Do replacement windows need Building Regulations approval?

Replacement windows and doors may need to meet Building Regulations and follow the correct certification route. This may be handled by a registered Competent Person Scheme installer or through Building Control, depending on the project and installer status.

Do I always need a FENSA certificate?

Not always. FENSA is one route for qualifying replacement windows and doors, but it does not cover every project type. Some projects may need another Competent Person Scheme route or Building Control approval.

Can you fit windows or doors I have already bought?

Possibly. Fit-only installation is subject to product, opening, access and certification checks before installation is accepted.

Compliance explained before you order

Building Regulations & Certification for Replacement Windows and Doors

Replacement windows and doors are not just about choosing the right frame, colour or handle. In many cases, the installation also needs to meet Building Regulations and follow the correct certification route.

At Green Property Windows & Doors, operated by Green Property Engineering, we explain the likely compliance route before you commit — including whether your project may need a Competent Person Scheme route or Building Control approval.

Ask about certification Send photos or plans

Close-up details of window and door handles, seals, thresholds and trims

Part L, Part F, safety glazing and paperwork responsibilities explained early.

Survey-led advice

Compliance route explained

Part L and Part F considered

Supply & fit or fit-only

Clear responsibilities before installation

Paperwork

Replacement windows and doors need the right route

When external windows or doors are replaced, the work may need to comply with Building Regulations covering thermal performance, safety, ventilation, air supply and means of escape. Some installations can be certified through a registered Competent Person Scheme installer. Others may need Building Control.

We explain the compliance route before you order, not after the job is finished.

We advise on the correct certification route for your project, including Competent Person Scheme or Building Control where required.

Why it matters

It protects the homeowner, the property and the installer

Selling or remortgaging the property

Clear paperwork and agreed responsibilities reduce problems after installation.

Answering solicitor questions later

Clear paperwork and agreed responsibilities reduce problems after installation.

Showing the work was registered where required

Clear paperwork and agreed responsibilities reduce problems after installation.

Dealing with warranties or insurance

Clear paperwork and agreed responsibilities reduce problems after installation.

Checking energy performance requirements

Clear paperwork and agreed responsibilities reduce problems after installation.

Agreeing responsibilities before fit-only work

Clear paperwork and agreed responsibilities reduce problems after installation.

Route 1

Competent Person Scheme

A registered installer under a relevant Competent Person Scheme can self-certify certain types of work instead of the customer applying separately for Building Regulations approval.

For replacement windows and doors, this route is often associated with schemes such as FENSA or Certass, but current registration must always be checked.

Route 2

Building Control

If the work is not being certified through a relevant Competent Person Scheme, approval can usually be sought through the appropriate Building Control body.

This route may be relevant for fit-only work, unusual projects, extensions, new openings, commercial properties, or projects outside a scheme’s scope.

FENSA and scheme wording

FENSA is one route, but it does not cover every project

FENSA is a government-authorised scheme for qualifying replacement windows and doors. It does not cover every project type, and not every installer is FENSA registered.

Claim discipline

We only use FENSA, Certass, CPA, Which? or other accreditation wording if current registration, membership numbers and logo usage rights have been confirmed. Until then, we advise on the correct certification route for your project, including Competent Person Scheme or Building Control where required.

Building Regulations in plain English

Part L: energy performance

Part L is about conserving fuel and power. For windows and doors, that means checking the thermal performance of the full product and how it will be fitted.

Part F: ventilation

Modern windows and doors are more airtight. Background ventilation, including trickle vents or another suitable route, may need to be considered.

Safety glazing

Glazing in critical locations — including doors, glass close to doors and low-level glass — needs checking at survey stage.

Fit-only work

Fit-only installation needs extra clarity

If you have already purchased windows, doors or bifolds, we still need to check whether the product is suitable for the opening and whether the compliance route has been agreed.

Check if fit-only is suitable

For fit-only installations, certification responsibility must be agreed before work starts. We cannot assume responsibility for product specification, manufacturer warranty or Building Control paperwork unless this has been clearly agreed in writing.

Installer checklist