Some small extension are now exempt from the planning process, listed below are the guidelines that came into effect as of 1st October 2008.  In most cases full building regulations drawings are still required. 

Planning Permission

Under new regulations that came into effect on 1 October 2008 an extension or addition to your home is considered to be permitted development, not requiring an application for planning permission, subject to the following limits and conditions:

Building extension guidelines:-

• 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.
• Maximum depth of a single-storey rear extension of three metres for an attached house and four metres for a detached house.
• Maximum height of a single-storey rear extension of four metres.
• Maximum depth of a rear extension of more than one storey of three metres including ground floor.
• 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 national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.

Loft conversion guidelines:-

A loft conversion for your home is considered to be permitted development, not requiring an application for planning permission, subject to the following limits and conditions:

• A volume allowance of 40 cubic metres for terraced houses
• A volume allowance of 50 cubic metres for detached and semi-detached houses.
• No extension beyond the plane of the existing roof slope of the principal elevation that fronts the highway.
• No extension to be higher than the highest part of the roof.
• Materials to be similar in appearance to the existing house.
• No verandas, balconies or raised platforms.
• Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
• Roof extensions not to be permitted development in designated areas*.
• Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the eaves.