Permitted Development Extension Rules

Extensions are part of modern home ownership, enlarging the living areas and possibly adding an extra bedroom with carefully planned 2 story extensions.

A good extension blends into existing house, or if done correctly can provide a contrasting style which enhances rather than takes away from the original home.

Most home extensions now fall within permitted development so long as they meet the right criteria.

We have covered the permitted development rules and requirements a number of times on our website however extensions are a bit different to other home improvements in that they are often two storeys and are definitely permanent structures.

Whether you require planning permission or not you will still need a qualified architect to draw you up plans and designs for your extension and an experienced builder/contractor to undertake your project.

This guidance reflects temporary increases to the size limits for single-storey rear extensions that must be completed by 30 May 2019, and the associated neighbour consultation scheme.

Under Permitted Development, Extensions must meet the following criteria:

  • No more than half the area of land around the “original house”* can be covered by additions or other buildings.
  • No extension forward of the principal elevation or side elevation fronting a highway.
  • No extension to be higher than the highest part of the roof.
  • Single-storey rear extension must not extend beyond the rear wall of the original house* by more than three metres if an attached house or by four metres if a detached house.
  • Maximum height of a single-storey rear extension of four metres.
  • Extensions of more than one storey must not extend beyond the rear wall of the original house* by more than three metres.
  • Maximum eaves height of an extension within two metres of the boundary of three metres.
  • Maximum eaves and ridge height of extension no higher than existing house.
  • Side extensions to be single storey with maximum height of four metres and width no more than half that of the original house.
  • Two-storey extensions no closer than seven metres to rear boundary.
  • Roof pitch of extensions higher than one storey to match existing house.
  • Materials to be similar in appearance to the existing house.
  • No verandas, balconies or raised platforms.
  • Upper-floor, side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
  • On designated land* no permitted development for rear extensions of more than one storey.
  • On designated land no cladding of the exterior.
  • On designated land no side extensions.

* 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.

  • In addition, outside Article 2(3) designated land* and Sites of Special Scientific Interest the limit is increased to 6m if an attached house and 8m if a detached house until 30 May 2019.
  • These increased limits (between 3m and 6m and between 4m and 8m respectively) are subject to the prior notification of the proposal to the Local Planning Authority and the implementation of a neighbour consultation scheme. If objections are received, the proposal might not be allowed.

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

Please note: The permitted development allowances described here apply to houses and not to:

  • Flats and maisonettes
  • Converted houses or houses created through the permitted development rights to change use
  • Other buildings
  • Areas where there may be a planning condition, Article 4 Direction or other restriction that limits permitted development rights.

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