Loft conversion (roof extension)

1. Loft conversions are NOT permitted development for houses on designated land.

2. To be permitted development any additional roof space created must not exceed these volume allowances:

  • 40 cubic metres for terraced houses.

  • 50 cubic metres for detached and semi-detached houses.

Bear in mind that any previous roof space additions must be included within this volume allowance. Although you may not have created additional space a previous owner may have done so.

3. An extension beyond the plane of the existing roof slope of the principal elevation that fronts a highway is NOT permitted development.

4. Materials to be similar in appearance to the existing house.

5. No part of the extension to be higher than the highest part of the existing roof.

6. Verandas, balconies or raised platforms are NOT permitted development.

7. Any side-facing windows 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.

8. Roof extensions, apart from hip to gable ones, to be set back, as far as is practicable, at least 20cm from the original eaves. The 20cm distance is measured along the roof plane.
The roof enlargement cannot overhang the outer face of the wall of the original house.
Note: For an explanation of how to apply the 20cm set back condition please see pages 35-36 of ‘Permitted development for householders – Technical guidance’ (PDF).

9. Work on a loft or a roof may affect bats. You need to consider protected species when planning work of this type. A survey may be needed, and if bats are using the building, a licence may be required.
Contact Natural England for more advice.
View specific information regarding Bats.

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.
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: Building regulations approval is required to convert a loft or attic into a liveable space. 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:
‘Designated land’ - Designated land includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.