Cavity wall insulation and your mortgage
A mortgage valuation note about the cavity insulation does not mean the sale is off. It usually means the lender wants more information: proof of a guarantee, a specialist’s report on the condition of the fill, or in some cases the work done before it lends in full.
A report costs £50 to £300; extraction, if needed, from £900
What the lender is usually asking for
- The guarantee certificate. Often enough on its own if the valuer saw no sign of damp. Ask the seller for it now.
- A specialist’s report. A borescope survey with photographs, saying whether the fill is dry and sound.
- Remedial work, or a retention. Where damp is visible, the lender may hold back part of the loan until extraction is done, or want it done first.
- A wall tie report. If the valuer saw the horizontal crack pattern that suggests corroding ties.
What each answer costs
| Item | What it covers | Guide price |
|---|---|---|
| Guarantee check | Seller’s certificate or a check with the guarantee provider | Free |
| Specialist report | Borescope survey written up for the lender | £50 to £300 |
| Wall tie report | If the lender asks for one | £250 to £450 |
| Extraction, semi-detached | If the report says the fill has failed | £1,600 to £2,400 |
Guide prices before VAT from published UK price guides, read November 2026. Work out your own house.
Up against a completion date? Tell us the postcode and we will look for a specialist who can survey quickly.
Get a survey before completionBuying, selling and the cavity fill
If you are buying
Read exactly what the valuation says. “Cavity wall insulation noted” with a request for a guarantee is very different from “damp readings to the inner face of external walls, possibly related to cavity insulation”. Pass the wording to the seller through the agents and ask for the guarantee certificate, any correspondence with the installer and any past survey.
If the lender wants a report, it should be a specialist inspection of the cavity itself, not a general opinion. Ask the surveyor to state the fill type, its condition on each elevation, whether there is bridging, and the state of the ties, with photographs. That is what an underwriter can act on.
If extraction is needed, it can be done before completion (the seller pays or reduces the price), or after (the lender may hold back a retention until it is done). Your conveyancer will advise; lenders’ standing instructions to conveyancers are set out in the UK Finance Mortgage Lenders’ Handbook.
If you are selling
- Find the guarantee now, before a buyer’s valuer asks. CIGA can confirm whether one was issued for your address.
- If you suspect the fill has failed, a survey before marketing puts you in control of the price conversation.
- If you have had extraction done, keep the specialist’s completion report and any new guarantee with the deeds.
Remortgaging
The same applies, without the time pressure of a chain. A desktop or drive-by valuation rarely picks up cavity fill; a full inspection may.
Where our information comes from
- UK Finance: Mortgage Lenders’ Handbook
- GOV.UK (BEIS): Cavity wall insulation, consumer guide to issues arising on installation (October 2019)
- Welsh Government: A consumer guide to issues arising from cavity wall insulation installations in Welsh properties (2021)
- CIGA (Cavity Insulation Guarantee Agency): guarantees and homeowner concerns
Prices are typical ranges from published UK contractor and trade price guides, read November 2026, before VAT. Guidance is summarised in our own words; it is general information, not advice on your particular house.
How the job gets done
The quickest route from a valuation note to a satisfied lender.
Read the wording
Is the lender asking for a certificate, a report or the work itself?
Find the guarantee
From the seller, the installer or CIGA.
Specialist report
Borescope survey, photographs, a clear conclusion.
Work or retention
Extraction before completion, or a retention until it is done.
Questions homeowners ask
Can I get a mortgage on a house with cavity wall insulation?
What is a mortgage retention?
Who pays for the report?
How quickly can a report be done?
Does failed cavity insulation lower the value?
Keep reading
- Cavity survey
What a report should contain.
- CIGA guarantee claims
Find out if the fill is guaranteed.
- Wall tie replacement
When the valuer also mentions cracking.
Tell us what the walls are doing
Three short steps. Your postcode, the house and what you are seeing are enough to start. The specialist confirms the detail with a borescope survey before any price is fixed.
Costs you nothing. We hold on to what you send until you have agreed to the extraction specialist we suggest.
Got it. What happens now:
- We find an independent extraction specialist working near you who deals with walls like yours, and email or ring to tell you who they are.
- Your details stay here until you agree to that firm.
- Once you agree, they book a camera survey of the cavity and send a written price. We will not add you to any mailing list or ring you to sell anything.