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Planning Permission for Extensions

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  • 09-09-2020
Planning Permission for Extensions

What Are The Rules on Extensions to Houses?


What Size Extension can I Build Without Planning Permission?

Recently the permitted development rules have been relaxed, and this means that you can build an extension of up to six metres without planning permission.

If your house is detached, you are now permitted to build up to eight meters. An extension or addition to your home is usually considered to be permitted building development.

Therefore, you will not need to go through the additional process of getting planning permission as long as: The extension you are building is no more than half the area of land around the original house. 

The term "original house" is seen as it was in 1948, or after this date how it was newly built. Extensions of more than one storey are not permitted to extend beyond the rear wall of the original house by more than three metres.

Anything more than the allowed three metres, and you would require planning permission for your extension.The maximum eaves and ridge height of your extension must be no higher than the existing house.

Although you might not need planning permission, you will likely need approval under the Building Regulations. There are some classes of new buildings or extensions of existing buildings that do not require Building Regulations approval, i.e. are exempt from the Regulations. Your local planning office will give you advice on what planning permission or building regulations are needed. It is always best to find this out before you start any work on your property. 

How much does Planning Permission for an Extension Cost?

For any project where planning permission is required, be it a conversion, extension or new build the process will involve fees paid to the council. Planning fees fall into three sections.

There are the rates for statutory planning applications, then council charges, including pre-app costs, the Community Infrastructure Levy. (CIL) and other payment demands, and finally, professional estimates.

The first of these costs is the most certain, prices are set nationally, so are the same throughout the whole of the United Kingdom. Self-builds are exempt from the Community Infrastructure Levy. (CIL), so if your building project qualifies then you won't need to pay this.

Other council expenses can vary and can be considerably costly for things like for pre-app or legal agreements. Likewise, professional fees can increase your budget, especially if you require several different professionals for your project.

Applying for full or detailed planning permission for a house conversion or new house in England is at present £462.00. For outline applications, it is £462.00 per 0.1 hectares. Householder applications, needed for garden buildings or extensions are £206.00.

Suppose your planning permission is granted as it often is, subject to any conditions. In that instance, a request to approve any details that were asked for, i.e. landscaping or materials details is £116.00, while householder applications are £34.00.

You can, of course, cover multiple conditions under a single request. Still, if you want to submit the documents online via the Planning Portal, there is an additional £20 processing charge. 

What are the Rules for Extensions?

The extension project has got to be single-storey only, the finish should resemble your existing property, and the extension cannot be more than half the width of the original property.

You must be aware that restrictions on height apply, depending on how close you will be building to the Boundary of your property.

Can I Extend my Conservatory without Planning Permission?

A conservatory and an extension fall under the same rules and are considered permitted developments, so they don't require planning permission; this is, of course, subject to any limitations.

You will require planning permission for a conservatory if: More than 50% of the land around the 'original house' is to be covered and this will include any other buildings. The term "original house" is seen as it was in 1948, or after this date how it was newly built.

Do I need Building Regulations for a Small Extension?

In the majority of cases, most property extensions will require approval under the Building Regulations. There are several classes of extensions of existing buildings or entirely new structures that do not need approval by Building Regulations.

In these cases, it means they are exempt from Building Regulations. However, even if the building is exempt from the regulations, the work may still require planning permission, this is something that is checked before any work commences. 

How Close to my Boundary can I Build an Extension?

There are two different types of Boundary in English and Welsh property law. They are the legal Boundary and the physical Boundary.

The legal Boundary is a line on the plans or a description of the area in which divides your property from your neighbour. The physical Boundary is any barrier or object that separates your property from your neighbours, such as a wall, hedge or fence.

It can be difficult to understand the regulations and rules when it comes to extensions and boundaries. If you are planning to build any extension that is more than one story, you are then restricted to no more than 3m beyond your rear Boundary, this, of course, will only apply if there are no buildings on the land at the rear of your property.

Can my Neighbour stop me Building an Extension?

There was a scheme that was due to run out end of May 2019 it is called the Neighbour Consultation Scheme; this scheme has now been made permanent. It makes it possible to double the amount you can extend your project.

Can my Neighbour Build an Extension on the Boundary Line?

The answer is yes they can, subject to them serving a valid notice and following the processes and procedures set out in The Party Wall Act. Boundary walls are referred to in the Act as "Party Fence Walls".

The definition set out for a party fence wall is: "a wall that is not part of the building which stands on the land of different owners and is either constructed to be used or is used for the separation of the adjoining grounds.

The party wall act only applies to any structures with a foundation like a wall with a foundation it does not apply to timber fences or other types of screens.

What is the Neighbour Consultation Scheme / Larger Home Extension Scheme?

The Neighbour Consultation Scheme or Larger Home Extension Scheme will allow homeowners to build single-storey extensions to either: A semi-detached house or a terraced house can be extended up to 6 metres and a detached house up to 8 metres from the original house.

However, your neighbours do have the right to object to your home extension. Your neighbours have a 21 day period in which they can give valid reasons as to why they believe the extension should be given permission or allowed to be constructed.

Your local authority then has a further 21 days to grant this prior approval.There are no fees for a Prior Notification application. However, once the statutory 42 day period is over, a fee is then payable for a lawful development certificate, which then takes eight weeks to receive a decision.

Should my neighbours accept my home extension build?

If I have had my Planning Permission granted or my extension falls under permitted development, does that mean my neighbours must accept my home extension build?

There is a chance there could still be an issue with a Party Wall Agreement, or it might be that unfortunately, you have a neighbour that is just trying to be extremely difficult.

If your neighbour is inclined to do so, they could take legal action against the local council for their Planning Permission decision; this can be time-consuming and stressful, although it is infrequent for this to happen. 


If you want to find out more information about whether you need planning permission for your building project, you can discuss it with your local architect. If you are looking for an architect in London we can help you with planning permission advice.