Town Planning Regulations – including Permitted Development

What are Town Planning Regulations?

Town Planning legislation governs the general principles of building, the external appearance, suitability for the location, effect town planningon neighbours rather than the more detailed considerations such as what insulation or lintel to use – these are largely matters for the Building Regulations. There is often confusion regarding the distinction between the two permissions. Sometimes people incorrectly refer to Town Planning and Building Regulations consents as all encompassing ‘Planning Permission’.


Exemptions to Town Planning Regulations –  Permitted Development (PD)

There are a number of categories of building work that do not require specific consent (often referred to as permitted development) these include:

  • Most internal alterations (although these might often require Building Regulation Approval and listed building consent where applicable),
  • Repair and maintenance type work,
  • Changes to the outside that do not significantly extend beyond the structure
  • Various extensions within certain limits (these in particular can be found at  but a basic guide in for England is given below). Some of the criteria can be difficult to relate to particular circumstances, the rules for example, refer to the ‘principal’ elevation which will generally (but not always) be the front elevation but with some less conventional layouts front, side and rear may be less obvious. In addition it refers to a ‘highway’ which will normally be the road but could also include public footpaths etc. so if in doubt ask your local authority. Some local authorities make a charge for this service or insist that you apply for a ‘certificate of lawfulness’. It means that you have to formally apply for the council to decide whether your proposal requires planning consent. Whilst the procedure has its uses, for example having definite proof consent is not required particularly for perhaps an extension that they may not have approved if a full application had been necessary. Nonetheless it is probably unreasonable to expect someone to have to prepare proper plans and make an application with its inherent delays on the basis of how the council interpret part of the permitted development regulations. A further variation of the ‘certificate of lawfulness’ gives confirmation that the council will not be able to take enforcement action against unauthorised work once beyond the limitation period (generally four years for building work and 10 years for unauthorised changes of use).
  • There are other exemptions not directly related to extensions such as hard standing, satellite dishes etc. further details can be found at The Planning Portal.

General Home Extensions

 This is a general guide to the town planning permitted development criteria for extensions and roof extensions, more specific details can be obtained from or your local authority.


permitted development guideSee under ‘Changes in Permitted Development rules’ for temporary increases to the depth of single storey rear extensions to 8m (detached property) and 6m (others)

Site plan




Original house (or as it was on 1st July 1948)

Single storey rear extension (includes conservatories etc.)

Single storey side extension (not where it would face a road such as on a corner plot)

Multi storey rear extensions, side windows (including in roof) above ground floor level to be obscure glass and not openable below 1.7m to floor level. Height should not exceed original house and roof pitch should generally be the same.

Porch to an external door, a x b =3m² maximum and 3m maximum height.

Detached single storey buildings, not in front of the front wall to the original house.

Building siteplan – the plot of land where the property is built

The combined areas of any extensions should not exceed half the building siteplan (excluding the original house)


  • Materials should match the original house (except conservatories, porches and detached buildings).
  • Eaves should not exceed that of the adjacent original house:
  • Should not include veranda, balcony or raised platform.
  • More restricted limits apply to conservation areas, national parks, areas of outstanding natural beauty etc.
  • Building Regulations and other requirements may still apply.

Roof extensions

roof extension

Site plan


Roof Extensions


Original house (or how it was on 1st July 1948)

Gable end formed from hipped roof (not on front facing road)

Dormer (not on front facing road)

Roof windows

External volume of  the Gabled end formed from hipped roof and Dormer should not exceed 40m³ for a terraced house, 50m³ otherwise.

  • Should not include veranda, balcony or raised platform.
  • Materials should match the existing house
  • Windows (including roof ones) on the sides should be obscure glass and not openable below 1.7m to floor level.
  • More restrictive limits apply to conservation areas, national parks, areas of outstanding natural beauty etc.
  • Building Regulations and other requirements may still apply.

When Permitted Development does not apply

  • Flats, residential accommodation to a shop in fact anything other than ordinary houses or bungalows.
  • When the work creates an additional self-contained dwelling.
  • There are more restricted limits to permitted development to conservation areas, National Parks, The Broads, areas of Outstanding Natural Beauty etc. Demolition within a conservation area will also often require consent
  • Listed Buildings will require Listed Building consent as well for virtually any building work other than minor decorations or maintenance work.
  • Localised restrictions (easily missed) may require Planning Consent. This can sometimes be in the case of a restricted area where the council can apply for an ‘Article 4 direction’ where the normal rights are removed for a defined area. Rather more commonly the original approval (or possibly in some cases a subsequent approval) may put more restrictive conditions on the normal permitted development rights. Typically this might remove all the normal allowances or in some instances just particular ones for example in an area of bungalows it might just remove the rights relating to loft conversions. Although in theory it could apply to any applications made since our present system of town planning legislation started in 1948 in practice it has largely been more prevalent since about 1970’s. It is also more likely to occur in fairly high density properties when uncontrolled extensions could be more of a problem or perhaps properties that have a fairly distinctive character that unsympathetic extensions may have an adverse effect upon. It may be necessary to inspect through former consents to see if these conditions apply, local authorities do not seem to have generally developed systems to readily highlight properties that may be affected.

Changes in Permitted Development rules

Extended depths to single storey rear extensions have been made on a time limited basis (currently running to 30th May 2019) These allow depths up to 8m for detached buildings and 6m for other types however it requires a simplified application to the council (who invite comments from neighbours) and the extension must be completed by the specified date.

An amendment with effect from 6th April 2017 requires a separate check of the more detailed requirements for both the new extension itself  and where it joins an existing extension for the combined extensions

Making a Planning Application

  • If your proposals are not exempt then it will be necessary to make a planning application. In practice for house extensions this is almost always a full planning application known as householder application. There is a procedure for outline applications but this would rarely be suitable in these instances as it would often involve providing almost as much information as a full application but would still require a further application for any aspects not dealt with. Plans are sometimes just drawn initially to the level that is required for a planning application (basically just floor plans, site plans and elevations but not more detailed information on the construction). This might save costs should the scheme not be acceptable, although it does require the designer to be sufficiently experienced to know what is likely to be possible within the Building Regulations in addition being practical to build prior to actually looking at this aspect in detail.
  • The plans are then submitted with the forms (which are standardised between different authorities) and the council fees – there are some exemptions such as work relating to facilities for a disabled person or resubmission of a previous application of a broadly similar nature within 12 months or where an extension would normally be permitted development but this has been removed such as by a previous consent.  Within the more restrictive areas (National Parks etc.) it will be necessary to provide a ‘design and access statement’, essentially a written justification of the proposals.
  • The council will register the application provided it meets with their criteria and will start a process of consultation. In relation to immediate neighbours they are informed directly by post or a sign is put up in the vicinity of the site. Basic details of the application may appear in local papers and parish or town councils will be informed where they exist. More specialist consultations may be made with other bodies such as the highways authorities, Environment Agency (regarding flooding etc.), Natural England (protected species etc.). The planning officer who has been allocated the application will then assess all the consultations, make a site visit and then write a report recommending a decision, a lot of applications are now dealt with under delegated powers which usually means the planning officer together with a senior officer effectively makes the final decision. In some situations though it may be referred to a committee to make the final decision. Some councils allow applicants (and objectors) to address the committee for a few minutes.
  • Although objections from neighbours etc. are not helpful it does not automatically mean an application will be refused, they need to be based on sound planning criteria. Conversely because there is no objection does not automatically mean it will be approved, the planning officers may decide they do not consider it satisfactory.
  • An approval will nearly always have conditions attached; the most usual is that the building work must be commenced within a certain period of time, usually a maximum of 3 years.

Other common conditions

  • Materials to match (or perhaps samples to be provided prior to commencement)
  • No more windows in positions that might cause overlooking or those such windows should be obscured glass. In some situations where the council might consider an extension could be used for a separate dwelling they might put a condition on restricting this although in theory it would require a change  of use application to formally do this.
  • If an application is refused it is initially best to try to discuss it with the planning officer to ascertain what the main problems were and what they might find acceptable. Some planning officers are more helpful than others but usually it is worth trying and if a scheme that is likely to be acceptable to both sides can be agreed a new application can then be submitted.
  • There is generally no additional council planning fee payable for a broadly similar scheme submitted within 12 months. It may however be necessary to pay further professional fees to the designer to change the scheme depending upon any agreement with them as to the extent of their services.


Planning Appeals

When negotiations directly with the council fail to find a mutually acceptable solution it is possible to appeal to the Planning Inspectorate in England.( This has to be done within 12 weeks of the decision although in theory you can appeal against a council for not deciding within the normal 8 week period allowed, although this would rarely be worth doing. It is also possible to appeal against conditions applied to an approval. The chances of winning an appeal vary even to some extent between different authorities, but in general council’s win more appeals than they lose although there is a reasonable chance with a sound case.

There are different methods of conducting an appeal including hearings and inquiries but the majority of home extension cases are dealt with on the basis of written grounds. In this situation a written statement is provided in support of the scheme and the council then provides a statement justifying their original decision. Neighbours and other interested parties cannot normally add to previous comments. An inspector will visit the site and under the written procedure no discussion will take place appeal. The inspector will in due course prepare usually a fairly brief report giving their decision and the reasons for it. This can only be challenged in the High Court and only on a point of law. The overall planning appeal process in theory should be dealt with in 10 weeks for a householder appeal.

It is possible for the layman to conduct their own appeal particularly if the issues are straightforward. Many architects and designers will also conduct appeals. In addition to which there are more specialist town planning consultancies and solicitors who specialise in appeals. There are no actual costs involved in an appeal other than professional fees. Costs can be awarded in exceptional cases under the Hearing and Inquiry procedures if one party is considered to have acted unreasonably.


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