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Following is a brief explanation of some of the main Planning rules for house extensions, and what is meant by Permitted development ‘PD’.

The most recent legislation came into force on 1st Oct 2008. So long as you keep within the contsraints of these rules you will not need to get planning approval, as it is classed as Permitted development ‘PD’ . Be aware that there are a lot of obscure things written into this act of law. Also note that for any extension, apart from a ‘true’ conservatory, you will need to get BUILDING REGULATION approval (see separate web page)

The first thing that needs to be checked is if there is an Article 4 restriction on development. This is something that was placed on housing developments in and around the 1970’s. It basically means that all extensions need to be submitted for a planning approval. In other words Permitted Development (PD)  has been withdrawn from the house and/or surrounding houses. A planning application must be submitted, but if the extension would have been PD apart from this, the planning fee is not required for the planning submission

The BASIC 3 Metre RULE.

This is one of the Planning ‘permitted development’ rules and will effect most new small extensions, especially conservatory extensions.

These are sometimes built as possibly NOT requiring Planning approval. Care should be taken to assess the situation about the distance of 3m along the boundary.

Without planning permission the council could either make you remove it, or submit a planning application to alter it. This could easily achieve an approval if the walls are ‘splayed’ away from the boundary — see the diagram on the left hand side.

The bottom line is to make sure you are aware of what is allowed – so give us a ring for a bit of free advice.

  • NOTE the confusion is caused by some builders sometimes still thinking as to what was allowed In the OLDER pre 2008 planning rules.
  • A rear extension WAS allowed without planning permission if the property.
  • didn’t have a back street
  • was less than a total of 70 CUBIC metres of extension (all previous extended parts of the house being included.)
  • THESE old rules shown above do NOT now apply.
  • Instead for small extensions and conservatories the following Main rules should be assessed before assuming that an extension can be built without planning permission.
  • you can now ignore the fact that there is a back street or alley at the rear of the property. (the only relevant street or highway is at the front of the property)
  • If the property is a semi detached house, an extension of any kind is allowed rearwards of the main house wall (ie what would be the main 2 storey building), so long as it ONLY projects rearwards 3m in total.
  • If the property is a detached house, an extension of any kind is allowed rearwards of the main house wall (ie what would be say the 2 storey building), so long as it only projects rearwards 4m in total.
  • Total height from ground level to eaves/gutter should be no greater than 3m
  • Total height from ground level to ridge should be no greater than 4m
  • The extension should only be single storey as other rules apply for 2 storey extensions.

Note that the above rules are quite far reaching in terms of conservatory design and it’s requirement for planning permission.

A typical Victorian style conservatory with a 3 metre projection of its side, before the splayed section, is now required to have a planning approval. See sketch at top of this sheet.

NOTE that in almost EVERY case even if an extension doesn’t need a planning approval it WILL need a consent under the Building Regulations. Even to commence work without an approval is liable to attract a hefty fine as the building regulations are an Act of Law, and are frequently updated. Buildings erected which do not comply with these CODES of practice can be issued with a notice to demolish by the local authority.

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