Extension (single storey) An extension or addition to your house is considered to be permitted development, not requiring an application for planning permission, provided certain limits and conditions are met. 1 House designated land - Cladding On designated land* - no cladding of the exterior. Designated land (Article 2(3)) includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites. 2 House designated land - Side extensions On designated land* - no side extensions. Rear extension - No permitted development for rear extensions of more than one storey. The regime for larger single-storey rear extensions (see point 9) does NOT apply to houses on designated land. Designated land (Article 2(3)) includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites. 3 Area permitted No more than half the area of land around the "original house"* would be covered by additions or other buildings. Sheds and other outbuildings must be included when calculating the 50 per cent limit. 4 Fronting highway No extension forward of the principal elevation or side elevation fronting a highway. 5 Materials Materials to be similar in appearance to the existing house. 6 Side extension width Side extensions to be single storey. Width of side extension must not have a width greater than half the width of the original house. 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. 7 Side extension height Side extensions to have a maximum height of four metres and width no more than half that of the original house. 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. 8 Within two metres of the boundary If the extension is within 2m of a boundary, maximum eaves height should be no higher than 3m to be permitted development. 9 Rear extension depth Single-storey rear extensions must not extend beyond the rear wall of the original house* by more than 4m if a detached house; or more than 3m for any other house. Where not on designated land (Article 2(3)) or a Site of Special Scientific Interest, this limit is increased to 8m if a detached house; or 6m for any other house. Find out more. 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. 10 Rear extension height Maximum height of a single-storey rear extension of 4m. 11 Eaves and roof height Maximum eaves and ridge height of extension no higher than existing house. Important note: The permitted development allowances described here apply to houses, not flats, maisonettes or other buildings. You should check with your Local Planning Authority whether permitted development rights apply – they may have been removed by what are known as Article 4 directions. Other consents may be required if your house is listed or in a designated area (Article 2(3)). When planning work you should read all the advice on the Planning Portal under ‘Your responsibilities - Other considerations before you start work’. As well as other important information you will find guidance here on the permitted development regime. Wales: This guidance relates to the planning regime for England. Policy in Wales may differ. Contact your local planning authority for further information. Building Regulations: Most extensions of properties require approval under the Building Regulations. For more information read Planning Portal online guidance. Installation, alteration or replacement of a chimney, flue or soil and vent pipe: Read guidance on the permitted development regime under Class G. Disclaimer: Users should note that this is an introductory guide and is not a definitive source of legal information. Read the full disclaimer. Definitions of terms used in this guide: ‘Original house’ - 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’ - Designated land (Article 2(3)) includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.