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Building Plans

In October 2008 the Permitted Development rules changed. A useful website is for advice and to check whether your project requires Planning permission or is Permitted Development. There is a good interactive guide which is helpful.

The following is my summary :

Under Permitted Development, you can build outbuildings with a footprint of up to 50% of the remaining land around the the original house [ as it stood 1.7.48. ]

  • You cannot build in front of the house or side if facing a highway
  • You cannot build higher than the existing roof, including eaves / ridge
  • You can build a 3 metre deep rear extension to an attached house & 4m to a detached house
  • You can build a single-storey extension up to 4m height
  • You can build a first floor rear extension of 3m depth
  • The maximum height within 2m of the boundary is 3m
  • You can build side extensions up to 4m high and up to half original house width
  • Two-storey extensions to be 7m or more from the rear boundary
  • The roof pitches of first floor & two-storey extensions are to match the existing roof
  • The new materials must be similar to the existing house
  • No verandas, balconies or raised platforms
  • Upper floor side facing windows to be obscure glazed with any openings 1.7m above the floor

With roof extensions, the old volume rules apply such as you can increase your roof`s volume by 40 m3 if attached and 50 m3 if detached ; and the beauty of the new rules are you are not penalised, you can have an extension at the same time and not instead of. Now the volumes are irrespective of what other extensions you have or will have. More stringent rules apply to designated areas.

If you require Planning Permission many policies come into play. Size, scale, daylighting, privacy, car parking, form, materials, landscaping incl. trees, amenity and detailing may have an effect. Projects within Green Belt, Conservation Areas and certainly works to Listed Buildings are more difficult to obtain permissions for.

With regards to the Building Regulations, the Approved Documents can be viewed / downloaded here :

With regard to the Party Wall Act 1996 a useful booklet to obtain is :

It is usually worthwhile to contact your Council Planning / Building Control departments for advice OR an agent / architectural practice. The following is some preliminary advice :


Generally requires Planning permission and Building Regulations approval. Site considerations include - size and shape, topography, ground conditions, orientation, trees and vegetation, services, access, existing use and legal constraints. General considerations - Planning policy, Planning history, surrounding area & neighbours.

CONVERSIONS ( Change of Use )

Generally requires Planning permission and Building Regulations. Relevant polices are : impact on area, parking and amenity.


You can extend your property without obtaining Planning permission, under "Permitted Development", subject to these limitations :

  • Terraced House - 50m3 or 10% of the original volume ( maximum 115m3 ),
  • Semi or Detached House - 70m3 or 15% of the original volume ( maximum 115m3 ),
  • cannot cover more than 50% of garden,
  • cannot be closer to a highway than the original house,
  • cannot be higher than 4m,
  • and not in Conservation Areas or to Listed buildings.

Otherwise, you will require Planning permission. To be designed to have no adverse effect on the appearance of the original property, the amenities of the neighbours` or surrounding area.

Note : If "Permitted Development" rights exist, it is prudent to use them for your loft conversion.


The use of your roofspace does not require Planning permission; unless you wish to extend the roof, such as add dormer windows. Under "Permitted Development", dormers are allowed at the rear and side, but not the front ( facing a highway ). Subject to these limitations :

Terraced House - 40m3 maximum,

Semi or Detached House - 50m3 maximum,

If your "Permitted Development" has been used elsewhere, then you will require Planning permission for your roof extensions - which can be difficult to obtain.


You will probably not require Planning permission, but usually you will need to obtain Building Regulations approval.


Under 30m2 floor area and built with safety glazing, does not require Building Regulations approval.


If attached to the house, it is classed as an extension. If detached, more than 5m away, does not cover 50% of the garden, and is not more than 4m high ( pitched roof ), 3m high ( flat ) ; then does not require Planning permission. Single-storey detached building under 30m2 floor area, does not require Building Regulations approval.


Most are within "Permitted Development", except in Conservation Areas and to Listed Buildings.


Within 3m2 plan area externally, not within 2m of a boundary to a public road and maximum 3m high; does not require Planning permission. Does not require Building Regulations approval.


These are the only Council Boroughs where work is undertaken :

London -


Home Counties -


Borough Map

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