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How much can I extend my home without planning permission?

Not every extension requires planning permission before you can start building. If you are planning an extension to your house and don’t know whether you will require planning permission or not, then the following guidelines may help.

The rules about whether or not you require planning permission, are contained within a document entitled Permitted Development Rights. The guidelines state the amount of additional space that can be added. When considering what can be built without planning, consideration also needs to be given to the nature of the property and its location.

If the property is listed, then listed building consent will be required in addition to planning permission. Furthermore, planning permission is required if more than half of the land around the original house has been covered by additions or other buildings. The “original house” is defined as the house as it was first built or as it stood on 1st July 1948.

Location also has a bearing. If the property is located on “designated land”, planning permission will be required for any change. “Designated land” includes the National Parks, the Broads, Areas of Outstanding Natural Beauty, Conservation Areas and World Heritage Sites.

What is allowed will depend on the dimensions of the proposal and its position in relation to the house and the boundaries. As a general principle and in order to avoid the need for planning, extensions must not project beyond the front of the principal elevation or an elevation fronting the highway. The ridge height of the extension’s roof must not exceed the height of the main house roof. In addition, materials used must be of similar appearance to those used in the main house. Windows on the side elevation must be obscure glazing, with openings a minimum of 1.7m above floor level.

Side extensions can be single storey or two storey, but must not exceed half the width of the original house. The maximum height of a single storey extension is 4m, but if the extension is within 2m of a boundary, this is reduced to 3m. For a two storey extension within 2m of a boundary, the eaves height must be no greater than 3m.

The pitch of the roof on a 2 storey extension must match that of the main house as reasonably closely as possible. Balconies and verandas are not allowed.

Single storey rear extensions are limited in depth to 3m if terraced or semi detached and 4m if detached. Two storey rear extensions must not extend beyond the rear of the original house by more than 3m or be within 7m of any boundary opposite the rear wall of the house.

The amount of permitted development on single storey extensions has recently been doubled for a three year period extending between 30th May 2013 and 30th May 2016. The maximum depths permitted on single storey rear extensions to terraced and semi detached houses is currently 6m and on detached houses it is 8m. It will be necessary to notify the Local Planning Authority of your intentions.

Garages are generally permitted in your garden or on land around the house without the need for planning permission. Rooflights will not normally require planning permission but bay windows, projecting out of the front elevation will be treated as a front extension.

For roof extensions, 40m3 of additional volume can be added to terraced houses and 50m3 to semi detached or detached houses. This is on the side or rear elevations. Wherever possible, roof extensions, with the exception of hips and gables) should be set back from the eaves by at least 200mm.

There are occasions where Permitted Development rights have been removed. It is not uncommon for this to be the case on modern housing estates. As with all legislation, planning and building regulations change from time to time, so it is always worth seeking professional advice before proceeding.

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