Windows and doors: do I need planning permission?

For a dwellinghouse with normal householder permitted development rights, inserting or replacing windows and doors can often be carried out without a planning application. There are two different reasons why permission may not be needed:

If your question is specifically about changing existing windows – for example the frame material, colour, style or size of an opening – see our separate guide to altering windows.

• ordinary maintenance or repair may not amount to development at all where it does not materially affect the building’s external appearance
• new or altered windows and doors can fall within Part 1 Class A, subject to its limitations and conditions

Window planning permission under Class A

For most dwellinghouses, window planning permission is often supplied by Part 1 Class A where the alteration is development and the Class A requirements are met. Materials used in exterior work normally need to be of a similar appearance to those on the existing dwellinghouse. An upper-floor window in a wall or roof slope forming a side elevation must also be obscure-glazed and non-opening unless the opening parts are more than 1.7 metres above the floor of the room. The GPDO does not prescribe a particular numbered privacy-glass grade.

Rooflights and roof windows are normally considered under Part 1 Class C. Among other requirements, they must not project more than 0.15 metres beyond the plane of the original roof slope, must not be higher than the highest part of the original roof, and side-slope windows are subject to the obscure-glazing and 1.7 metre opening restriction.

Internal secondary glazing which does not alter the exterior is normally an internal alteration rather than a planning matter.

Conservation areas, Article 4 directions and planning conditions

Permitted development rights can be removed by an Article 4 direction or by a condition on a planning permission. Being in a conservation area does not, by itself, remove the ordinary Class A right to alter windows and doors, although an Article 4 direction is more common in some conservation areas and other heritage considerations may be relevant.

There is no separate GPDO rule saying that every window must be identical in size and colour. The relevant Class A condition is that materials used in exterior work are of a similar appearance to those used on the existing dwellinghouse. The more substantial the alteration, the more important it is to check the exact Class A limitations rather than relying on a general ‘like for like’ assumption.

A projecting bay window is an enlargement rather than simply a new window. If it would extend beyond a wall forming the principal elevation of the original dwellinghouse, Class A will not permit it. See our guide to the principal elevation.

It may be appropriate to replace existing windows with new uPVC double-glazed windows or include them in an extension even if there are no such windows in the existing house. What is important is that they give a similar visual appearance to those in the existing house, for example in terms of their overall shape, and the colour and size of the frames.

The wording used in the General Permitted Development order is ‘the materials used in any exterior work (other than materials used in the construction of a conservatory) shall be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse’ 

Listed buildings

If the property is a listed building, the planning-permission question is separate from listed building consent. Replacing or altering windows or doors will require listed building consent where the works would affect the building’s character as a building of special architectural or historic interest. The material, profile, glazing pattern and detailing can therefore matter considerably even where planning permission itself is not required.

Also, if you are a leaseholder, you may need to get permission from your landlord or management company.

Flats

Part 1 householder permitted development rights apply to dwellinghouses, not flats. That does not mean every window repair to a flat needs planning permission: maintenance or a genuinely like-for-like replacement which does not materially affect the external appearance may not amount to development in the first place.

Creating a new opening, materially changing the appearance of windows or doors, or carrying out other external alterations to a flat can require planning permission because there is no Part 1 Class A fallback. Leasehold consent, building regulations and any freeholder requirements are separate issues.

Conservation-area Article 4 directions and listed-building controls can add further restrictions. For a listed building, use the listed-building-consent test rather than assuming that a visually similar replacement is automatically exempt.

Replacing a garage door with a window

Replacing an integral garage door with a window can fall within Part 1 Class A where the building remains a dwellinghouse and the Class A limitations and conditions are satisfied. A conservation-area designation alone does not remove that right, but an Article 4 direction, planning condition or listed-building control may change the answer.

A projecting bay window is different because it enlarges the dwellinghouse. Where it projects beyond a wall forming the principal elevation of the original dwellinghouse, it will not be permitted by Class A.

See our garage conversion guide for the wider planning issues.

Page Updated: 2nd September 2026

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