No FENSA Certificate for Windows: What to Do When Selling

Replacement windows are one of the most common home improvements in England and Wales. They improve energy efficiency, reduce noise, and can add value to your property. But if the work was done without a FENSA certificate, a CERTASS certificate, or a local authority completion certificate, it can create a problem when you come to sell.

This guide explains what FENSA is, why it matters during a property sale, and exactly what to do if you discover your windows do not have the right paperwork. In most cases, this is a solvable issue that should not derail your transaction — provided you deal with it early and choose the right route.

What is FENSA?

FENSA (Fenestration Self-Assessment Scheme) is a government-authorised competent person scheme that allows registered window and door installers in England and Wales to self-certify that their work complies with Building Regulations. It has been operating since 2002 and is managed by the Glass and Glazing Federation (GGF).

When an installer registered with FENSA fits replacement windows or external doors, they notify the local authority on your behalf and issue you with a certificate confirming the work meets Building Regulations Part L (conservation of fuel and power). This certificate is the proof that the installation was done to the required energy efficiency standard.

FENSA is not the only route to compliance. Installers can also be registered with CERTASS, another government-authorised competent person scheme that serves exactly the same purpose. A CERTASS certificate is equally valid. Alternatively, the homeowner can arrange for the local authority's own building control team to inspect and sign off the work, although this is less common because it involves a separate application and fee.

Why replacement windows need Building Regulations sign-off

Since 1 April 2002, the replacement of windows and external doors in England and Wales has been classed as building work that must comply with the Building Regulations, specifically Part L (conservation of fuel and power). This requirement was introduced to improve the energy performance of the existing housing stock.

The regulations require that replacement glazing meets minimum thermal performance standards — currently a Window Energy Rating (WER) of band C or a centre-pane U-value of 1.4 W/m²K or better. They also cover ventilation requirements and, where applicable, means of escape in case of fire.

Compliance must be demonstrated in one of three ways:

• A certificate from a FENSA-registered installer
• A certificate from a CERTASS-registered installer
• A completion certificate from the local authority's building control department

If none of these exists for windows replaced after April 2002, the work is technically non-compliant. This is the situation that creates issues during a property sale. For a broader overview of what documentation sellers need, see our guide on documents needed to sell a house.

How missing FENSA certificates come to light during a sale

When you sell a property, the buyer's solicitor will review the title documents, the property information forms (TA6), and the results of their searches. As part of the standard conveyancing enquiries, they will ask whether any building work has been carried out at the property and whether the appropriate certificates and approvals were obtained.

Replacement windows are one of the most commonly flagged items. The buyer's solicitor will typically check:

• Whether the TA6 form discloses any replacement windows or doors
• Whether FENSA, CERTASS, or local authority building control certificates are included in the contract pack
• Whether the local authority search results show any building control applications for window replacements

If windows have clearly been replaced (they look newer than the property, they are double-glazed in a period home, or the seller has disclosed the work on the TA6) but there is no certificate, the buyer's solicitor will raise an enquiry. The buyer's mortgage lender may also flag it as a condition of the loan. This is the point at which many sellers first realise there is a problem. For more on how missing approvals surface, see our guide on building regulations sign-off missing.

What to do if you have no FENSA certificate

If your replacement windows do not have a FENSA certificate, a CERTASS certificate, or a local authority completion certificate, you have three main options. The right choice depends on the age of the windows, whether you have already contacted the council, and how quickly you need to resolve the issue.

Option 1: Check whether a certificate already exists

Before assuming the worst, check whether the installation was actually certified but the paperwork has been lost. You can:

• Search the FENSA database at fensa.org.uk using your postcode and address. If a record exists, you can order a replacement certificate.
• Search the CERTASS database at certass.co.uk. If the installer was CERTASS-registered rather than FENSA-registered, the certificate will appear here.
• Contact your local authority building control department and ask whether they hold a completion certificate for window work at your address. If the installer submitted a building notice or the homeowner applied directly, the council should have records.

Option 2: Take out indemnity insurance

Indemnity insurance is the most common solution when a FENSA certificate is missing. It is a one-off insurance policy that protects the buyer and their mortgage lender against the financial risk of the local authority taking enforcement action over non-compliant building work.

Key points about indemnity insurance for missing window certificates:

• The cost is typically £30 to £100 for a one-off policy, depending on the property value and the insurer
• The policy lasts indefinitely and passes to future owners of the property
• It is arranged by your solicitor and can usually be put in place within 24 to 48 hours
• The seller normally pays for the policy as part of the sale
• Critical condition: you must not have contacted the local authority about the windows before taking out the policy. If you have already made an enquiry or application to the council about the work, most insurers will refuse to cover it

Indemnity insurance is accepted by the vast majority of mortgage lenders and is the standard solution recommended by conveyancers when the windows are already installed and appear to be of reasonable quality. It does not prove the windows comply with Building Regulations — it simply insures against the consequences if they do not.

Option 3: Apply for a regularisation certificate

If you prefer formal sign-off — or if indemnity insurance is not available because you have already contacted the council — you can apply to your local authority for a regularisation certificate. This is a retrospective Building Regulations approval under Section 36 of the Building Act 1984.

The process involves:

1. Submitting a regularisation application to your local authority building control department
2. Paying the application fee, which is typically £250 to £500 depending on the council
3. A building control officer visiting the property to inspect the windows
4. If the windows meet the required standard, the council issues a regularisation certificate

The main drawback is time. The process can take four to eight weeks, and there is a risk that the windows may not pass inspection — for example, if the thermal performance is below the required standard or the ventilation provisions are inadequate. If the windows fail, you may need to carry out remedial work before the certificate can be issued, which adds further cost and delay.

For a detailed explanation of how regularisation works more broadly, see our guide on no building regulations certificate.

Indemnity insurance vs regularisation: which should you choose?

The choice between indemnity insurance and regularisation depends on your circumstances. Here is a comparison to help you decide:

In practice, indemnity insurance is the route chosen in the vast majority of residential property sales where a FENSA certificate is missing. It is fast, cheap, and widely accepted. The only situations where regularisation is typically necessary are where the seller has already contacted the council (invalidating the insurance option), where the buyer specifically insists on formal compliance, or where there are genuine concerns that the windows may be unsafe or seriously non-compliant.

When a missing FENSA certificate is not an issue

Not every property with replacement windows needs a FENSA certificate. There are several situations where the absence of a certificate is not a problem:

• Windows installed before 1 April 2002. The Building Regulations requirement for replacement windows only applies to installations from this date onwards. If your windows were fitted before April 2002, no certificate is needed and this should not be raised as an issue during the sale.
• Like-for-like repairs. If you repaired existing windows rather than replacing them (for example, replacing broken glass within the existing frames), this is maintenance rather than building work and does not require Building Regulations sign-off.
• New-build properties. If the windows were part of the original construction, they would have been covered by the building control sign-off for the entire new build. A separate FENSA certificate is not required.
• Listed buildings. Replacement windows in listed buildings require listed building consent rather than (or in addition to) Building Regulations approval. The compliance paperwork is different in these cases.

CERTASS: the other competent person scheme

FENSA is the best-known window certification scheme, but it is not the only one. CERTASS (Certificate of Assurance) is another government-authorised competent person scheme that serves exactly the same function. Both schemes are recognised by the Department for Energy Security and Net Zero (formerly BEIS) and are listed as approved competent person schemes under the Building Regulations.

A CERTASS certificate carries the same legal weight as a FENSA certificate. If your installer was registered with CERTASS, the certificate they issued is valid proof of Building Regulations compliance. The buyer's solicitor should accept it without question. If they query it, your solicitor can confirm that CERTASS is a government-authorised scheme with the same standing as FENSA.

What the buyer's solicitor will ask

If your property has replacement windows, expect the buyer's solicitor to raise specific enquiries as part of the standard conveyancing enquiries process. Typical questions include:

• When were the windows replaced and by whom?
• Was the installer registered with FENSA, CERTASS, or another competent person scheme?
• Can you provide the FENSA or CERTASS certificate, or a local authority completion certificate?
• If no certificate is available, will the seller provide indemnity insurance?
• Have you contacted the local authority about the windows?

Having your answers and documentation ready before these questions arrive will save time. If you already know the certificate is missing, instruct your solicitor to arrange indemnity insurance as part of your sale preparation. This way, you can provide the policy alongside the contract pack and avoid a round of additional enquiries that could add one to two weeks to your timeline.

How to avoid this problem in the first place

If you are having windows replaced now or in the future, protecting yourself is straightforward:

1. Use a FENSA or CERTASS-registered installer. Check their registration on the relevant scheme's website before signing a contract. This is the simplest way to ensure you get the right paperwork.
2. Keep the certificate safe. When the work is complete, the installer should provide a certificate confirming Building Regulations compliance. File it with your other property documents — you will need it when you sell.
3. If using a non-registered installer, notify building control. If your chosen installer is not registered with FENSA or CERTASS, you (or they) must submit a building notice to your local authority before the work starts. The council will inspect the work and issue a completion certificate.

The role of your solicitor

Your conveyancing solicitor plays a central role in resolving a missing FENSA certificate. For an overview of what solicitors charge for this type of work, see our guide to solicitor fees for selling a house. They will:

• Advise whether indemnity insurance or regularisation is the better route for your specific situation
• Source and arrange the indemnity insurance policy if that is the chosen approach
• Draft appropriate replies to the buyer's solicitor's enquiries about the windows
• Include the insurance policy or regularisation certificate in the contract pack so the buyer's side has everything they need

If you are preparing your property for sale and you know the FENSA certificate is missing, raise it with your solicitor at the outset. Dealing with it proactively, rather than waiting for the buyer's solicitor to flag it, keeps the transaction on track and avoids unnecessary delays.

Sources

• FENSA (Fenestration Self-Assessment Scheme) — fensa.org.uk
• CERTASS (Certificate of Assurance) — certass.co.uk
• GOV.UK — Building Regulations: Approved Document L (Conservation of fuel and power)
• GOV.UK — Competent person scheme: current schemes and what they cover
• Building Act 1984, Section 36 (regularisation of unauthorised building work) — legislation.gov.uk
• The Building Regulations 2010 (SI 2010/2214) — legislation.gov.uk
• Law Society Conveyancing Protocol, 5th edition — lawsociety.org.uk

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