The short answer
- Replacement windows and doors in a home must meet the Building Regulations. Either an installer registered with a competent person scheme certifies the work, or you apply to building control.
- FENSA is the best-known scheme. CERTASS, Certsure, NAPIT, Blue Flame Certification and ASSURE also cover replacement windows and doors.
- The schemes cover replacements in existing homes. New extensions and new or widened openings go through building control.
- The certificate proves compliance. It is not a guarantee.
1. How competent person schemes work
Competent person schemes are authorised by the government. Their registered installers can self-certify that their work meets the Building Regulations, so you don’t have to apply to building control yourself. The installer registers the job with the scheme, the council is notified, and you receive a certificate for the work.
2. What the schemes cover, and what they don’t
For homes, the schemes cover replacement windows, doors, roof windows and rooflights in an existing dwelling. They don’t cover:
- new homes and new extensions, including the doors and windows in them;
- conservatories and porches;
- new or widened openings, which need a beam and structural approval;
- repairs where the frame is not replaced, and commercial buildings.
Those go to building control, which checks the work and issues a completion certificate.
3. What the work has to meet
Whoever certifies it, a replacement window or door has to meet Part L for energy (a U-value of 1.4 W/m²K or better, or Window Energy Rating band B), keep ventilation and escape at least as good as before, use safety glass in critical locations, and be properly supported over the opening. Our replacing windows guide explains each one.
4. Certificates when you sell
Your buyer’s solicitor will ask for certificates for windows and doors replaced since 2002. If you can’t find one:
- search for it, or order a copy, on the FENSA website, or ask the scheme the installer used;
- ask the council’s building control team for its records of the work;
- if the work was never certified, the council can sometimes issue a regularisation certificate after inspecting it.
Solicitors sometimes suggest indemnity insurance instead. It covers the risk of enforcement action, not the quality of the windows.
5. Certificates and guarantees
A certificate shows the work met the Building Regulations when it was done. It isn’t a guarantee of the product or the fitting. Ask the installer what guarantee they give, what it covers, and what happens if the company stops trading: an insurance-backed guarantee covers that case.
Before you sign, check the installer’s registration on the scheme’s website. For work the schemes don’t cover, ask who will apply to building control.
Questions
Do I need a FENSA certificate?
You need proof that replacement windows and doors meet the Building Regulations: a certificate from FENSA or another competent person scheme, or a completion certificate from building control. Your buyer’s solicitor will ask for it.
What if I can’t find my FENSA certificate?
Search for it or order a copy on the FENSA website. If another scheme was used, ask that scheme, or ask the council’s building control team for its records.
Does FENSA cover bi-fold doors in a new extension?
No. Competent person schemes cover replacements in existing homes. Doors in a new extension, and new or widened openings, go through building control.
Is a FENSA certificate a guarantee?
No. It shows the installation met the Building Regulations. The guarantee comes from the installer; ask what it covers and whether it is insurance-backed.
Sources
The official documents this guide is based on. Check the current edition before you order.