Adding Storeys to Your House: A Guide to Permitted Development
Class AA of the General Permitted Development Order (GPDO) allows for the enlargement of a dwellinghouse by constructing additional storeys. This is a permitted development right, but it has several restrictions.
What is permitted?
•Up to two additional storeys can be added to an existing house of two or more storeys.
•One additional storey may be added to a bungalow or a single-storey house.
Restrictions on where Class AA applies:
•It does not apply to properties that have been converted from offices, agricultural buildings, storage, light industrial, shops, or casinos under Class O, Class G or Class MA.
•Properties located in a conservation area, an Area of Outstanding Natural Beauty (AONB), the Broads, a National Park, a Heritage site, or on a Site of Special Scientific Interest (SSSI) cannot use Class AA. These are defined as Article 2(3) land.
•If a property was built before 1st July 1948 or after 28th October 2018, it is not eligible for Class AA.
•If the property has already been extended upwards, Class AA does not apply.
•Class AA does not apply to buildings containing one or more flats.
•This right may be removed due to an Article 4 direction or a condition on a previous planning application.
Height restrictions:
•For a detached property, the maximum height for an upward extension is 3.5m on a bungalow or single-story property, or 7m where the existing house has two or three storeys.
•For semi-detached or terraced properties, the extension is limited to 3.5m above the highest part of the adjoining property or the highest part of the terrace.
•The height of any additional storey must not exceed the existing floor-to-ceiling height or 3m, whichever is lower.
Other conditions:
•Extensions must be on the principal part of the house, excluding lower extensions.
•Any strengthening work must be within the property's boundaries and not visible on the exterior.
•Materials used must have a similar appearance to the existing house.
•No new windows are allowed on side elevations, including the roof. The roof pitch must match the existing roof.
•The extended property can only be used as a C3 dwellinghouse, which prohibits a future conversion to a C4 under Class L.
Application process:
•A prior approval application must be made to the local authority. You cannot begin work until prior approval is granted.
•The local authority will assess the impact on neighbouring properties, including overlooking, privacy, and loss of light.
•The design of the property on the principal elevation and any side fronting a highway will also be considered.
•Air traffic and protected view impacts will also be assessed.
•Applicants must provide a report on how the construction will be managed, including hours of operation and how any adverse impact of noise, dust, vibration, and traffic will be mitigated.
•The development must be completed within three years of the prior approval.
•Applications must include drawings showing existing and proposed elevations and window positions.
•The local authority must notify adjoining owners or occupiers about the proposed development. They will also consult on issues like air traffic and protected views.
Additional Points:
•Any planning or permitted development right may be affected by its impact on a European conservation area.
•The information provided is for properties in England; rules are different in Scotland, Wales, and Northern Ireland.
•The information on this website is not considered legal advice. It is the user's responsibility to ensure the information is correct for their situation.