Do you need planning permission to replace windows and doors?

the materials used in any exterior work (other than materials used in the construction of a conservatory) must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse

What "similar appearance" means

The government's technical guidance says the materials need not be the same, only similar in appearance. It gives uPVC as an example: new uPVC double-glazed windows can be acceptable even where the house has none, if they look similar to the existing windows in overall shape and in the colour and size of the frames.

Two things fall outside this right. A new bay window is treated as an extension, not a window (Planning Portal), so the Class A extension limits apply to it. A window in the roof is a rooflight under Class C.

Upper-floor side windows

Any upper-floor window in a wall or roof slope forming a side elevation must be obscure-glazed, and non-opening unless the parts that open are more than 1.7 metres above the floor of the room (A.3(b)). The technical guidance sets obscure glazing at level 3 or above on the usual 1 to 5 privacy scale, and says one-way glass does not count. On a staircase or landing the 1.7 metres is measured from the stair or landing below the centre of the window.

Conservation areas, Article 4 and listed buildings

Being in a conservation area does not by itself remove this right. The extra Class A restrictions for Article 2(3) land cover cladding, side extensions and rear extensions of more than one storey, not windows and doors (A.2). What matters is whether the council has made an Article 4 direction withdrawing Class A rights for windows and doors on your street (article 4(1)). If it has, you need to apply.

A listed building needs listed building consent for any works that would affect its character, inside or out, and works without consent are a criminal offence (sections 7 and 9 of the Planning (Listed Buildings and Conservation Areas) Act 1990). There is no application fee. Windows and doors in conservation areas and listed buildings covers both in detail.

Flats

Part 1 of the Order applies to houses only: "dwellinghouse" excludes flats (article 2(1)). New windows that materially change the appearance of a block of flats need planning permission. See flats and maisonettes.

Building Regulations

An external window or door is a controlled fitting, and fitting one is building work (regulation 3(1)(b) of the Building Regulations 2010). An installer registered with a competent person scheme, such as FENSA or CERTASS, can certify a replacement window or door in an existing home (Schedule 3, paragraph 10). Otherwise you apply to building control. A replacement window should give at least the same means of escape as the one it replaces (Planning Portal).

What this means for you

Match the look of what is there, keep new upstairs side windows obscured, and check for an Article 4 direction before you order. The permitted development checker asks the designation questions.

Getting certainty

If you are unsure whether a new design is "of a similar appearance", a lawful development certificate for proposed works settles it. From 1 April 2026 the fee for householder works is £274, and the council has 8 weeks to decide.