An extension to your house is one of the ways to enlarge the space you already have. Being that you want a larger kitchen and dining space or a downstairs WCs and utility room, sometimes just by adding a couple of metres on the ground floor makes all the difference. Some of these extensions could be done without any planning permissions as long as you stay within the guidelines laid out by the legislation for you. If you are thinking of doing an extension here are some tips on the Permitted Development Rights regulations that you will have to follow that will be reiterated by your design team.

General information for any extension

  • must not exceed the height of the existing dwelling
  • the extension eaves height must not exceed the existing eaves height must not be more than 50% of the original garden area, including any previous extensions (sheds are included and other outbuildings must be included when calculating the 50% limit)
  • materials should be of similar appearance to the existing house
  • must not include a veranda, balcony or realised platform

Single-storey rear extension

  • maximum height 4 meters
  • must not be more than 3 metres if a attached house and 4 metres if semi-detached beyond the rear wall of the existing house
  • maximum eaves height 3 metres if within 2 metres of the boundary (eaves – point where the wall meets the roof)
Always check with the council because there may be a restriction on the property. It this is the case Planning permission will be required.

Two-storey rear extension

  • Must not be more than 3 metres beyond the rear wall of the original house, and must not be within 7 metres of the rear garden boundary
  • Must not be beyond the side of the original house
  • Must be within 2 metres of any boundary
  • Roof pitch of extensions higher than one storey to match that of the existing house, as far as is practicable
  • Any upper-floor window in a wall or roof slope in a side elevation must be obscure-glazed and non-opening unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed.
Always check with the council because there may be a restriction on the property. It this is the case Planning permission will be required.
One last thing you should double check is, if there are any manholes or sewers running beneath your house or where you want your extension as these could be some complication.
  • Check is there is any manholes as they need to be 3 metres away otherwise you will need approval from Thames Water to ensure that that particular sewerage network will not be compromised.
  • Can get information from Thames Water to check if there is anything underneath your property.
  • If there is, you can either make sure the extension is not compromising the sewer or you will have to get permissions from Thames Water to relocate the sewer system.
By Valerija Kamolina-Corfield Ba(hons) Architecture