Find out about replacing your windows

Use this guide to find information on replacing windows.

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 that 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 as they are a poor substitute for authentic glazing bars and can loosen and fall off, and 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 sill. Section drawings for sash windows should include top rail (including sash box), glazing bar, meeting rail (of both sashes), bottom rail and sill (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
  • delays while additional information is sought.

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