Extensions (single storey)

Planning Permission

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. Whereas we can advise, only the planning department can say for certain that a proposal is PD. When in doubt, we recommend applying for a certificate of lawful proposed development (CoLU) to confirm your project is PD.

The rules are:

  1. 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. 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.
  3. 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. 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.
  4. No extension forward of the principal elevation or side elevation fronting a highway.
  5. Materials to be similar in appearance to the existing house.
  6. Side extensions to be single storey. Width of side extension must not have a width greater than half the width of the original house.
  7. Side extensions to have a maximum height of four metres and width no more than half that of the original house.
  8. If the extension is within 2m of a boundary, maximum eaves height should be no higher than 3m to be permitted development.
  9. 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.
  10. Maximum height of a single-storey rear extension of 4m.
  11. Maximum eaves and ridge height of extension no higher than existing house.

Planning Cost Calculator

  • Immediate estimate for planning your project
  • Accurate quote emailed within the hour
  • Planning appraisal report emailed to you the same day
  • Consultation call with a Planning Consultant within 24 hours
Get FREE estimate