If you are buying or selling a property with spray foam insulation in the loft, there is a strong chance that a RICS-qualified surveyor will flag it. For many homeowners, this comes as a surprise — the spray foam may have been there for years, the loft may feel warmer, and no problems may be obviously visible. So why are surveyors so concerned?

Understanding what a RICS surveyor is actually looking for when they encounter spray foam helps demystify what can feel like an overly cautious or obstructive response. Their concerns are specific, technically grounded, and — for the most part — entirely reasonable given the limitations spray foam creates for a proper structural assessment.

The Surveyor’s Responsibility

A RICS surveyor carrying out a HomeBuyer Report or Building Survey has a professional duty to assess the condition of the property and report on any defects, risks, or matters requiring further investigation. This duty is owed to their client — typically the buyer or the mortgage lender — not to the seller, and not to any insulation contractor who may have a view on the quality of their own work.

When the surveyor encounters spray foam, they are not obliged to accept the seller’s assurances that it is fine, or to rely on a guarantee document from the original installer. They are required to form their own professional view of the risks it presents and to communicate those risks clearly in their report.

What They Look for in the Loft

Type of Foam

The first question is what type of foam has been applied. Open-cell spray foam is a softer, more flexible material that allows moisture to pass through. Closed-cell spray foam is rigid, impermeable, and significantly harder to remove cleanly. The distinction matters because closed-cell foam carries higher risk in terms of moisture trapping and the difficulty of post-removal timber assessment. Surveyors note the type where it can be identified, and where it cannot be confirmed visually, they will typically assume a worse-case position in their report.

Application Location and Coverage

Spray foam applied to the underside of roof tiles or slates — directly to the inner face of the roof covering — is treated with greater concern than foam applied elsewhere. This is the most common retrospective application and the one most likely to cause problems with moisture, ventilation, and tile integrity. Surveyors will check the extent of coverage and whether critical areas such as eaves, ridge, and valley junctions have been sealed.

Visible Timber Condition

Where timber is accessible — at the eaves, at the ridge, at wall plate level — surveyors will use a moisture meter and carry out a visual inspection. They are looking for discolouration, softness, cracking, or any other evidence of moisture-related decay. Elevated readings from accessible timbers raise serious concern about what may be happening in the concealed sections beneath the foam.

The Concealment Problem

This is the central issue that every RICS surveyor will address: spray foam makes it impossible to inspect the rafters and structural timbers properly. A Building Survey report is explicit about this limitation. The surveyor will note that they cannot confirm the condition of the concealed timbers and will recommend specialist investigation — which in practice often means removal of the foam to carry out a full structural inspection.

Ventilation Assessment

A well-functioning cold loft space requires ventilation — air entering at the eaves and exiting at the ridge or through tile vents. This prevents condensation and keeps the timber dry. Surveyors check whether ventilation paths have been blocked by the foam application, whether soffit vents are obstructed, and whether there is any evidence of condensation on exposed surfaces. A loft that is clearly sealed and showing signs of moisture is a significant concern in any survey report.

The Impact on Mortgage Lending

RICS surveyors carry out valuations on behalf of mortgage lenders, and their findings directly affect lenders’ decisions. When spray foam is flagged as a risk in a valuation report, lenders may apply one of several responses:

• A retention — where a proportion of the mortgage offer is withheld pending resolution of the spray foam issue
• A condition — requiring an independent specialist report before funds are released
• A reduced valuation — where the lender values the property below the agreed purchase price, affecting the loan-to-value ratio
• Refusal to lend — in cases where the surveyor’s concerns are severe or the lender’s policy on spray foam is restrictive

Not all lenders treat spray foam identically. Some will accept an independent inspection report confirming the foam is in sound condition; others have a blanket policy of requiring removal before they will proceed. If you are selling a property with spray foam, understanding your buyer’s lender’s position early in the process can save significant time and cost.

What You Can Do to Address Surveyor Concerns

If a surveyor has flagged spray foam in a report, or if you are preparing to sell or remortgage and want to understand your position in advance, there are a number of proactive steps worth taking. An independent specialist assessment — carried out before a transaction is under way — gives you documented evidence of the foam’s current condition and the state of accessible timbers. This can form part of the sales pack provided to buyers, reduce the likelihood of surprises during the buyer’s survey, and allow you to manage any issues on your own timeline rather than under transaction pressure.

Key Takeaways

• RICS surveyors check foam type, coverage, timber condition, and loft ventilation
• The core issue is that spray foam makes proper structural inspection of roof timbers impossible
• Surveyors are professionally obliged to flag this limitation — it is not a matter of personal opinion
• Lender responses to a spray foam flag can range from a retention to a refusal to lend
• Proactive independent assessment before a sale or remortgage reduces the risk of transaction delays