Extensions

Planning Permission

New regulations came into force on 30 September 2013 which changed the building work which can be done without needing to apply for planning permission. The Welsh Government has produced a technical guide, and a householder guide, available here, to help you understand how permitted development rules might apply to your circumstances.

An extension or addition to your house is considered to be permitted development, not requiring an application for planning permission, subject to limits and conditions. There are different limits and conditions for rear extensions and side extensions, and for single storey and extensions of more than one storey.  

All Extensions

  • No extension can be constructed in front of the principal elevation of your house.
  • No more than half of the area of land around the original house can be covered by an extension.
  • The extension cannot be higher than the highest part of the roof of the existing dwelllinghouse
  • The extension cannot be higher than the height of the eaves of the existing dwellinghouse.
  • If your extension is located within 2 metres of a boundary of your house, the eaves height of the extension cannot exceed 3 metres.
  • If your extension is within 2 metres of a boundary of your house, it cannot exceed 4 metres in height.
  • The appearance of the materials used in the extension must, as far as possible, match those used for your existing home.
  • You may not build verandas, raised platforms, roof terraces or balconies.  A  Juliet balcony  that has no platform, does not project from the extension by more than 300mm, is not within 10.5m of the side boundary of your house, and is not fixed to the principal elevation of your house is permitted.  Shutters on the principal elevation of your house are not permitted.

Single storey rear extensions

  • Single storey extensions must not extend beyond the rear wall of our house by more than 4 metres, and cannot exceed 4 metres in height

Rear extensions with more than one storey

  • The ground floor part of the extension cannot extend beyond the rear wall of the house by more than 4 metres
  • The upper floor part of the extension cannot extend beyond the rear wall of the house by more than 3 metres
  • The distance between the rear wall of the extended part of the house and the rear boundary of the house, normally the rear garden fence or wall, must be at least 10.5 metres
  • Any upper floor window in the side elevation of the extension must be obscure glazed and non-opening, unless the window is 1.7 metres above floor level
  • The roof pitch of the extension must, as far as it practical, match the pitch of the existing dwellinghouse
  • Rear extensions of more than one storey are not permitted in a conservation area, national park, an area of outstanding natural beauty or a World Heritage Site

Single storey side extensions

  • Single storey side extensons cannot be closer to a highway than any wall in the side elevation of the existing dwellinghouse, or at least 10.5 metres from the highway, whichever is nearest the highway
  • Single storey side extensions cannot exceed 4 metres in height
  • The width of the widest part of the resulting dwellinghouse cannot exceed the width of the widest part of the original dwellinghouse by more than 50%
  • When the house is located in a conservation area, national park, an area of outstanding natural beauty or a World Heritage Site, the extension must not project from the side elevation of the house by more than 3 metres and must be set back from the principal elevation of the dwellinghouse by a least 1 metre

Side extensions with more than one storey

  • Side extensions with more than one storey cannot be closer to a highway than any wall in the side elevation of the existing dwellinghouse or at least 10.5 metres from the highway, whichever is nearest the highway
  • The extension is not permitted within 10.5 metres of a side boundary of the house
  • The extension must be set back from the principal elevation of the house by at least 1 metre
  • The width of the widest part of the resulting dwellinghouse cannot exceed the width of the widest part of the original dwellinghouse by more than 50%
  • Any upper floor window in the side elevation of the extension must be obscure glazed and non-opening, unless the window is 1.7 metres above floor level
  • The roof pitch of the extension must, as far as it practical, match the pitch of the existing dwellinghouse
  • Side extensions with more than one storey are not permitted when the house is located in a conservation area, national park, an area of outstanding natural beauty or a World Heritage Site

Please note: the permitted development allowances described here apply to houses not flats, maisonettes or other buildings. View guidance on flats and maisonettes here.

Installation, alteration or replacement of a chimney, flue or soil and vent pipe: Read guidance on the permitted development regime under Class G of the regime.

Please be aware that if your development is over 100 sqm, it may be liable for a charge under the Community Infrastructure Levy.

* The term "original house" means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.

* Designated land includes national parks, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.

Disclaimer - Wales

This is an introductory guide and is not a definitive source of legal information. This guidance relates to the planning regime for Wales. Policy in England may differ. If in doubt contact your Local Planning Authority.

Read the full disclaimer here.