Cavity Wall Insulation Guarantee

Cavity wall insulation is one of the most common energy efficiency improvements in UK homes. An estimated 16 million properties in Great Britain have cavity walls, and millions of them have been insulated — many under government-funded schemes dating back to the 1990s. If your property has had cavity wall insulation installed, it should have come with a guarantee, and that guarantee is a document your buyer's solicitor will almost certainly ask about during conveyancing.

This guide explains what CWI guarantees cover, how to find out if yours is registered, what to do if the insulation has failed, and how to handle the disclosure requirements on the TA6 Property Information Form.

What is cavity wall insulation?

Cavity wall insulation (CWI) involves filling the gap (the “cavity”) between the inner and outer leaves of an external wall with an insulating material. The cavity was originally left empty to prevent moisture from crossing from the outer to the inner wall. CWI works by filling that void with a material that resists heat transfer while (in theory) not bridging moisture.

The most common insulation materials used in UK properties are:

• Mineral wool (rock wool or glass wool). Loose fibres blown into the cavity under pressure. This is one of the oldest and most widely used methods, and it is generally considered suitable for most cavity walls in England and Wales.
• Expanded polystyrene (EPS) beads. Small beads bonded with a water-repellent adhesive, blown into the cavity. The bonded bead system is often considered more resistant to moisture issues than loose fill in exposed or wind-driven rain zones.
• Urea formaldehyde (UF) foam. A foam injected into the cavity that sets hard. This material was widely used in the 1970s and 1980s but fell out of favour due to concerns about shrinkage, cracking, and off-gassing. Properties with UF foam insulation may attract additional scrutiny from buyers and lenders.

Whether a property is suitable for CWI depends on the width and condition of the cavity, the exposure zone (how much wind-driven rain the property receives), and the age and construction type of the building. Installers are required to assess suitability before installation under British Standard BS 8208 and the relevant CIGA code of practice.

The CIGA guarantee scheme

The Cavity Insulation Guarantee Agency (CIGA) is the main industry body responsible for issuing and administering guarantees on cavity wall insulation in the UK. CIGA was established in 1995 following growing concerns about the quality of CWI installations carried out under earlier government schemes.

When a CIGA-registered installer carries out cavity wall insulation, they issue a CIGA guarantee to the property owner. The guarantee is backed by a separate insurance policy held by CIGA, which means that if the installer goes out of business, the guarantee remains valid and CIGA will step in to deal with any claims. This is the same principle as an insurance-backed guarantee (IBG) found in other building work warranties.

What the CIGA guarantee covers

The CIGA guarantee covers:

• Failure of the insulation material itself (for example, if it settles, degrades, or loses its insulating properties)
• Defects in the installation that cause the insulation to perform below the specified standard
• Remediation costs, including extraction of failed insulation and re-installation if required

The CIGA guarantee does not cover:

• Pre-existing defects in the property's structure or building fabric (such as cracked render, failed pointing, or defective window seals) that existed before the insulation was installed
• Damp caused by other sources, such as rising damp, roof leaks, or plumbing failures
• Consequential losses or damage to internal decoration or contents
• Installations where the property was not assessed as suitable for CWI before the work was done

Duration and transferability

CIGA guarantees last 25 years from the date of installation and are fully transferable to new owners at no charge. This means that if you are selling a property where the insulation was installed 10 years ago, the buyer inherits 15 years of remaining coverage. No notification or registration is required at the time of transfer — the guarantee passes with the property automatically.

How to check if your guarantee is registered

The simplest way to confirm whether a CIGA guarantee exists for your property is to use the CIGA guarantee checker at ciga.co.uk. Enter your postcode and you will be able to see whether any guarantees are registered for your address.

If the property is in the database, CIGA can reissue the certificate on request, usually within a few days. This is useful if you have lost the original paperwork.

If the CIGA checker shows no record, try the following:

1. Check your conveyancing file. If the insulation was installed before you purchased the property, the guarantee should have been included in the conveyancing documents you received when you bought. Contact the solicitor who acted for you on that purchase.
2. Check your home information pack or survey. If you purchased the property before 2012, it may have come with a home information pack (HIP) that included energy efficiency certificates and any related documentation.
3. Contact the original installer. If you know who installed the insulation, contact them directly. CIGA member installers are required to register guarantees, but records from the 1990s or early 2000s may not always be on the online database.
4. Check energy company records. Much of the CWI installed in the UK was funded through energy company obligation schemes such as the Energy Efficiency Commitment (EEC), the Carbon Emissions Reduction Target (CERT), or the later ECO scheme. If you know which energy supplier funded the work, they may hold records.

When cavity wall insulation goes wrong

Not all cavity wall insulation performs as intended. In some cases, poorly assessed or poorly installed CWI has been a direct cause of significant problems in UK homes, including persistent damp, mould, structural issues, and thermal performance far below what was promised.

Signs of failed CWI

The symptoms of failed or failing cavity wall insulation can include:

• Internal damp or wet patches on external walls, particularly after periods of heavy or wind-driven rain
• Mould growth on internal walls, especially in corners, behind furniture, and on surfaces adjacent to external walls
• Cold spots on internal walls in areas where insulation may have settled or not filled the cavity evenly
• Increased heating bills despite the presence of insulation
• Condensation on windows and cold surfaces that appears to have worsened since the insulation was installed
• Visible staining, salt deposits, or bubbling paint and plaster on internal walls

If you notice any of these symptoms, it does not automatically mean the CWI has failed — some of them may have other causes, such as condensation, defective external render, or plumbing issues. However, it is worth investigating before you put the property on the market, because a buyer's surveyor will flag any signs of damp or moisture damage in their report.

For guidance on how damp-related issues affect a sale more broadly, see our guides on selling a house with mould and selling a house with rising damp.

Which property types are most at risk

CWI failure is more common in certain property types and locations. The main risk factors are:

• Exposed locations. Properties in areas with high rainfall or persistent wind-driven rain — particularly in Wales, the north of England, and coastal areas — are at greater risk. The insulation can become saturated if the outer leaf of masonry is not in perfect condition.
• Narrow cavities. Walls with a cavity narrower than 50mm are not generally considered suitable for CWI, as there is insufficient space for the insulation to fill without bridging.
• Older or defective masonry. If the outer leaf has cracked or failed mortar joints, porous brickwork, or damaged render, water can penetrate and wet the insulation. Once wet, cavity wall insulation can conduct moisture across to the inner leaf.
• Non-traditional construction. Properties built using non-standard methods — such as Airey houses, BISF (British Iron and Steel Federation) houses, or other prefabricated types — are not normally suitable for CWI and should not have had it installed. If they have, the risk of problems is high.

Making a claim under the guarantee

If you believe the cavity wall insulation has failed, you can make a claim under the CIGA guarantee. Here is what the process involves:

1. Contact CIGA directly. Report your concerns at ciga.co.uk or by telephone. Provide your property address, the approximate date of installation, and a description of the symptoms you have noticed.
2. Independent inspection. CIGA will arrange for an independent surveyor to inspect the property. The surveyor will assess whether the damp or other problems are likely to be caused by the CWI installation or by pre-existing defects outside the scope of the guarantee.
3. Outcome. If the surveyor determines the insulation has failed or was improperly installed, CIGA will fund remediation. This may involve targeted repairs, partial extraction, or complete extraction and re-installation. If the surveyor concludes the problems are not covered by the guarantee, you will need to explore alternative routes such as a specialist damp survey or legal advice.

It is worth noting that making a claim under the guarantee does not prevent you from selling the property. You can initiate a claim and notify the buyer of its progress as part of the conveyancing process. In some cases, buyers are comfortable proceeding with an active CIGA claim in place, provided there is clarity about how the issue will be resolved. This is a matter for negotiation between the parties' solicitors.

CWI and the conveyancing process

Cavity wall insulation comes up at several points during the sale of a property. Understanding where it fits into the conveyancing timeline allows you to prepare the right documentation in advance and avoid delays.

The TA6 Property Information Form

The TA6 form asks sellers to disclose alterations, improvements, and energy efficiency works carried out on the property. Section 7 covers services and energy efficiency measures and requires you to confirm whether cavity wall insulation has been installed. If it has, you will need to provide:

• The approximate date of installation
• The name of the installer (if known)
• Whether a guarantee was issued and whether it is still valid
• Whether there are any known problems, claims, or defects relating to the insulation

Answering these questions honestly is essential. Deliberately concealing known problems with cavity wall insulation — particularly if they are causing damp — can expose you to a misrepresentation claim after completion. If you are uncertain about something, include what you know and add a note explaining the uncertainty rather than leaving the question blank.

Buyer's surveyor findings

During a RICS HomeBuyer Report or Building Survey, the surveyor will look for signs of damp and moisture in external walls. If they identify evidence that may be consistent with CWI failure — such as localised damp patches on external walls, mould growth, or elevated moisture meter readings — they will typically recommend specialist investigation. This recommendation will prompt the buyer's solicitor to raise enquiries about the insulation and the guarantee.

Having the CIGA guarantee certificate ready to provide in response to such enquiries speeds up the process and demonstrates that the installation is warranted. If the surveyor has raised concerns but you have a valid guarantee and no active claim, the buyer's solicitor will usually accept this as satisfactory — though the buyer themselves may still want a specialist CWI survey for their own peace of mind.

Mortgage lender requirements

Some mortgage lenders take a cautious approach to properties with cavity wall insulation, particularly in high exposure zones or where the survey has flagged damp. In these cases, the lender may require a specialist cavity wall inspection or a satisfactory report confirming the insulation is not causing problems before releasing funds. Sellers should be aware of this possibility and factor it into their timeline, as arranging a specialist inspection takes time.

The impact on your property's Energy Performance Certificate rating may also be a factor. If the insulation has been extracted or is known to have failed, your EPC may not reflect the energy efficiency improvements it would otherwise provide.

Extraction of failed CWI

In cases where cavity wall insulation has failed and is causing damp, extraction is often the recommended solution. The process involves drilling holes in the external masonry (similar to the installation process in reverse), using industrial vacuum equipment to remove the insulation material, and then repointing the drill holes.

Costs

The cost of CWI extraction depends on the size of the property and the type of insulation material:

If the extraction is carried out under a CIGA guarantee claim, these costs are covered by the guarantee rather than falling on the seller. If there is no guarantee or the claim is not upheld, extraction costs are borne by the property owner. This is a significant expense and may affect how you negotiate with the buyer or price the property.

What to do if you suspect CWI problems before selling

If you are preparing to sell and are concerned about your cavity wall insulation, here is a practical checklist:

1. Check the CIGA database at ciga.co.uk to confirm whether a guarantee is registered for your property.
2. Inspect the internal walls for any signs of damp, cold spots, or mould growth, particularly on external walls during or after wet weather.
3. If you find signs of damp, commission a specialist CWI inspection before marketing. A certified inspector can assess whether the insulation is causing the problem and provide a written report. This puts you in control of the information rather than leaving it to be discovered in the buyer's survey.
4. If the inspection confirms a problem, contact CIGA to initiate a guarantee claim before or alongside your sale process.
5. Ensure your TA6 form answers are complete and honest, including details of the installation, the guarantee, and any known issues.
6. Review your EPC and consider whether the certificate accurately reflects the current state of the insulation. If the insulation has been extracted or is inoperable, your EPC may need updating.
7. Gather all related documents — the CIGA certificate, any correspondence with CIGA or the installer, survey or inspection reports — as part of your general property certificate pack to hand to your solicitor.

For sellers worried about the broader costs of selling a house, it is worth getting ahead of potential CWI issues early. An extraction or remediation carried out before marketing avoids the risk of a buyer using the issue to negotiate a larger discount than the actual repair cost warrants.

Non-CIGA and older guarantee schemes

Not all cavity wall insulation installed in UK properties was carried out by CIGA-registered contractors. Some older installations — particularly those from the 1980s and early 1990s — may have been covered by other guarantee schemes that have since wound up. Common examples include:

• BBA (British Board of Agrément) certificates. These are product approval certificates rather than installation guarantees, but they demonstrate that the insulation material met the required standard at the time. A BBA certificate does not provide the same level of consumer protection as a CIGA guarantee.
• Installer-issued guarantees. Some installers provided their own standalone guarantees not backed by CIGA or a separate insurer. These guarantees are only as good as the contractor who issued them and become worthless if the company has ceased trading.
• Energy company-backed warranties. Some energy companies that funded CWI installations under obligatory schemes issued their own warranty documents. Check the terms carefully, as the level of protection varies significantly.

If your property has older insulation covered by one of these schemes rather than a current CIGA guarantee, your solicitor may advise obtaining a specialist inspection to provide evidence of the current condition, particularly if the original guarantee has expired or cannot be traced.

Sources

• Cavity Insulation Guarantee Agency (CIGA) — ciga.co.uk
• British Standard BS 8208: Guide to assessment of suitability of external cavity walls for filling with thermal insulants — bsigroup.com
• Energy Saving Trust: Cavity wall insulation guidance — energysavingtrust.org.uk
• Royal Institution of Chartered Surveyors (RICS): Residential property surveys — rics.org
• British Board of Agrément (BBA) — bba.stars.com
• Law Society — TA6 Property Information Form, 5th edition, 2020
• Department for Energy Security and Net Zero: ECO scheme guidance — gov.uk

Frequently asked questions