Most cavity wall insulation fitted under a recognised UK scheme carries a 25-year guarantee, usually registered with CIGA. Start by checking your paperwork and the CIGA postcode database. If records are missing or you’re seeing damp or cold spots, book a borescope or thermal survey before anyone talks about extraction. Only once a fault is confirmed should you approach the installer, then the guarantee provider.

TL;DR:

Guarantee records may be missing or separated from paperwork, so it is important to check the CIGA guarantee checker and historical documents thoroughly.

Signs of cavity wall insulation issues include damp patches, mould, cold spots, discolored plaster, blocked weep holes, and mortar bridging, but only surveys can confirm faults.

Borescope surveys provide direct visual evidence at costs of £80 to £150, while thermal imaging scans surface temperature differences for £150 to £300, with full surveys combining both methods.

Never pay for insulation extraction before independent verification, as premature removal can void guarantees and eliminate cost recovery options.

For accurate inspection, hire qualified surveyors working to established standards, and ensure a detailed report supports claims or sale disclosures.

How to check whether your property has a cavity wall insulation guarantee
What signs suggest your cavity wall insulation needs inspecting?
What do borescope, thermal imaging and condition surveys actually show?
How do you arrange an independent inspection and what should the report include?
How does a CIGA claim work, and what if the guarantee’s gone?
What does a CWI guarantee mean for buying or selling a house?
How does OSCAR Onsite approach cavity wall guarantee inspection?
What’s the fastest, safest route to sorting this out?
Book a cavity wall guarantee inspection with OSCAR Onsite
Where to check the official record and get further guidance
Sources

How to check whether your property has a cavity wall insulation guarantee

The quickest route is the CIGA guarantee checker, which searches by postcode and tells you whether a guarantee exists for your address. Because guarantee records contain sensitive installation details, CIGA typically asks for proof of ownership before releasing information, usually two forms of identification confirming you’re the current owner.

If the online search draws a blank, don’t assume there’s no cover. Older paperwork often gets separated from a property during a sale.

Check your property information pack, deeds, or the solicitor’s file from when you bought the house.
Ask the previous owner or their estate agent if they kept installation certificates.
If the work was funded through ECO or an earlier Green Deal scheme, contact your energy supplier or check Ofgem’s guidance on cavity wall insulation complaints, which lists the correct escalation route for funded installs.
If there’s genuinely no trace of a guarantee anywhere, you still have three options: contact the original installer directly, commission an independent condition survey, or investigate indemnity insurance if you’re mid sale and need cover in place quickly.

Not every cavity was suitable for filling in the first place. Cavities narrower than 50mm, or walls with bridging and blocked cavities, can fall outside guarantee eligibility altogether according to industry suitability guidance, which is worth knowing before you assume a fault is covered.

What signs suggest your cavity wall insulation needs inspecting?

You can’t diagnose failed cavity wall insulation just by looking at a damp patch. But certain patterns are common enough to justify booking a proper survey rather than waiting it out.

Internal damp patches on external walls, particularly ones that appeared or worsened after insulation was installed.
New or recurring mould, especially in corners and around window reveals on outside walls.
Persistent cold spots that feel noticeably colder than the rest of the wall, even with heating on.
Discoloured plaster or wallpaper that wasn’t there before the cavity was filled.
Blocked weep holes at the base of the wall, which stop moisture draining as designed.
Mortar bridging across the cavity, visible as a continuous smear of mortar between the two wall leaves.

None of these prove insulation has failed. They’re indicators that warrant evidence, not a diagnosis in themselves. A borescope or thermal survey is what actually tells you whether there’s a moisture or fill problem inside the cavity.

One more thing worth flagging: if you receive an unsolicited call about “checking your cavity wall insulation for a claim,” treat it with caution. CIGA confirms that genuine inspections are prearranged and inspectors carry identification — never let someone in on the strength of a phone call alone.

What do borescope, thermal imaging and condition surveys actually show?

Each inspection method answers a different question, and picking the wrong one wastes money.

A borescope survey involves drilling a small hole and feeding a camera directly into the cavity. It’s the only method that gives you a direct visual of the insulation itself, showing fill levels, moisture staining, debris, and wall tie condition. Costs typically run £80 to £150, and because it’s a direct view rather than an inference, it’s often the most cost-effective first diagnostic step when you need a definite answer.

Thermal imaging reads surface temperature differences across the wall and can flag areas where insulation appears missing or has settled. Typical cost is £150 to £300. It’s non-invasive and useful for scanning a whole elevation quickly, but it doesn’t see inside the cavity. It picks up a thermal signature at the surface, which is an indicator, not proof of what’s happening inside the wall. That’s why thermal imaging works best paired with a borescope for confirmation rather than used alone.

Borescope: direct view, small hole, £80 to £150, confirms fill and moisture condition.
Thermal imaging: non-invasive, whole-wall scan, £150 to £300, flags likely problem zones.
Full condition survey: combines both methods with moisture mapping and a written remediation recommendation, at higher cost but with the fullest evidence base.

A full condition survey is the option to choose if you expect to need documented evidence for a guarantee claim or a house sale, because it produces a report rather than just a reading.

How do you arrange an independent inspection and what should the report include?

Book through an independent surveyor or an accredited inspection firm rather than the original installer alone, since the installer has an obvious interest in the outcome. Ask specifically about NVQ Level 2 qualifications in CWI surveying and whether the inspector works to PAS 2030:2023 and BS 8104, the standards that govern installation quality and moisture resistance assessment for masonry walls.

Gather what you have first: the property address, installation date if known, any CIGA paperwork, and photos of the symptoms you’ve noticed.
On the day, expect borescope holes drilled at agreed points, thermal capture where relevant, and moisture readings taken across affected walls.
You should receive a written report with images, moisture data, and a clear recommendation, not a verbal opinion on the doorstep.
A credible report sets out repair options, states whether a CIGA claim looks appropriate, and provides an evidence pack you can submit alongside a guarantee complaint.

Pro Tip: Take your own dated photographs of any damp or staining before the inspector arrives. If a dispute drags on, having your own timeline strengthens the evidence pack alongside the surveyor’s findings.

How does a CIGA claim work, and what if the guarantee’s gone?

Before raising anything, check three things: the guarantee is registered, you’re within the 25-year period, and the insulation hasn’t been materially altered since installation (extended, part-removed, or built over).

Government guidance sets out the escalation order clearly: contact the installer first, then the guarantee provider, then Trading Standards or Ofgem if you’re still stuck. Raising a concern with CIGA typically triggers a CIGA-arranged independent inspection, and outcomes can range from no fault found to funded remediation.

CIGA claims have limits: pre-existing structural defects, cavities excluded at installation, and financial caps on remediation can all restrict what’s covered.
Extraction isn’t an automatic outcome of a successful claim. It depends on what the independent inspection actually finds.
If the installer has ceased trading and there’s no CIGA record, Energy Saving Trust recommends commissioning an independent assessment from a RICS surveyor or a qualified inspector as the next practical step.
For ECO or Green Deal funded installs, Ofgem’s complaint route sits alongside the standard CIGA process and is worth checking in parallel.

What does a CWI guarantee mean for buying or selling a house?

Sellers completing a TA6 form must disclose known cavity wall insulation installations and any defects they’re aware of, along with guarantee paperwork where it exists. A current, verifiable guarantee tends to reassure both the buyer and their solicitor considerably faster than a vague assurance that “it’s fine.”

If a survey flags a possible CWI issue during a purchase, buyers can reasonably ask for further testing, or remediation, before completion.
Sellers who suspect a problem, or simply can’t locate paperwork, are better off commissioning a pre-marketing inspection than waiting for a buyer’s surveyor to raise it first.
Keep any inspection reports, CIGA correspondence, and installation certificates together and ready to hand over. It’s the single fastest way to stop a query becoming a delay.

How does OSCAR Onsite approach cavity wall guarantee inspection?

OSCAR Onsite’s inspection work is built on the principle that no extraction recommendation should come before independent verification. Surveyors work to the NVQ Level 2 standards OSCAR Onsite authored for CWI surveying and inspection, alongside PAS 2030:2023 and BS 8104 awareness, and every condition survey produces a report designed to stand up to scrutiny from a guarantee provider or a conveyancing solicitor.

A rigorous inspection report combines borescope stills, moisture mapping across affected elevations, and a clear written recommendation, not a verbal opinion. That evidence pack is what a homeowner actually needs to support a CIGA claim or answer a buyer’s query with confidence.

Independent verification exists to protect homeowners from unnecessary, irreversible work. Extraction that happens before cause and condition has been established properly can forfeit the chance to recover costs under a guarantee altogether.

What’s the fastest, safest route to sorting this out?

If you’re not sure where you stand, the order of operations is simple: find your paperwork, check CIGA, look for the visible signs covered above, and book a borescope or thermal survey if anything’s uncertain. Only once that evidence exists should you contact the installer, and then CIGA if the problem isn’t resolved.

One warning worth repeating: never pay for extraction before independent verification. It’s the single most common mistake seen in practice, and it often closes off any route to recovering costs under a valid guarantee.

If you need further help beyond an inspection, RICS, Trading Standards, and Citizens Advice are all reasonable points of contact for consumer disputes that stall.

— Alan

Book a cavity wall guarantee inspection with OSCAR Onsite

Unlike a general builder’s opinion or a claims management call centre, OSCAR Onsite’s inspections are evidence-led from the start, borescope stills, moisture mapping, and a written recommendation, not a guess based on what a damp patch looks like. That distinction matters when you’re trying to satisfy a guarantee provider or a nervous buyer’s solicitor.

Every survey is carried out to the standards OSCAR Onsite helped establish nationally, including the NVQ Level 2 frameworks for CWI surveying and extraction, with PAS 2030:2023 and BS 8104 awareness built into the process. If symptoms have already appeared, or you simply can’t locate your paperwork, a CWI condition inspection survey produces the evidence pack you’ll need for a CIGA claim or a conveyancing query. Unsure whether your situation warrants a full survey yet? Start with the cavity wall insulation risk check to establish whether further testing is worth commissioning.

Where to check the official record and get further guidance

Where to check the official record and get further guidance — overview diagram

For a direct check of your own guarantee, use the CIGA guarantee checker rather than relying on memory or estate agent paperwork. GOV.UK’s consumer guide sets out the official escalation order if a claim stalls, while Ofgem’s guidance covers ECO-funded installs specifically. Energy Saving Trust offers broader consumer advice if your installer has ceased trading, and OSCAR Onsite’s industry references and standards page lists the technical standards inspectors work to.

25 Year Guarantee Checks for UK Buyers: Evidence Led Cavity Inspection

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