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.

• On designated land extensions of more than one storey are not permitted development. * Designated land includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.
• Extensions (including previous extensions) and other buildings must not exceed 50% of the total area of land around 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. * Sheds and other outbuildings must be included when calculating the above 50% limit.

• Maximum eaves and ridge height of extension no higher than existing house. If extension is within two metres of a boundary maximum eaves height should be no higher than three metres to be permitted development.

• Extensions of more than one storey must not extend beyond the rear wall of original house by more than three metres or be within seven metres of any boundary opposite the rear wall of the house.

• Roof pitch of extensions higher than one storey to match that of the existing house, as far as is practicable.

• Materials used in exterior work to be similar in appearance to those of the exterior of the existing house.

• 7. Any upper-floor window in a wall or roof slope in a side elevation must be obscure-glazed and nonopening unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed.

• 8. No balconies or verandas are permitted development.

• 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.
• As well as other important information you will find guidance here on the permitted development regime.

• 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

‘Designated land’ - Designated land (Article 2(3)) includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.