what are Town Planning regulations?

Town Planning legislation governs the general principles of building, the external appearance, suitability for the location, effect on 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’.


Temporary Increase to Permitted Development for rear extensions from 30th May 2013

For a period of three years up until 30th May 2016 rear single storey home extensions not in conservation areas, National Parks, Areas of Outstanding Natural Beauty etc. can be to a maximum depth of 8m (detached dwellinghouse) or 6m for other dwellinghouses. Under revised permitted development rules (SI2015 No. 596) the limits for new extensions has been extended to 30th May 2019.

Other requirements such as eaves height, materials of similar appearance etc. remain the same. Under this temporary increase of Permitted Development it will however be necessary to inform the council if taking advantage of the increased limits. The council in turn will inform neighbours who if they object the council will have to assess the impact of the proposed extension on their amenities and if satisfied give their prior approval. The works can then proceed under these rules if the council either confirm their prior approval is not required, or prior approval is given or 42 days has elapsed from receipt of the original information. Works under these clauses must be completed by 30th May 2016 under the original rules, 30th May 2019 under the revised rules (it is still necessary to keep to the 2016 limit if agreed under the previous criteria) and the council informed as such.

It should be borne in mind these rules do not over-ride other requirements such as previous planning conditions on the site, covenants, building regulations etc.

In addition an extension may come within several categories for example a rear extension that goes beyond a side wall may also have to follow the side extension rules as well as the rear extension rules.

Permitted Development new rules update

Now that the extended limits for rear home extensions have been in existence for a while how are they working in practice?

Have you any experience of the new Permitted Development criteria either as a householder or professional?

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We were always sceptical about how many situations this might apply to, for many properties home extensions of 6 and 8 metres would be excessive and result in very deep or dark rooms and certainly towards the upper limits have been comparatively rare in our experience in the past. Strangely since the advent of the new rules we have had several projects that do come within the new permitted development criteria.

Although one of the reasons it is understood for introducing the 6m and 8m limits was to increase the amount of building work, in most of the cases we have dealt with householders were not aware of the new permitted development rules so their decision to go for a large extension was arrived at independently from this. Some people have been aware of the permitted development changes but often from oversimplified media articles and it turns out that it does not apply in their case (e.g. onto a flat, too high, incorporating a side extension etc.).

In terms of notifying  the council, the amount of information required is very small  (essentially heights and depth) although they can ask for more and as a design practice we would normally supply plans of the extension but for householders one may be able to get away with less before commissioning more detail plans. In theory if the Building Regulations were dealt with under a Building Notice then even this may not be necessary although it could be questionable building perhaps an 8 metre deep extension the width of the house on this basis.

Councils do not charge for processing this type of application which is ironic given that many now charge for pre-application advice and permitted development enquiries etc., although clearly it involves the council in some expense. One of the advantages suggested for the new permitted development rules is the reduction of costs but a saving of £172.00 for the planning fee on a project costing often many tens of thousands of pounds is very small. Significant savings on design fees would only occur in the more extreme cases such as using a Building Notice without plans as mentioned above.

The timescale under this procedure of 42 days is less than most planning applications achieve but it is not sufficient to be that worthwhile by itself.

Although councils are only supposed to be assessing on the amenities of adjoining properties there have been some suggestions that this might occasionally be interpreted rather more widely.

A potential problem for the future is that the householder is supposed to inform the council when the extension has been finished and completion must be by 30th May 2016 under the original criteria although 30th May 2019 would apply to new applications. One can be fairly sure that a number will either not be completed on time for a variety of reasons (lack of finance, problems with builders etc.) or notification will just get forgotten about.  After 4 years it may be possible to obtain a certificate of lawfulness but in the meantime it could potentially mean submitting a retrospective planning application and with a more rigorous assessment may come to a different conclusion. As such within the final year of the rules it will become decreasingly useful unless it is announced in the meantime that they will be made permanent.

If one were being cynical (which of course we are not!) one might think it was more a political gesture to appear to be doing something rather than doing anything that achieved a great deal.


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exemptions to town planning (permitted development)


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),
  • 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 http://www.planningportal.gov.uk/ 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 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.


Local Development Orders

It is possible for local authorities to permit specific types of development within a defined area which could go beyond normal Permitted Development criteria by means of ‘Local Development Order’ (LDO). This could potentially simplify the planning process for developments that fall within a ‘Local Development Order’. Because of the variation of what could be covered by them it is difficult to give further advice, general information on Local Development Orders can be obtained on the Government website, more precise information regarding their existence or what they cover would need to be obtained from the council covering the property in question.

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General Extensions

General Extensions Road

 Temporary increase on rear extensions to 8m and 6m as detailed above

General Extensions - Elevation


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

General extensions

Original HouseOriginal house (or as it was on1st July 1948)

Single Storey Rear ExtensionSingle storey rear extension (includes conservatories etc.)

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

Multi Storey Rear ExtensionMulti 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.

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

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

General Home Extensions

  • 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 ext 3 amended2

Site Plan


Roof Extensions Elevation

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

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

DormerDormer (not on front facing road)

Roof WindowsRoof windows


  • 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.


Permitted Development in Conservation areas, National Parks, areas of outstanding natural beauty, World Heritage Sites, The Broads etc.


There are reduced allowances in these areas in addition to which there is a greater likelihood that other restrictions may apply such as by Article 4 Directions, (additional localised restrictions). The main differences to the general permitted development allowances include:-

  • Although not strictly an extension, cladding the existing building with tiles, render, boarding etc. is not permitted. This is sometimes used as a way of making an extension look more of an integral part of the original building such as rendering both the new and existing parts, but with the requirement to use similar materials on most extensions (except porches and conservatories) it may be more difficult to achieve anywhere if a totally new finishing material is used.
  • Extensions on a side elevation are not permitted, this could include the side walls where the back of the building is staggered as well as the more obvious outer side walls.
  • Rear multiple storey extensions are not permitted
  • Roof extensions (e.g. dormers, hip to gable conversions) are not permitted but other alterations that do not extend by more than 150mm from the plane of the roof are still allowed which would generally include roof lights (still with the proviso that ones on the side are non opening below 1.7m and obscured glass).
  • For detached buildings (not including conservation areas) the total area of buildings etc. more than 20 metres from the house should not exceed 10m², in addition (this time including conservation areas) no building between the side elevation of the house and the boundary.
  • It is generally permitted to install, alter etc. a chimney, flue or soil and vent pipe as long as it does not exceed the highest part of the roof by more than a metre. In the most restricted areas it should not be on the front (principal elevation) or side elevation if it fronts a highway. In addition there are slightly more restrictive rules regarding microwave antenna.(see Class H of SI2015 No. 596 for full details of these requirements).


Permitted Development  - Problems with interpretation

The latest rules applied from October 2008 and brought about a new approach, particularly for the majority of extensions at ground level, and although introducing some new terms was rather short on definitions. Since then the Department for Communities and Local Government (DCLG) has provided some additional informal advice.Initially they answered some anomalies that had come to light followed by a more detailed guidance issued in August 2010.

Some local authorities have also issued their own advice and there have been appeal decisions involving aspects of interpretation. The websites Permitteddevelopment.org and Planning Jungle.com both have further details of planning appeals etc Unfortunately these do not always agree. We have listed some of the common problems that have arisen but as yet these cannot be taken as the definitive answers.


What is a principal elevation?

We have to some extent assumed that generally it will be the front and facing a highway (normally a road but may include a public footpath etc.) which in the majority of cases it is, unfortunately there are still a significant number of situations where it may not be correct. Some have suggested it is generally always the elevation that contains the main door but in practice there are a substantial number of properties with the door on the side where it would not realistically be considered a principal elevation. Some definitions are along the lines of ‘the elevation containing the most architectural detailing’, one can see a certain logic although there will undoubtedly be some exceptions. An elevation that fronts a highway does not necessarily have to be a principal elevation. This has particular consequences for roof alterations because they are only excluded if they are on a principal elevation and front a highway, so would generally be acceptable on a side elevation even if it faces a road (such as corner plot). The rules regarding building in front of the principal elevation also extend either side of the property so a side extension could not be built forward of it.

Can there be more than one principal elevation?

The way it is written is in the singular so answer should be no, the DCLG earlier advice seemed to suggest in some situations there could be more than one but the later guidance says a house will only have one principal elevation. In a situation such as corner plots where two or more elevations may have characteristics of principal elevations it will need to be agreed which is the relevant one.

What are eaves?

The general definition of eaves is the lowest overhanging part of a roof but some councils have interpreted it as being any edge of the roof (such as the upper part of a lean to roof) but some appeal decisions appear to confirm the definition in general use.The current guidance has produced its own definition of eaves height being the height to the top of the roof in line with the outside wall. In the case of a flat roof this would be to the top surface of the roof but not including parapets etc.


Where do you measure depths of extension?

You measure from the base of the original wall to the outer edge of the wall to the extension (not including gutters, fascias etc.) With staggered walls it applies to the wall being built off so the maximum extension would be similarly staggered. 

In the case of a two storey extension on the rear of a detached house the depth has to be a maximum of three metres for both storeys (whether built in one go or one before the other) for it to be considered permitted development i.e. the ground floor part cannot be 4m which would normally be allowed for a single storey building.

With side extensions the maximum width of half the original house is measured at its widest point where it varies.


What are materials of similar appearance?

Both the general category of extensions (excluding conservatories and porches) and roof extensions require external materials to be of a ‘similar appearance’. Whilst in the majority of cases one would tend to try and match there may be cases where this does not occur. Ironically some ‘cutting edge’ architect designs may not conform with this although it is doubtful that restricting these was the purpose of the clause. One of the commonest problems has been flat roofs where they do not occur on the original building, the DCLG has now decided that as flat roof surfaces will not normally have any visual impact the need for materials of similar appearance does not need to apply. Dormers etc. should generally be similar to the roofing materials rather than the main wall materials to reduce their impact.

In general terms colour and style appear to be more important than rigid adherence to the original materials.


What are the problems with side elevations?

Since it only refers to extending to ‘a side elevation’ it could apply to the side elevation of a rear projection such as many Victorian terraced properties, this is a particular problem in conservation areas etc. where side extensions are excluded. With detached properties with room either side of the property it would seem to apply to each side individually (i.e. half the width of the original each side). Extensions which are in front of both sides and rear extension (even if not actually built on them) need to comply with both sets of rules. This can be particularly complicated with wrap around type extensions (where a side extension links with a rear extension), the DCLG guidance gives several examples along these lines.

What of works falling into several categories?

Each individual section generally excludes work falling within another section such as roofs and chimney alterations in relation to general extensions. Some councils have even interpreted it to the extent of excluding an extension because there is an alteration to a soil pipe (which falls into a different category) The DCLG advice would seem to suggest that the works are looked at comprehensively so whilst they may be excluded by one section but allowed by another.

Where is the 200mm set back of dormers measured?

There have been varying interpretations of where the 200mm are measured from - the outer edge of the eaves or inline with the wall below. It has now reverted to the outer edge of the eaves provided that the eaves are maintained and it does not take it beyond the original wall,

Is a ‘juliet’ style balcony considered within the exclusions for balconies?

Apparently not if there is no external access.

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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. 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 have recently become more 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. 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.
  • It may be necessary to provide additional reports such as in flood areas to justify your extension will not be unduly affected (or increase problems to others in the area). In lesser situations it may be sufficient to just ensure that floor levels are no lower than the existing floor levels and materials not unduly affected by damp are used (which might favour brick and block with lime based plasters over materials such as timber frame and plasterboard). You can check if you property is in a flood zone by consulting the interactive Environment Agency Flood map. Other reports that are sometimes required are for protected animal species such as bats, particularly where there are alterations to a roof. A tree report may be required especially if building in close proximity to a tree with a tree preservation order. These reports are often asked for when the application is being registered where there is a known problem.
  • 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 include:

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 extensioncould 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.

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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.(www.planning-inspectorate.gov.uk) This has to be done within 12 weeks (for householder applications) 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 can comment, the applicant and the council can provide further comments on issues raised by other parties. An inspector will visit the site and under the written procedure no discussion will take place other than pointing out features relevant to the 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 usually takes many months.

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 if one party is considered to have acted unreasonably.

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