and South Wales homeowners, spray foam only becomes an issue when a survey comes back or a mortgage offer is held up. It is a stressful position to be in. This guide sets out what the guidance actually says, without scaremongering, and what removal involves if that is the route you take.
What is spray foam insulation?
Spray foam is a polyurethane foam sprayed onto the underside of the roof, usually between and over the rafters, where it expands and sets. RICS notes it has often been marketed as an easy fix, but it treats installation as a significant alteration to a home.
There are two main types. The Energy Saving Trust explains that closed-cell foam is a very effective insulator but is not vapour permeable, so moisture that gets in can't easily escape. Open-cell foam is more breathable and lighter but a weaker insulator, so it needs to be thicker.
Why spray foam causes survey and mortgage problems
The timbers can't be inspected
RICS, the professional body for surveyors, notes in its consumer guide that if the timber roof structure is covered with spray foam, it cannot be fully seen or inspected. A surveyor can't confirm the condition of rafters, battens or the underside of the roof covering if they are hidden behind foam.
Moisture can be trapped
Spraying foam directly onto the roof changes a cold, ventilated loft into a warm roof. RICS warns that it will seal in moisture unless adequate precautions are taken, and that an undetected roof leak can lead to rotting timber. The Energy Saving Trust gives the same warning, and says the highest risk is vapour-impermeable foam sprayed directly onto an old and poorly maintained roof.
Repairs become harder
Both organisations point out that repairs are more difficult once timbers are coated in foam. RICS mentions storm damage being harder to repair, and the Energy Saving Trust notes that foam-coated timbers are more difficult to replace.
Lenders and valuers are cautious
RICS states that the presence of spray foam is a factor that could affect a surveyor's professional opinion of value, and that the surveyor may ask for an independent specialist report. Surveyors also have to follow the policies of the lender instructing them. When RICS launched its consumer guide in March 2023, it noted that concern had started in parts of the lending market such as equity release and was affecting lenders more widely.
Keeping it in perspective
It is worth being clear about what the guidance does not say. It does not say every spray foam installation is dangerous or that every lender will refuse a property with it. The Energy Saving Trust says that mortgage difficulties were a real issue for a while, and that industry work since then should make things easier for properly installed foam. In 2023 the Property Care Association and the Residential Property Surveyors Association also published an inspection protocol, giving surveyors a framework for non-invasive visual inspection of spray foam in pitched roofs.
In practice, what happens depends on the type of foam, how and when it was installed, the condition of the roof, what paperwork you have, and the policy of the specific lender. If you are not sure where you stand, an independent survey is a sensible first step before deciding to remove anything.
What paperwork helps
RICS recommends that homeowners keep the documentation from the installer, including the contract, calculations, any guarantee or warranty, and independent product certificates such as BBA or Kiwa. It also recommends keeping photos and records of the roof and moisture readings. If you have this paperwork, find it before you speak to a lender or surveyor. If you don't, that can be part of why removal gets recommended.
Signs your spray foam may be causing problems
- Damp patches, staining or dark marks on timbers at the edges of the foam
- A musty or damp smell in the loft
- Mould on stored items or on exposed timber
- Foam cracking, shrinking or pulling away from the rafters
- Water dripping or staining on the ceilings below after rain
- Foam sprayed into the eaves, blocking ventilation
- Foam sprayed directly onto the back of tiles or slates with no membrane between
- Slipped or broken tiles that are hard to repair because they are bonded in foam
None of these proves the timbers are damaged, but they are a reason to get it looked at. If you are seeing condensation or mould elsewhere in the loft, our guide to loft condensation and mould may help.
How spray foam removal works
Removal is a careful, physical job. RICS describes spray foam as not considered reversible because removing it could potentially damage the existing structure, and the Energy Saving Trust notes that you might need to replace parts of the structure it was applied to. We tell customers that honestly up front: removal is usually very achievable, but we can't promise what we will find until the foam is off.
- Survey. We inspect the loft, identify the type of foam where we can, look at how it has been applied, check accessible timbers and the roof covering, and agree a scope and price with you.
- Protection. The loft hatch, landing and route out of the house are protected, and the loft floor is covered.
- Removing the foam. The foam is cut and scraped back from the rafters, battens and underlay by hand, taking care not to disturb the roof covering more than necessary.
- Cleaning the timbers. Residue is cleaned off the rafters so they can be properly inspected.
- Inspection and recording. Once exposed, the timbers are checked for damp, rot and damage, and photographed. Anything that needs repair is discussed with you before any extra work is done.
- Waste removal. All foam is bagged and taken away.
- Re-insulating properly. The loft is re-insulated in a way that suits the roof, usually mineral wool at joist level with ventilation restored, or another method if the loft space is used.
What affects the cost of removal
We price spray foam removal after a survey, because the jobs vary a great deal. The main factors are:
- The area of roof covered and how thick the foam is
- Whether it is open-cell or closed-cell foam, which affects how easily it comes away
- Whether it is sprayed onto a membrane or directly onto the back of tiles or slates
- Access, headroom and how much is stored in the loft
- The condition of the timbers once exposed, and whether any repairs are needed
- Re-insulation, boarding and any other work done at the same time
- Waste volume and disposal
What to ask any removal company for
If the reason for removal is a mortgage or sale, the paperwork matters as much as the work. Ask for:
- Before, during and after photos of every roof slope, clearly showing the exposed timbers
- A written report describing what was removed, the condition of the timbers, and any repairs carried out
- Confirmation that all foam has been removed, including from the eaves and around the edges
- Details of the re-insulation fitted afterwards
- Confirmation of how the waste was disposed of
Check with your lender or surveyor what evidence they want to see before work starts, so the report covers it. And as RICS advises, be wary of cold calls or unsolicited offers, including offers to remove foam.
Talk to us
If you have spray foam in your loft and a survey or lender has raised it, we can look at it, explain your options honestly and, if removal is the right call, price it clearly. Read more about our spray foam removal service or request your free survey. You can also call 0800 229 4668.