Double and triple glazed windows
Installing replacement windows, which do not materially change the external appearance of the existing building, including the overall shape, colour and size of the window frames, or installation of internal secondary glazing, may be permitted development with no need to apply to the council for planning permission.
There are, however, important limits and conditions to permitted development rights, which must be met to benefit from these rights. For information on permitted development rights, visit the interactive guidance on the Planning Portal website.
If you believe your proposed works to windows would be lawful under the permitted development regulations, and you require written confirmation from the council that the work does not need planning permission, you are advised to submit an application for a lawful development certificate.
If your installation does not meet the government requirements, you will need to apply for planning permission.
In very general terms, planning permission is required for most external alterations to flats and maisonettes (and most non-residential properties), irrespective of whether they are purpose-built or conversions.
Further advice on double or triple glazed windows can be found via the:
- Lambeth Design Guide - Building Alterations, Extensions and Retrofit (PDF 2.7MB)
- Planning Portal - glazing
- Energy Saving Trust - windows and doors
If your property is in a conservation area and/or is a statutory listed building, please also refer to the windows and doors advice on the Historic England website.