Extensions

Rules, known as ‘permitted development’ rights, allow you to extend a house without needing to apply for planning permission if specific limitations and conditions are met.

If you want to exceed these, then it is likely that an application for householder planning permission will be required.

If the work adds over 100 square metres of floor space, it may also be liable for a charge under the Community Infrastructure Levy¹.

Please note: These rules apply in the context of the proposed extension and any previous extensions (i.e. the ‘total enlargement’).

These rules apply to houses only and not to:

• Flats and maisonettes (view our guidance on flats and maisonettes²).
• Converted houses or houses created through the ‘permitted development’ rights for:
  • ‘Changes of use’ (Schedule 2, Part 3, Classes G; M; MA; N; P; PA and Q) (as detailed in our change of use section³)
  • ‘New Dwellinghouses’ (Schedule 2, Part 20)
• Other buildings.
• Areas where there may be a planning condition, Article 4 Direction or other restriction that limits or removes ‘permitted development’ rights.

For all extensions

• Only half the area of land around the "original house"* can be covered by extensions or other buildings.
• Extensions cannot be higher than the highest part of the existing roof; or higher at the eaves than the existing eaves.
• Where the extension comes within two metres of the boundary* the height at the eaves cannot exceed three metres.
• Extension cannot be built forward of the ‘principal elevation’ or, where it fronts a highway, the ‘side elevation’.
• The work cannot include:
  • verandas, balconies* or raised platforms.
  • a microwave antenna (e.g. TV aerial or satellite dish).
  • a chimney, flue or soil and vent pipe.
  • any alteration to the roof of the existing house.
• On Article 2(3) designated land* the work cannot include cladding of the exterior.
• The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.

For side extensions

Where it would extend beyond the ‘side elevation’ of the original house*, the extension:

• Cannot exceed four metres in height.
• Can only be a single storey.
• Can only be up-to half the width of the original house*.

On Article 2(3) designated land* all side extensions will require householder planning permission.

For single storey extensions

• Single-storey rear extensions cannot extend beyond the rear wall of the original house* by more than four metres if a detached house; or more than three metres for any other house.
• Where not on Article 2(3) designated land* or a Site of Special Scientific Interest; and subject to ‘prior approval’, the limit for single-storey rear extensions is increased to eight metres if a detached house; or six metres for any other house.
  This requires that the relevant Local Planning Authority is informed of the proposed work via a prior approval application⁴.
• Single-storey rear extensions cannot exceed four metres in height.

For extensions of more than one storey

• Extensions of more than one storey must not extend beyond the rear wall of the original house* by more than three metres or be within seven metres of any boundary* opposite the rear wall of the house.
• Roof pitch must match existing house as far as practicable (note that this also applies to any upper storey built on an existing extension).
• Any upper-floor window located in a ‘side elevation’ must be obscure-glazed; and non-opening (unless the openable part is more than 1.7 metres above the floor).

All side extensions of more than one storey will require householder planning permission.

On Article 2(3) designated land* all rear extensions of more than one storey will require householder planning permission.

Further information

These rules summarise the text of Schedule 2, Part A, Class A of The Town and Country Planning (General Permitted Development) (England) Order 2015⁵ (as amended⁶).

Detailed advice on complying with these rules, illustrative examples and further explanations of the terminology used are provided by the government in the ‘Permitted development rights for householders: technical guidance⁷’.

You are strongly advised to read this guidance to help understand how permitted development rules apply to the specific circumstances of any proposal.

1. https://www.planningportal.co.uk/planning/policy-and-legislation/CIL/about-CIL
2. https://www.planningportal.co.uk/permission/common-projects/flats-and-maisonettes/introduction
3. https://www.planningportal.co.uk/permission/common-projects/change-of-use/use-classes
4. https://www.planningportal.co.uk/permission/common-projects/extensions/prior-approval
5. https://www.legislation.gov.uk/uksi/2015/596/contents
6. http://www.legislation.gov.uk/changes/affected/uksi/2015/596
7. https://www.gov.uk/government/publications/permitted-development-rights-for-householders-technical-guidance