Window Guarantee Without FENSA: What to Do

A window guarantee is reassuring to have. It tells you that the manufacturer or installer stands behind the product and will address defects within a defined period — often 10 to 20 years. But a guarantee is a commercial document. It says nothing about whether the windows were installed in compliance with the Building Regulations. During conveyancing, it is the regulatory compliance certificate that matters to the buyer's solicitor and their mortgage lender.

If your replacement windows do not have FENSA registration or an equivalent certificate, you have a compliance gap that will need to be addressed before your sale can progress. This guide explains why the gap exists, what it means in practice, and how to resolve it.

The difference between a window guarantee and a FENSA certificate

Understanding why these two documents serve different purposes is essential before you can make an informed decision about what to do.

A quality window guarantee from a reputable manufacturer is a desirable feature of the property. Buyers will be pleased to receive it. But it has no bearing on whether the installation was notified to the local authority or certified as meeting Part L of the Building Regulations. An installer can issue a 20-year guarantee on windows they installed without any FENSA registration, and the guarantee remains valid. The absence of FENSA registration is an entirely separate issue.

Why the Building Regulations apply to replacement windows

Before 1 April 2002, replacing windows in a residential property was not notifiable work under the Building Regulations. Homeowners and installers could carry out replacements without informing the local authority.

From 1 April 2002, that changed. The Building Regulations 2000 were amended to make replacement windows and external doors notifiable work under Part L, which governs energy efficiency and the conservation of fuel and power. The purpose was to ensure that new window installations met minimum thermal performance standards, reducing heat loss in existing housing stock.

To avoid requiring every homeowner to make a formal building regulations application, the government authorised competent person schemes — including FENSA — to allow registered installers to self-certify compliance and notify the local authority on the homeowner's behalf. An installer who is not registered with FENSA or CERTASS must instead apply for building regulations approval through the local authority before carrying out the work.

In practice, many installations during the early years of the scheme were carried out by small traders who were not FENSA-registered and did not obtain local authority sign-off. This is why missing FENSA certificates are such a common issue for sellers today.

How this issue surfaces during conveyancing

The missing FENSA certificate will almost always come to light during the conveyancing process. There are two main ways it emerges:

The TA6 Property Information Form

You will be asked to complete the TA6 Property Information Form, which includes a section on alterations and installations at the property. Section 6 asks specifically whether any building work or alterations have been carried out and whether the relevant consents and certificates were obtained. You must disclose that windows were replaced and whether you hold a FENSA, CERTASS, or building control certificate. If you declare that the certificates are absent, the buyer's solicitor will raise a pre-contract enquiry requiring the issue to be resolved before exchange.

The local authority search

The buyer's solicitor will order a local authority search as part of the standard conveyancing process. This search reveals building control applications and FENSA or CERTASS notifications lodged for the property. If replacement windows are visible at the property but no corresponding record appears, the discrepancy will be flagged. Even if you do not mention the windows on the TA6 form, the search may still surface the issue.

In either case, the matter needs to be resolved before exchange of contracts. The buyer's solicitor cannot advise their client to proceed — and the mortgage lender cannot release funds — with an outstanding building regulations compliance issue.

Checking whether your windows were registered

Before assuming you have a problem, it is worth checking whether the installation was registered and the certificate simply lost. Installers are required to notify FENSA within 10 working days of completing a job, and FENSA issues the certificate to the homeowner within four to six weeks.

To check FENSA registration:

1. Visit fensa.org.uk and use the online certificate checker.
2. Enter your property's postcode and select your address from the results.
3. Review the results for any registered installations, including the date and the installer's name.

If an installation is registered, you can request a duplicate certificate from FENSA for a small fee (typically £5 to £10). This resolves the issue entirely.

If nothing appears, also check the CERTASS database at certass.co.uk, as the installer may have used that scheme instead. You can also contact the installation company directly — they may hold records of the job and can help you trace any registration.

If neither database shows a record and the installer either cannot be contacted or confirms they were not registered, you have a genuine compliance gap and need to choose between the two resolution options below.

Option 1: Indemnity insurance

Indemnity insurance is the most commonly used solution for older window installations without FENSA registration. It is a one-off insurance policy that protects the buyer and their mortgage lender against the financial consequences of the local authority taking enforcement action over the non-compliant installation.

The legal basis for indemnity insurance as a solution rests on Section 36 of the Building Act 1984. This section gives the local authority the power to serve an enforcement notice requiring work to be altered or removed if it contravenes the Building Regulations — but only within 12 months of the work being completed. After this period, the enforcement right under Section 36 expires. This means that for windows installed more than a year ago, the practical risk of enforcement action is very low, and indemnity insurance is an affordable and widely accepted way to manage the residual risk.

What an indemnity policy covers

• The cost of complying with any enforcement notice served by the local authority (including the cost of altering or replacing the windows)
• Legal fees incurred as a result of enforcement proceedings
• Any diminution in the property's value resulting from enforcement action

The policy is issued as a one-off premium with no annual renewals. It passes automatically to future owners of the property and remains in force indefinitely. For window installations, the premium is typically £30 to £150, depending on the property value, the number of windows covered, and the insurer.

The critical condition: do not contact the local authority

Indemnity insurance has one non-negotiable condition. You must not have contacted or notified the local authority about the windows before the policy is arranged. If building control has been approached — for example, to enquire about regularisation, to ask about the installation records, or to report a concern — most insurers will refuse to issue a policy, or any existing policy will be voided.

This condition exists because insurers price policies on the basis that the local authority is unaware of the non-compliant installation. If the authority has been notified, the enforcement risk increases significantly.

The implication for sellers is clear: decide between indemnity insurance and regularisation before taking any action. Do not contact the local authority and then attempt to obtain indemnity insurance. Speak to your solicitor first.

When indemnity insurance is the right choice

• The windows were installed more than 12 months ago
• You need to resolve the issue quickly (indemnity can be arranged within one to five working days)
• The windows are in good condition with no visible defects or signs of non-compliance
• You have not contacted the local authority about the installation
• The buyer's mortgage lender is willing to accept an indemnity policy (most mainstream lenders are, for older window installations)

Option 2: Regularisation

Regularisation is the formal route for obtaining retrospective building regulations approval. It is authorised by regulation 18 of the Building Regulations 2010 and involves applying to your local authority building control department for a certificate confirming that the windows comply with Part L.

Unlike indemnity insurance, regularisation provides positive proof that the windows meet the regulatory standard. It is the stronger solution and is universally accepted by mortgage lenders and buyer solicitors. The regularisation process for building regulations sign-off follows the same general steps regardless of the type of work.

How regularisation works for windows

1. Apply to your local authority building control department. Explain that replacement windows were installed without FENSA registration or building control sign-off and that you are seeking retrospective approval. Provide the approximate date of installation and any documentation you have.
2. A surveyor inspects the windows. The building control surveyor will assess whether the windows meet the Part L thermal performance requirements in force at the time of installation. For windows, the inspection is usually straightforward — no structural opening up is required.
3. Certificate issued (or remedial work specified). If the windows meet the required standard, a regularisation certificate is issued. If they do not — for example, if they are single glazed or have very poor thermal performance — the local authority may specify that the windows need to be upgraded or replaced before a certificate can be issued.

For window regularisation, the fee is typically £200 to £400, and the process takes two to four weeks. This is shorter than regularisation for structural work, which can take considerably longer.

When regularisation is the right choice

• The windows were installed within the last 12 months (the Section 36 enforcement window is still open, making indemnity insurance less suitable)
• You want to provide the buyer with the strongest possible documentation and peace of mind
• You have time before listing the property to complete the process
• The buyer's mortgage lender specifically requires a regularisation certificate rather than indemnity insurance

Comparing the two options

What happens to the window guarantee during this process?

Resolving the FENSA compliance issue does not affect the window guarantee. The guarantee remains valid independently of whether you arrange indemnity insurance or obtain a regularisation certificate. You should pass the original guarantee documentation to the buyer as part of the property handover.

If the guarantee is from a company that has since gone out of business, check whether it was backed by a third-party insurance scheme such as the Glass and Glazing Federation's deposit protection scheme or an independent warranty provider. Some manufacturer warranties are underwritten independently and remain valid even after the installer or manufacturer ceases trading. If so, you should be able to obtain a certificate of insurance from the warranty provider confirming the guarantee is still in force.

Bear in mind that the buyer's solicitor may ask for both the compliance certificate (FENSA equivalent) and the guarantee. Having both documents ready before you list is the cleanest position and avoids delays once solicitors are instructed.

What if some windows are registered and some are not?

It is common for a property to have a mixture of registered and unregistered window installations, particularly where windows were replaced at different times or by different contractors. You need documentation for each installation separately.

Search the FENSA database for each set of windows and make a note of which are registered and which are not. For unregistered installations, you will need to decide whether to pursue indemnity insurance or regularisation for each one. In many cases, your solicitor will arrange a single indemnity insurance policy that covers all unregistered installations at the property, which simplifies the process and reduces costs compared with arranging separate policies.

Including window documentation in your property certificate pack

The property certificate pack is the collection of compliance documents you assemble before listing your home. FENSA certificates, CERTASS certificates, or regularisation certificates for windows should be included alongside other compliance documents such as the Gas Safe certificate, electrical installation certificates, and any building control completion certificates for structural work.

If you are relying on indemnity insurance for unregistered windows, the policy document should also be included in the pack and passed to your solicitor so they can provide it to the buyer's solicitor as part of the pre-contract documentation.

Assembling these documents before you find a buyer gives you time to identify and resolve gaps without pressure. Discovering a missing FENSA certificate after you have accepted an offer can create unnecessary delays and, in some cases, may give a buyer an opportunity to renegotiate the price.

The cost of doing nothing

Some sellers are tempted to hope the issue will not be raised during conveyancing. This is an unreliable strategy for several reasons:

• The TA6 form requires you to disclose alterations. Failing to disclose a known issue can constitute misrepresentation and expose you to a claim for compensation after completion.
• The local authority search may reveal a building control record that flags the issue regardless of what you disclose.
• A buyer's surveyor may note that replacement windows appear to be of a certain age and prompt the solicitor to ask for documentation.
• Lenders following the UK Finance Mortgage Lenders' Handbook will require confirmation that window replacements have proper sign-off. Without it, the buyer may not be able to complete their mortgage.

Dealing with the issue proactively — before marketing the property — is almost always faster and cheaper than addressing it under pressure once a buyer is in place. The costs of selling a house can mount quickly when conveyancing delays lead to abortive legal fees or buyers withdrawing from transactions.

Practical steps to take now

1. Check the FENSA and CERTASS databases for your property address. This takes a few minutes and may reveal that the installation is already registered.
2. Contact the installer if the database shows no record. Ask whether they registered the job and, if so, under which scheme. If they can confirm registration, they may be able to arrange a duplicate certificate.
3. Decide your approach before contacting anyone else. If the installation is more than 12 months old, indemnity insurance is typically the faster and more cost-effective route. If it is recent, regularisation is more appropriate. Speak to your solicitor to confirm which option suits your specific circumstances.
4. Do not contact the local authority until you have decided your approach. If you want indemnity insurance, approaching building control before the policy is in place will void your options.
5. Gather all window documentation, including the guarantee, any installation invoices, and whatever compliance documentation you have or obtain. Include everything in your property certificate pack.
6. Disclose accurately on the TA6 form. Once you have resolved the compliance gap, you can confirm on the form that indemnity insurance is in place or that a regularisation certificate has been issued.

Sources

• FENSA (Fenestration Self-Assessment Scheme) — fensa.org.uk
• CERTASS (Competent Person Scheme for windows and doors) — certass.co.uk
• Building Regulations 2010, Part L (Conservation of fuel and power) — legislation.gov.uk
• Building Regulations 2010, regulation 18 (Regularisation) — legislation.gov.uk
• Building Act 1984, Section 36 (Enforcement of building regulations) — legislation.gov.uk
• GOV.UK — Competent person schemes: current schemes and types of work
• UK Finance Mortgage Lenders' Handbook — ukfinance.org.uk
• Law Society — TA6 Property Information Form, 4th edition
• Local Authority Building Control (LABC) — labc.co.uk

Frequently asked questions