This guide covers the issues that come up most often and the evidence that satisfies a lender.
Spray foam insulation in the loft
Spray foam in a roof space has become a common reason for a mortgage to be declined or made conditional, because some lenders worry it hides or traps moisture against the timbers and complicates a future roof inspection. The route to resolution is usually an independent survey of the roof and the foam, and where needed professional removal, with documentation a lender can see. Frame removal as a survey-led decision, not an automatic job.
Damp and timber
Rising or penetrating damp, and associated timber decay, are flagged on surveys regularly. The accredited route is a damp and timber survey by a Property Care Association member, which diagnoses the actual cause (which is often a building defect such as a failed gutter rather than rising damp) before any treatment. A PCA-backed report and any guaranteed remedial work is the evidence a buyer or lender wants.
Japanese knotweed
Japanese knotweed can affect mortgageability because of its potential to damage structures and spread to neighbouring land. RICS guidance for residential property sets out how it should be assessed and managed. The practical resolution is a survey, a professional management plan, and often an insurance-backed guarantee, which together usually satisfy a lender rather than the presence of knotweed automatically killing a sale.
Septic tanks and the general binding rules
A property on a septic tank must comply with the Environment Agency general binding rules (gov.uk). A tank that discharges to a watercourse, or that does not meet the rules, can be a condition of sale. The fix is usually a drainage survey, then an upgrade to a treatment plant or a compliant soakaway, documented for the buyer.
EWS1 and external wall systems
For flats and some buildings with cladding or balconies, a lender may require an EWS1 form before lending. The EWS1 process is run through RICS guidance and is completed by a suitably qualified professional. Where one is needed and missing, obtaining a valid EWS1 is the unlock, and it is a building-level rather than a flat-level document.
Common questions
Why do lenders worry about spray foam in a loft?
Some lenders are concerned that spray foam can trap moisture against roof timbers and make a future roof inspection harder, so they decline or make the mortgage conditional. An independent roof and foam survey, and professional removal with documentation where needed, is the usual route to resolve it.
Does Japanese knotweed make a house unsellable?
Usually no. RICS guidance sets out how knotweed is assessed and managed for residential property. A survey, a professional management plan and often an insurance-backed guarantee typically satisfy a lender, rather than the plant automatically blocking a sale.
What is an EWS1 form and when do I need one?
EWS1 is an external wall system assessment that a lender may require before lending on flats or buildings with cladding or balconies. It is completed under RICS guidance by a qualified professional and is a building-level document, so obtaining a valid one is the unlock when it is missing.
Do I have to fix a damp survey finding before selling?
Not always, but it helps. A Property Care Association damp and timber survey diagnoses the real cause, which is often a building defect rather than rising damp. A PCA-backed report and any guaranteed remedial work is the evidence a buyer or lender looks for.
Sources
Where to go next
More home improvement guides
VettedHome is an independent home information site, not a lender or installer.
Editor, VettedHome
Adam leads VettedHome's editorial coverage of UK home services. He is the founder and managing director of Muswell Rose, the commercial strategy and modern systems business behind a portfolio of UK information sites, and he researches and writes the plain-English guides that help homeowners choose between installers and trades, drawing on the standards set by the relevant bodies for each job, such as Gas Safe Register, NICEIC, MCS, TrustMark and the Property Care Association. He is clear about what to check before any work starts.
Last updated: