Depending on the planning constraints on the property and the appearance of the proposed windows, you may or may not need planning permission from the council to replace the windows in your property.

Sections in this guide (click title to view)

1. Replacing the windows in a house

Most houses have permitted development rights, which make it possible to replace existing windows (or create new windows) without requiring planning permission from the council, so long as:

  • The materials of the proposed windows are 'of a similar appearance' to the materials of the existing windows, and
  • Any upper floor side windows are obscure-glazed and non-opening. (Note that the non-opening requirement does not apply if the parts of the window that can be opened would be more than 1.7m above internal floor level).

If the proposal does not comply with points above then planning permission will be required.

Not all houses have permitted development rights. Sometimes these rights have been removed by a condition attached to a previous planning permission or by an article 4 direction. In addition, if your property is statutory listed, you will not have permitted development rights and you will require planning permission as well as listed building consent to change your windows.

If permitted development rights have been removed or the building is statutory listed, then planning permission will be needed and you should take into account our requirements for the replacement windows:

  • In order to protect the character of the building, any replacement windows should replicate the appearance, detailing and opening type of the originals. This is particularly important on heritage assets. If replacement windows for heritage assets do not accurately reproduce the originals, permission is likely to be refused and retention of the originals sought. Exemptions from the building regulations are available on heritage assets to ensure new work does not harm the special interest of the building.
  • Replacement windows generally have to comply with thermal insulation standards as set out in Building Regulations. To meet these standards new windows will usually need to be double glazed, although there are exemptions for heritage assets. It is especially important that the new windows match the originals that they replace where the building is part of a terrace or group which shares common window detailing. Similarly, the windows of individual flats are often identical to those within the whole building to give unity of design.

As a general rule replacement windows should:

  • Fit neatly into existing openings, recessed into the established reveal depth.
  • Follow the original style of opening - such as sliding sash or hinged casement.
  • Replicate frame dimensions and detailing as closely as possible. ‘Stick on’ or non-integral glazing bars should be avoided—they are a poor substitute for authentic glazing bars and can loosen and fall off. Glazing should generally have a treatment externally which accurately reproduces a traditional putty finish.
  • Have unobtrusive, security rated locks and fittings.
  • Avoid visually obtrusive trickle-vents on heritage assets.
  • Be of the same material as the original windows on heritage assets.

Planning applications and listed building applications for replacement windows should contain detailed drawings (1:20 scale elevations and larger scale 1:5 or 1:2 detailed cross sections) of the original and proposed windows, for ease of comparison. The cross sections should show how the window unit sits within the window reveal and relates to the existing cill. Section drawings for sash windows should include top rail (including sash box), glazing bar, meeting rail (of both sashes), bottom rail and cill (including sash box). A listed building consent application will also need to be accompanied by a condition report of the window.

A failure to include adequate information can result in an application being considered invalid; a refusal of permission on the basis of insufficient information; or delays, while additional information is sought.

The Planning Portal also has further useful planning and building regulations guidance on replacing windows and doors.

2. Replacing the windows in a flat

Flats do not have permitted development rights for changes to windows. If the design, method of opening, materials and profile of the replacement windows are not the same as the existing windows, then planning permission will normally be required. If your building is statutory listed you will also require listed building consent.

If you need to apply for planning permission and/or listed building consent, then please check that your proposal complies with the following guidelines:

  • In order to protect the character of the building, any replacement windows should replicate the appearance, detailing and opening type of the originals. This is particularly important on heritage assets. If replacement windows for heritage assets do not accurately reproduce the originals, permission is likely to be refused and retention of the originals sought. Exemptions from the building regulations are available on heritage assets to ensure new work does not harm the special interest of the building.
  • Replacement windows generally have to comply with thermal insulation standards as set out in Building Regulations. To meet these standards new windows will usually need to be double glazed, although there are exemptions for heritage assets. It is especially important that the new windows match the originals that they replace where the building is part of a terrace or group which shares common window detailing. Similarly, the windows of individual flats are often identical to those within the whole building to give unity of design.

As a general rule replacement windows should:

  • Fit neatly into existing openings, recessed into the established reveal depth.
  • Follow the original style of opening - such as sliding sash or hinged casement.
  • Replicate frame dimensions and detailing as closely as possible. ‘Stick on’ or non-integral glazing bars should be avoided—they are a poor substitute for authentic glazing bars and can loosen and fall off. Glazing should generally have a treatment externally which accurately reproduces a traditional putty finish.
  • Have unobtrusive, security rated locks and fittings.
  • Avoid visually obtrusive trickle-vents on heritage assets.
  • Be of the same material as the original windows on heritage assets.

Planning applications and listed building applications for replacement windows should contain detailed drawings (1:20 scale elevations and larger scale 1:5 or 1:2 detailed cross sections) of the original and proposed windows, for ease of comparison. The cross sections should show how the window unit sits within the window reveal and relates to the existing cill. Section drawings for sash windows should include top rail (including sash box), glazing bar, meeting rail (of both sashes), bottom rail and cill (including sash box). A listed building consent application will also need to be accompanied by a condition report of the window.

A failure to include adequate information can result in an application being considered invalid; a refusal of permission on the basis of insufficient information; or delays, while additional information is sought.

The Planning Portal also has further useful planning and building regulations guidance on replacing windows and doors.

3. Improving windows without need for planning approval

The refurbishment and draught-proofing of existing windows can improve their thermal performance. Similarly, the installation of internal secondary glazing can also significantly improve thermal performance and sound insulation. These works do not require planning permission.

Internal secondary glazing is generally supported on listed buildings but may require listed building consent depending on its impact on the special interest of the building.