Will I need planning permission for my extension?
An extension or addition to your house is considered to be permitted development, not requiring an application for planning permission, subject to the following limits and conditions:
- No more than half the area of land around the "original house"* would be covered by additions or other buildings.
- No extension forward of the principal elevation or side elevation fronting a highway.
- No extension to be higher than the highest part of the roof.
- Single-storey rear extension must not extend beyond the rear wall of the original house* by more than three metres if an attached house or by four metres if a detached house.
- In addition, outside Article 2(3) designated land* and Sites of Special Scientific Interest the limit is increased to 6m if an attached house and 8m if a detached house until 30 May 2019.
- These increased limits (between 3m and 6m and between 4m and 8m respectively) are subject to the prior notification of the proposal to the Local Planning Authority and the implementation of a neighbour consultation scheme. If objections are received, the proposal might not be allowed.
- Maximum height of a single-storey rear extension of four metres.
- Extensions of more than one storey must not extend beyond the rear wall of the original house* by more than three metres.
- Maximum eaves height of an extension within two metres of the boundary of three metres.
- Maximum eaves and ridge height of extension no higher than existing house.
- Side extensions to be single storey with maximum height of four metres and width no more than half that of the original house.
- Two-storey extensions no closer than seven metres to rear boundary.
- Roof pitch of extensions higher than one storey to match existing house.
- Materials to be similar in appearance to the existing house.
- No verandas, balconies or raised platforms.
- Upper-floor, side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
- On designated land* no permitted development for rear extensions of more than one storey.
- On designated land no cladding of the exterior.
- On designated land no side extensions.
* The term "original house" means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.
* Designated land includes conservation areas, national parks and the Broads, Areas of Outstanding Natural Beauty, and World Heritage Sites.
Please note: The permitted development allowances described here apply to houses and not to:
- Flats and maisonettes
- Converted houses or houses created through the permitted development rights to change use
- Other buildings
- Areas where there may be a planning condition, Article 4 Direction or other restriction that limits permitted development
How much does an extension cost?
The cost of your extension will be affected by many variables, from soil type (which impacts the foundations); whether you are building a single or two storey extension; what the extension will be used for; to how much glazing you plan to specify.
Depending where you are in the UK, for a straightforward extension you should allow around £1,000–2,000/m².
original article from www.planningportal.co.uk