Do You Need Planning Permission to Add a Window UK?

In most cases, replacing existing windows with new ones of a similar appearance does not require planning permission, as it falls under Permitted Development Rights. However, you will need planning permission if your home is a listed building (Listed Building Consent is required), if your property is in a conservation area with an Article 4 Direction in place, or if the replacement significantly alters the window's external appearance. All replacement windows must still comply with Building Regulations covering thermal efficiency, safety glazing, ventilation, and means of escape. Using a FENSA-registered installer simplifies the compliance process.

Adding a completely new window opening where none previously existed is more likely to require planning permission than simply replacing an existing window. Under Permitted Development Rights, new windows on upper-floor side elevations must typically be obscure-glazed and non-opening if below 1.7 metres from the internal floor level, to protect neighbours' privacy. New windows on rear elevations at ground level are generally permitted. For front-facing elevations, the rules are stricter. The specific requirements depend on your property type and location, so always check with your local planning authority before cutting a new opening.

Conservation areas have stricter controls to preserve their special architectural character. Replacing windows in a conservation area may require planning permission, particularly if the changes affect the principal elevation or any elevation facing a highway. If an Article 4 Direction is in place, even like-for-like replacements may need permission. The local authority will typically require that replacement windows match the original style, proportions, and materials. Timber windows are often preferred or required over uPVC in conservation areas. Always consult your local council's planning department before proceeding with any window work in a conservation area.

All replacement windows in the UK must comply with Building Regulations regardless of whether planning permission is needed. Key requirements include thermal efficiency with a maximum U-value of 1.4 W/m2K for windows, adequate ventilation through trickle vents or equivalent, safety glazing in critical locations such as doors and low-level panes, and fire escape provisions for windows serving habitable rooms. Windows must also not compromise the structural integrity of the wall. A FENSA or Certass registered installer can self-certify compliance, or you can apply directly to your local authority Building Control department.

Yes, if your property is a listed building (Grade I, II*, or II), you will almost certainly need Listed Building Consent before replacing or altering any windows. This applies even to like-for-like replacements, as the consent process ensures changes preserve the building's historical and architectural significance. Unauthorised alterations to a listed building are a criminal offence. Applications are made through your local planning authority, and you may need to provide detailed specifications showing how the new windows will match the originals. Bespoke timber windows that replicate original designs are typically required for listed properties.

If you replace windows without required planning permission or Listed Building Consent, you could face serious consequences. The local authority can issue an enforcement notice requiring you to restore the windows to their original state at your own expense. For listed buildings, carrying out unauthorised work is a criminal offence that can result in prosecution and unlimited fines. Even without enforcement action, lack of proper permissions or Building Regulations compliance certificates can cause problems when selling your property. Buyers and their solicitors will check for these certificates, and their absence can delay or derail a sale.

FENSA (Fenestration Self-Assessment Scheme) is a government-authorised scheme that allows registered window installers to self-certify that replacement windows comply with Building Regulations. When you use a FENSA-registered installer, they notify your local authority on your behalf and provide a FENSA certificate as proof of compliance. This certificate is important when selling your property, as buyers' solicitors will request evidence of Building Regulations compliance. If you use a non-FENSA installer, you must arrange a separate Building Control inspection and pay additional fees. Always check that your installer is FENSA or Certass registered.

Under Permitted Development Rights, you can generally replace windows with a different style provided the new windows are of a similar external appearance to the originals. Minor changes such as switching from a top-hung to side-hung casement are usually acceptable. However, significant changes such as converting sash windows to casement windows, changing the proportions, or altering materials from timber to uPVC may require planning permission, especially in conservation areas or on prominent elevations. For properties with no special designations, there is more flexibility, but substantial changes to the front elevation may still need approval.