FENSA Certificate Explained

When replacement windows or external doors are installed in England and Wales, the work must comply with Part L of the Building Regulations, which covers energy efficiency. The most common way this compliance is demonstrated is through a FENSA certificate. If you are selling your home and the certificate is missing, the buyer's solicitor will raise it as a concern — and it will need to be resolved before exchange of contracts.

This guide explains what FENSA is, how the scheme works, what to do if your certificate is missing, and how the issue is handled during the conveyancing process.

What is FENSA?

FENSA stands for the Fenestration Self-Assessment Scheme. It is a government-authorised competent person scheme that allows registered window and door installers to self-certify that their work complies with Part L of the Building Regulations 2010.

The scheme was launched on 1 April 2002 by the Glass and Glazing Federation (GGF). Before FENSA existed, every window replacement required a separate application to local authority building control. FENSA simplified this process by allowing registered installers to certify compliance themselves and notify the local authority directly.

When a FENSA-registered installer completes a window or door replacement, they notify FENSA within 10 working days. FENSA then:

• Registers the installation on their central database
• Notifies the local authority on behalf of the homeowner
• Issues a FENSA certificate to the homeowner, confirming compliance with Part L of the Building Regulations

The FENSA certificate serves as the equivalent of a building control completion certificate for the specific work covered. This means you do not need a separate sign-off from the local authority.

What does a FENSA certificate cover?

FENSA covers the replacement of existing windows and external doors in residential properties in England and Wales. The key word is “replacement” — the scheme applies when an existing window or door is removed and a new one is installed in the same opening.

FENSA does not cover:

• New windows in extensions or new-build properties (these are covered by the building control process for the extension or build itself)
• Repairs to existing windows, such as replacing a broken pane or fixing a handle
• Secondary glazing fitted inside existing windows
• Internal doors
• Commercial or non-residential properties

If you had an extension built and new windows were installed as part of that project, those windows fall under the building control sign-off for the extension, not FENSA. The completion certificate for the extension covers all the work, including the new windows.

FENSA vs CERTASS

CERTASS is another government-authorised competent person scheme for replacement windows and doors. It serves exactly the same regulatory purpose as FENSA: allowing registered installers to self-certify compliance with Part L of the Building Regulations.

From a conveyancing perspective, a CERTASS certificate is equally valid. If your installer provided a CERTASS certificate instead of a FENSA certificate, there is no issue. The buyer's solicitor will accept either.

How to check if your windows are FENSA registered

If you are unsure whether your replacement windows were registered with FENSA, you can check their online database:

1. Visit fensa.org.uk and navigate to the certificate checker.
2. Enter your postcode and select your property address from the results.
3. Review the results. The database will show any FENSA-registered installations at your address, including the date and the installer's name.

The database covers all installations registered from 1 April 2002 onwards. If your windows were installed before this date, they pre-date the requirement for Part L compliance on replacement windows and a FENSA certificate is not applicable. Windows installed before 2002 do not require a FENSA certificate and this should not be raised as a conveyancing issue.

If the check shows no record and you believe the windows were replaced after 2002, the installation was likely carried out by a non-FENSA installer without building control sign-off. This is a common situation that can be resolved, as explained below.

Why FENSA certificates matter when selling

FENSA certificates become relevant during the conveyancing process in two main ways:

The TA6 Property Information Form

Section 6 of the TA6 Property Information Form asks whether any building work or alterations have been carried out at the property and whether the necessary consents and certificates were obtained. Replacement windows fall under this section. As the seller, you must disclose whether windows were replaced and whether you hold the corresponding FENSA, CERTASS, or building control certificate.

The local authority search

The buyer's solicitor orders a local authority search as part of the standard conveyancing searches. This search reveals any building control applications and FENSA or CERTASS notifications lodged for the property. If replacement windows are visible at the property but there is no corresponding record, the solicitor will raise the discrepancy as a pre-contract enquiry.

Mortgage lender requirements

Mortgage lenders follow the UK Finance Mortgage Lenders' Handbook, which requires the buyer's solicitor to report any building work lacking the proper certificates. If FENSA documentation is missing, the lender will typically require either a regularisation certificate from the local authority or an indemnity insurance policy before releasing funds.

What to do if your FENSA certificate is missing

If you are preparing to sell and cannot find your FENSA certificate, there are several paths depending on whether the installation was registered in the first place.

1. Request a duplicate from FENSA

If the installation was registered but you have lost the original certificate, you can request a duplicate directly from FENSA through their website. The fee is typically £5 to £10 per certificate. Use the online database first to confirm the installation is on record.

2. Check with CERTASS or the installer

If the database shows no FENSA record, the installer may have been registered with CERTASS instead. Check the CERTASS database or contact the installation company directly. Some installers keep records of completed jobs and can provide details to help you track down the certificate.

3. Apply for local authority regularisation

If the windows were installed without registration under any competent person scheme and without building control approval, you can apply to your local authority for a retrospective regularisation certificate under regulation 18 of the Building Regulations 2010. The local authority will inspect the windows to confirm they meet Part L requirements. The fee is typically £150 to £400, and the process takes four to eight weeks. For a detailed walkthrough, see our guide on building regulations sign-off missing.

4. Take out indemnity insurance

For window installations completed more than 12 months ago, indemnity insurance is the faster and cheaper option. A one-off policy typically costs £30 to £150 and protects the buyer and their mortgage lender against the financial risk of the local authority taking enforcement action.

The enforcement time limit under Section 36 of the Building Act 1984 is 12 months from the date of completion. After this period, the local authority cannot compel you to remove or alter non-compliant windows. This is why indemnity insurance is both affordable and widely accepted for older installations.

Important: you must not contact the local authority about the windows before arranging indemnity insurance. If building control has been notified or approached, most insurers will not issue a policy. Discuss your options with your solicitor before taking any action.

Regularisation vs indemnity insurance for windows

For most sellers, indemnity insurance is the pragmatic choice when windows were replaced more than a year ago and appear to be in good condition. If the windows are recent, or if you want to provide the buyer with the strongest possible documentation, regularisation is the better route.

FENSA certificate vs window guarantee

A FENSA certificate and a window guarantee are different documents that serve different purposes:

• FENSA certificate — confirms regulatory compliance with Part L of the Building Regulations. Required for conveyancing.
• Window guarantee or warranty — a commercial promise from the manufacturer or installer covering defects in the product or workmanship. Typically valid for 10 to 20 years. Not a regulatory document.

The buyer's solicitor needs the FENSA certificate (or equivalent) to confirm compliance. The guarantee is a bonus that adds value and reassurance but does not replace the regulatory certificate. If you are missing guarantees or warranties for windows or other installations, see our guide on selling a house with missing guarantees. For situations where windows have a guarantee but no FENSA certificate, see our guide on window guarantees without FENSA registration.

Windows installed before 2002

The requirement for replacement windows to comply with Part L of the Building Regulations came into effect on 1 April 2002. If your windows were replaced before this date, FENSA certificates did not exist and were not required. Pre-2002 window replacements are not a conveyancing issue and should not trigger enquiries from the buyer's solicitor.

If there is uncertainty about when the windows were installed, useful evidence includes the original installation invoice, the window guarantee (which typically states the installation date), or a surveyor's assessment of the window age and type. Double-glazed units from the 1990s and earlier are usually identifiable by their design, frame material, and spacer bar style.

How FENSA fits into your property certificate pack

When preparing to sell, your FENSA or CERTASS certificates should be included in the property certificate pack alongside other compliance documents such as the Gas Safe certificate, electrical certificates, and any building control completion certificates. Having these documents gathered and ready before you list avoids delays once the sale is underway.

If you have had multiple sets of windows replaced at different times, you may need separate certificates for each installation. Check the FENSA database for all registered installations at your address and ensure you have documentation for each one.

Common scenarios sellers face

• Windows replaced by a previous owner. You may not know whether the previous owner used a FENSA installer. Check the FENSA and CERTASS databases first. If nothing is registered, indemnity insurance is the usual solution for older installations.
• Installer has gone out of business. The FENSA certificate is independent of the installer's ongoing trading status. If the installation was registered, FENSA holds the record and can issue a replacement certificate regardless of whether the installer is still operating.
• Some windows are FENSA registered, others are not. This happens when windows were replaced at different times by different installers. You need documentation for each installation. Check the databases, obtain duplicates where possible, and arrange indemnity insurance for any unregistered installations.
• Conservatory windows. If the conservatory was built as a new structure, the windows form part of the building control approval for the conservatory itself, not FENSA. If individual conservatory windows were subsequently replaced, those replacements would fall under FENSA in the same way as any other replacement window.

Practical tips for sellers

• Check the FENSA database early. Before you instruct a solicitor, search fensa.org.uk for your property. This takes two minutes and tells you immediately whether there is a gap to address.
• Order duplicate certificates promptly. If installations are registered but you lack the certificates, order duplicates as soon as you decide to sell. The small fee and short wait save significant time later.
• Decide between regularisation and indemnity insurance before contacting anyone. Approaching the local authority about unregistered windows voids the option of indemnity insurance. Speak to your solicitor first so you can make an informed decision.
• Keep records for future owners. Store FENSA certificates, guarantees, and installation invoices with your other property paperwork. Digital copies are a useful backup.

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 scheme: current schemes and types of work
• UK Finance Mortgage Lenders' Handbook — ukfinance.org.uk
• Law Society — TA6 Property Information Form, 4th edition

Frequently asked questions