Cavity wall insulation, mortgages and surveys
Unlike spray foam in lofts, ordinary cavity wall insulation is common and is not automatically a lending problem. Where it holds up a sale or remortgage, it is usually because a surveyor has linked it to damp, mould or uncertainty about the condition of the fill – not because cavity insulation exists.
Typical survey comments
- Dampness or staining on external walls, with further investigation recommended
- Possible cavity bridging or saturated insulation
- A request for a specialist damp or insulation report before exchange
RICS guidance on damp stresses finding the real moisture source and being wary of over-simple diagnoses (RICS).
If you're selling
- Find any installation and guarantee paperwork early (CIGA cover can transfer to later owners) (CIGA).
- Commission a clear specialist report if the buyer's survey is vague – photographs of the cavity help.
- If extraction is recommended and covered by guarantee, start that process promptly; complex CIGA cases can take many working days (CIGA).
- Budget privately only if there is no valid guarantee route.
If you're buying
- Ask the seller for guarantee documents and any previous reports
- Don't assume every damp patch means the fill must come out
- Get your own impartial survey before renegotiating price or walking away
Spray foam is different. If the same survey also flagged spray foam in the loft, that has its own lending issues – see spray foam and mortgages on our sister site.
Independent damp advice
When the report only says "damp – further investigation", start with cause, not cure: independent damp surveys in East London.