Extensions Planning Permission

For extensions that are likely to fall within permitted development a lawful development certificate is recommended, so that you know your project is compliant and is protected from any retrospective planning issues, enforcements or penalties. Building regulations may also be required depending on the extent of the works.

Large extensions or double-story extensions usually require full planning permission which may be secured through a householder planning application. Flats and maisonettes do not benefit from permitted development rights so in order to extend planning permission is always required.

The following is a brief overview for the planning requirements for each type of extension:

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.
• Extensions cannot be built forward of the principal elevation or, where it fronts a highway, the side elevation.
• The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.
• On designated land all side extensions will require householder planning permission.

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 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 application.
• 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 designated land all rear extensions of more than one storey will require householder planning permission.If there are any constraints that limit or remove permitted development rights or even one of these criteria is not met, then you are required to submit an application for planning permission.

If planning permission is required but the works are completed without first securing the proper planning approval you may face retrospective planning issues. If the local planning authority determine that planning permission was required an enforcement and or penalties may be issued. If planning permission cannot be secured retrospectively the extension may need to be demolished.

If you are in any doubt our expert planning consultants can help. By carrying out a planning appraisal we can advise you on whether planning permission is required, the feasibility, process, timescales, likelihood of success and answer any other questions that you have. Once we know exactly what is required for your project, we will provide you an accurate quote for us to help you.