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Planning Permission or Permitted Development

Before you can think about building, you must secure an approval from your local authority planning office. For extensions this can come in two forms; planning permission or by using your permitted development rights to obtain a certificate of lawful development.

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What is the difference?

Permitted development rights are a mechanism enshrined within the Town and country planning [general permitted development] [England] Order 2015. Permitted development rights are rights to make certain changes to a building without the need to apply for planning permission and derive from a generalised planning permission granted by Parliament, rather than from permission granted by the local authority planning office.

What this means in practice is that homeowners can extend their homes using the rights but only if the extension complies with the strict criteria set out by the government. Any proposals that do not fit within the criteria would therefore need to obtain planning permission from your local authority planning department.

Permitted development criteria

You are usually within your permitted development rights if you single storey extension or conservatory meets the following –

  • Sits to the side or rear of the house [never the front of the house or otherwise facing a highway].

  • Does not extend beyond the rear wall of the existing house by 3m if attached to others or 4m if detached.

  • Uses similar building materials to the existing house.

  • Takes up less than 50% of the size of the land around the original house. The ‘original’ is deemed the latest of when the property was built or if it was build before 1948, then as it stood on the 1st July 1948.

  • If the side extension is less than 50% of the width of the original house.

  • Is less than 4m in height [or less than 3m if within 2m of a property boundary].

  • Has eaves and ridge that are no taller than the existing house.

There are other rules contained within the government order, and we would recommend getting help from an architect with experience of dealing with this type of planning to ensure that you meet all of the criteria.

If you do plan to using your rights under permitted development to extend, although you do not need one as your rights are enshrined in law, we recommend that you apply for a lawful development certificate. This certificate proves that your design was approved prior to construction and therefore proof that you have complied with the law and your extension is legal. Not only does this give you peace of mind that there is no risk of falling foul of your local authorities enforcement officers, but also means that any future buyers are confident that the work is legal.

The application for a certificate of lawful development is similar to a planning application. Unlike planning applications though there is no chance of a refusal, provided you have adhered to the strict criteria, and there is no opportunity for your neighbours or local politicians to object to your extension.

You will need to provide.

  • The application form

  • Evidence that your proposal meets the strict criteria, including architectural elevations and plans.

  • A site location plan

  • A fee

This process can be managed by yourself, or you can use an architect to act as your planning agent to do so on your behalf. The statutory time limit is 8 weeks, and you should definitely wait for the certificate before starting any work to fully protect yourself.

Are all homes able to be extending using permitted development?

Unfortunately the legislation does not cover all scenarios. Some notable exceptions are:

  • Flats

  • Maisonettes

  • Listed buildings

  • Homes within conservation areas.

If you want to extend any of these properties, you will need to apply for planning permission.

Are all homes able to be extending using permitted development?

If your home is not covered by permitted development or you want to extend beyond the strict criteria, you will need to apply for planning permission.

All requests for planning permission are handled by your local authority and will take a minimum of 8 weeks to be reviewed. You’ll need to provide all the same documents as you would for a lawful development certificate. During the process you will be assigned a planning officer who will deal with your case and review your proposals.

Part of the reason for applications taking 8 weeks to determine is that the planning officer consults with other officers responsible for a range of disciplines within the council, namely drainage, ecology, environmental health, highways and parking, waste, conservation etc etc.

They will also write to your neighbours to consult, allowing three weeks for them to send any objections through.

Decisions are based upon a large number of considerations, including but not limited to;

  • Design and appearance

  • Proposed materials

  • Overlooking/impact on neighbours' privacy

  • Overshadowing/impact on neighbours' access to light

  • Layout

  • Parking

  • Waste disposal

  • Traffic

  • Noise

  • Previous planning decisions

  • Nature conservation

  • Historical significance

  • Layout and density of building

Once your design has been reviewed, you will then be notified of the planning officer’s decision. Your application will either be determined as a simple yes or no, or it could be a yes with a set of conditions that you must include before going ahead with the building.

These are normally things like details of the proposed materials, windows or roofing products you intend to use but can also sometimes require use of additional consultants to provide additional reports on things like archaeology or how the construction will be managed.

It can be a complex process depending on your unique circumstances and we think it worthwhile to employ an architect to manage this process on your behalf. On of the benefits of having an architect as your planning agent is that they can swiftly tweak your plans if the planning officer wants a small change to maximise your chances of getting an approval first time.

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What happens if my planning application is rejected?

This doesn’t mean that you won’t be able to go ahead with an extension at all, nor does it mean that you will have to pay extensive fees to get it overturned.

We recommend taking a pragmatic approach, listening and carefully considering what the reasons for the refusal are before embarking on a course of action.


If you don’t have an architect acting in your corner, you could employ a planning consultant, however you they may advise you that you will need an architect to revise the plans to meet the officers comments. We would recommend taking on board a planning consultant in the event of going to appeal, however you should be warned there is no statutory period for when a planning inspector will review your case. The planning inspectorate report a severe backlog of cases so be prepared for a wait counted in months and not weeks, and they will review the case based on planning policy so it is important that your proposal complies with policy at every step or your refusal could be upheld.

The other route it to re-apply with a revised set of proposals. The re-design should take into account all the reasons provided for refusal by the planning officer and make sure that these are countered. If the re-designed proposals are in essence the same as the original design then this will be a free re-submission to the council, provided it is done within 12 months of your first application. What you want to provide to the planning officer is a set of information that they can tick off against their policies and original reasons for refusal.

If you’ve got any questions about any of the process, please feel free to give us a ring.

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