12 May, 2026/ by Surveyor Local /Guides, Property defects
Spray foam insulation has gone from being a government-backed energy efficiency measure to one of the most contentious issues in UK property surveys. Its presence in a loft can prevent a mortgage provider from offering finance, stop the survey from properly assessing the underlying timber structure and, in some cases, cause significant hidden damage to the timbers beneath. For an overview of all issues a survey can flag, see our common survey problems guide.
Here, Surveyor Local looks at what spray foam insulation is, why it causes problems, how surveys identify it, what foam removal costs and what it means if it is flagged on your report.
Quick summary
- Spray foam insulation is a liquid polyurethane product that expands and hardens on application, creating a seal in loft spaces and wall cavities.
- It was promoted under government energy efficiency schemes but its use in loft spaces has since been found to cause ventilation problems, timber decay and access issues.
- Both Level 2 and Level 3 surveys will identify the presence of foam insulation. The timbers beneath it cannot be inspected.
- Many mortgage lenders will decline to lend on buildings where foam is present until a specialist assessment has been completed, and some require removal as a condition of lending.
- Removal costs range from £20 to £30 per square metre for open-cell foam and £30 to £50 per square metre for closed-cell foam.
- If you are considering buying a building with spray foam insulation, specialist assessment and mortgage advice are both essential before you proceed.
What is spray foam insulation?
Spray foam insulation is a liquid polyurethane product applied to walls, floors and loft spaces using a spray gun. It expands instantly on contact with the surface, filling gaps and sealing joints, then solidifies into a hard layer of insulation. Its appeal has been its ability to cover irregular surfaces quickly and comprehensively.
There are two types. Open-cell spray foam is softer and semi-permeable, allowing water vapour to pass through it. Closed-cell spray foam is hard, dense and impermeable, creating a complete vapour barrier. The distinction matters because closed-cell foam causes more significant problems in loft spaces and is more expensive and difficult to remove.
For a period, spray foam insulation was included in government-backed energy efficiency grant schemes, including the Green Homes Grant Voucher Scheme, which closed to new applications in March 2021. As a result, a significant number of UK buildings had spray foam applied during that period. According to a jointly-prepared submission to HM Government from the Property Care Association and the HomeOwners Alliance in May 2025, an estimated 35% of a sample of 500 assessed buildings had some form of defect attributable to spray foam installation.
If you see spray foam in a loft during a viewing, it does not have to be an immediate deal-breaker, but it will raise serious questions that need answering before you proceed.
Problems caused by foam in loft spaces
The Royal Institution of Chartered Surveyors (RICS) has stated that the application of spray foam insulation should be treated not as a straightforward fix but as "a significant and fundamental alteration to the home which needs careful consideration and planning." In practice, it has caused several well-documented problems.
Ventilation and condensation
The hard seal created when spray foam is applied to the underside of the timbers prevents air circulation within the loft. Without adequate ventilation, moisture builds up and condensation forms on the timbers. The foam then traps that moisture rather than allowing it to escape, particularly during colder months. Over time this causes timber rot and, if left untreated, can eventually threaten the structural integrity of the building.
Hidden defects
Because spray foam bonds directly to the timbers and roof coverings, a survey cannot assess the state of the underlying structure. Rot, insect damage or other defects may be present but impossible to identify without foam removal. This unknown is the core reason mortgage lenders are reluctant to proceed.
Inconsistent workmanship
The quality of foam installation has been highly variable. Some installations were carried out without adequate preparation, in unsuitable conditions or using products not appropriate for the specific building construction. Poor workmanship accelerates the problems described above and makes assessment even more difficult.
Damage on removal
Spray foam bonds strongly to tiles, battens and timbers. Removal, particularly of closed-cell foam, carries a risk of cracking tiles and damaging the underlying structure. Any removal project should therefore be budgeted to include potential remedial repairs on top of the foam removal cost itself.
Will a survey detect foam insulation?
Yes. A chartered surveyor carrying out a Level 2 or Level 3 building survey will identify the presence of foam insulation during their inspection of the loft, and will attempt to determine from visual inspection whether it is open-cell or closed-cell.
What the survey cannot do is inspect the timbers and underlying structure beneath the foam. This limits the ability to assess the timber structure and means the report will note this as an area of uncertainty.
RICS Level 2 survey: the foam insulation will be flagged, the mortgage implications noted and a specialist assessment recommended.
RICS Level 3 survey: the presence will be confirmed and potential issues assessed in more detail. A specialist assessment will again be recommended. The more thorough inspection may allow wider comment on the building's overall state, but the timbers beneath the foam will remain inaccessible.
In both cases, the report will recommend that your conveyancing solicitor obtains any available installation certification. Where it was properly installed, the installer should have provided BBA (British Board of Agrément) or KIWA certification. Without this documentation, the position for both mortgage lenders and insurers becomes significantly more difficult.
Not sure which survey is right for your property? Compare RICS surveys.
Foam removal costs
Where foam removal is recommended or required as a condition of a mortgage offer, costs depend on the type of foam, the size of the loft space, the accessibility of the area and the extent of any damage found during the removal process.
Open-cell foam is softer and easier to remove. Closed-cell foam is harder, bonds more aggressively and carries a greater risk of collateral damage to the underlying structure.
As a rough guide, current UK removal costs are:
- Open-cell foam: £20 to £30 per square metre
- Closed-cell foam: £30 to £50 per square metre
These figures do not include any remedial repairs to timbers, tiles or flashings damaged during removal, scaffolding where required, waste disposal or the certification issued on completion. The completion certificate is worth factoring in as a line item, since it will be required by mortgage lenders and any future buyer.
Always use a certified specialist and obtain at least three quotes. The cheapest is not always the best choice for work of this nature, where the quality of foam removal and the documentation issued on completion both matter.
Can you get a mortgage with spray foam insulation?
This is the question most buyers are asking. The short answer is: possibly, but it is complicated.
Most mortgage lenders are unwilling to lend on a building where spray foam is present, because the survey cannot inspect the underlying timber structure and the lender cannot be confident of the state of the asset securing their loan. The uncertainty itself is the problem.
Some lenders will consider a case-by-case approach where the seller can provide:
- The original BBA or KIWA installation certificate
- Evidence of ongoing maintenance in line with the manufacturer's requirements
- A satisfactory specialist assessment of the current state
Even where a lender is willing to proceed on this basis, they may require the buyer to commission and pay for the specialist assessment as a condition of the mortgage offer.
Where none of this documentation is available, or where a specialist assessment identifies problems, most lenders will require foam removal before they will lend. A mortgage broker with experience in this area is worth consulting early, as product availability varies considerably between lenders and the landscape is still evolving.
Get spray foam identified before you commit
A RICS Level 2 or Level 3 survey is the right first step for any property purchase. Get a free quote or call our friendly team on .
Frequently asked questions
I can see foam in the loft. Is this a deal-breaker?
Not automatically, but it requires careful handling. The key questions are whether installation certification exists, what type of foam was used and whether a lender willing to proceed can be found. A specialist assessment before exchange will tell you what you are dealing with structurally.
Can a surveyor inspect the roof timbers if foam is present?
No. Foam bonds directly to the timbers and coverings, making it impossible for the survey to assess the state of the underlying structure without removal. This is the core reason lenders are reluctant to proceed and why a specialist report is almost always recommended.
What is the difference between open-cell and closed-cell foam?
Open-cell foam is softer, semi-permeable and easier to remove. Closed-cell foam is hard, dense and impermeable, bonds more aggressively to surfaces and is significantly more expensive and difficult to remove. Closed-cell foam causes more serious ventilation problems and carries a greater risk of damaging the underlying structure during removal.
Can the seller arrange foam removal before completion?
Yes, and this is sometimes the most practical route where the seller wants to achieve a sale and the buyer is unwilling to take on the risk. Any foam removal should be carried out by a certified specialist and completed with a certificate that the buyer and their lender can rely on.
How long does foam removal take?
For an average-sized loft, removal typically takes two to five days depending on the type of foam and the complexity of the underlying structure. Additional time should be allowed if remedial repairs to timbers or roof coverings are needed once the foam has been removed.
Is foam always a problem, or can it be acceptable to a lender?
It depends on the lender, the type of foam, the availability of installation certification and the findings of any specialist assessment. Open-cell foam with full documentation and no evidence of defects is more likely to be acceptable than closed-cell foam with no paperwork. A mortgage broker will know which lenders are currently taking a more flexible approach.