Planning Permission for Your House Extension

Building an extension on your home is a great way to provide your family with the space you need, and add value to your home. Provided you do everything right you can get an amazing return on your investment.

Why build an extension

One of the main reasons for building an extension is to add value to your home. How much value depends on several factors. This includes where you live, the value of housing in your area and the type of extension you have built. For example, according to recently released data from Countrywide PLC adding a 30-metre extension to a house in Winchester that is worth £249,000 would generate an ROI of £61,000. Do the same to a house in Cambridge with a value of £245,000 and your ROI is just £57,000.

Despite the variance in ROI, it is very clear that, for most homeowners, adding an extension makes a lot of sense. However, it has to be well constructed and be built legally.


The importance of the right planning permission

If the extension or conservatory you build is poorly constructed you can end up reducing the value of your property. Building an extension without the proper planning permissions could even make your home unsalable.

Naturally, the improvements you have made to your property will make your home more attractive on paper. For example, if you have added an extra bedroom, your house is likely to be far easier to market.

In all likelihood, a lot of prospective buyers will come round to see your property. Usually, someone will put an offer in, and you will think that you have sold your house.

However, the moment the solicitor does the legal searches, he or she will discover that your lovely extension is not legal. When that happens, your buyer is highly likely to withdraw their offer.

This is because getting an illegally built extension legalised is not easy. It can take a long time to do, and it can be very expensive.

In addition, there is a risk that the extension cannot be legalised. In which case, it would need to be demolished.

As you can imagine few buyers are willing to take that risk. Even if they are still interested in buying your house, they are likely to want a huge discount.

Getting a mortgage on an illegally extended property can be very difficult. Therefore, even if you find someone who is willing to take on the problem it could be impossible for them to borrow the money they need to buy your house. Therefore, the sale could still fall through.

It really is not worth taking the risk of building without the proper permissions. Some people will tell you the authorities do not check private homes. In reality, they do, admittedly not often, but it happens and, when they discover planning abuses, they act.

In addition, every year neighbours report hundreds of planning abuses to the authorities. Add in the fact that the illegal work will be discovered when you or your children try to sell the property and you can see it really is not worth taking the risk of building without the proper permissions. A far better approach is to make sure that the extension you want to build does not require planning permission.


Follow our guide to building an extension

In this article, we cover the rules that apply to properties located in England. It is important to note that Wales, Scotland and Northern Ireland each have their own sets of regulations.

They are broadly similar to those outlined below, but there are differences. Therefore, you need to refer to the latest regulations for the country your property is located in.

We also need to highlight the fact the information in this article is correct at the time of writing. Planning regulations can, and do change, on a regular basis. Therefore, please look upon the information outlined below as guidance. Before you start planning your extension, be sure to double check the latest set of rules for your area. You can do so online, or by checking with a local architect. Give us a call if you’re not sure – we’d be happy to advise.

Given the fact your extension could be torn down if it is built illegally it really does make sense to be careful. Our advice is to double check everything before building anything.

Do you actually need planning permission?

If you want to build a new property, no matter how small, you need to seek full planning permission. This is the case wherever you live in the UK. However, many home extensions and conservatories do not need planning permission.

This is because of something called ‘permitted development’. If the changes you are planning fall into this category, you do not have to seek planning permission.


What is permitted development?

You can find details of the government’s latest ‘permitted development’ regulations on their planning portal website. These rules change on a regular basis, so you should always go there to check for the latest information before starting work. However, below we have summarised the most important criteria for you.

Single-storey rear extensions

Normally, if you are building a single storey extension or conservatory on the rear of your semi-detached property that does not extend more than 3 metres from the original building you do not need planning permission. For a detached property, the limit is 4 metres.

It is important to note the use of the term ‘original building’ rather than ‘existing building’. If a previous owner has already extended your property by a metre, the most you can add without planning permission is two metres. You cannot simply add three more metres to your existing property.

Temporary rule for rear single-storey extensions

For extensions where construction will be finished prior to the 30th May 2019, the permitted build limits have been doubled to 6 and 8 metre respectively. This is part of a government scheme which has been set up to stimulate the construction sector and increase the housing stock.

However, you actually do need to notify the authorities of these bigger extensions. This is so that they can formally notify your neighbours of the changes you plan to make and give them a chance to highlight any concerns they have. See the section below entitled ‘the neighbour consultation scheme’ for more details. If objections are raised by surrounding property owners there is a chance that you will not be allowed to build your bigger extension.

If you are building a single storey extension onto a bungalow, the height of the eaves and ridge cannot exceed that of the original house. The pitch of the roof should also be similar.

In addition, the finished extension cannot be higher than 4 metres. However, if the extension is within two metres of your property boundary the eaves cannot he higher than three metres.

Most garages, sheds and outbuildings do not require planning permission.

Double storey rear extensions

Potentially, you can also build a double storey extension that extends up to 3 metres beyond the footprint of the original house. For this reason, if you are planning to build a two-storey extension you need to check that a previous owner has not built onto to your house before you bought it.

You also need permission if you want to build a double storey extension closer than seven metres from the rear boundary of your property. This is regardless of how big the extension is. Even if you just want to add a metre or two you will need full planning permission because of the impact it could have on your neighbours.

For double storey extensions, the roof pitch must match that of the existing house. The eaves and ridge height of the extension must not exceed that of the original house.

Any side facing windows located on the upper floor of your extension have to be obscure glazed. Level four or five obscuring glass has to be used for this task.

Those windows can have the ability to be opened, however, the opening has to be at least 1.7 metres from the floor of the room in which it is installed. These two standards are there to protect the privacy of your neighbours, so they are strictly enforced.

You cannot include a balcony or raised platform as part of your extension. It may be possible to do if you seek planning permission.

In some areas, double storey rear extensions are not permitted. Your local council should be able to confirm whether you live on this category of land.


Side extensions

If you plan to build an extension on the side of your home, without seeking planning permission, it has to be a single storey with a maximum height of four metres.

The width cannot be more than half that of the original house. That is the size of the property when it was first built. If a former owner already extended the property, you may not be able to extend it further without seeking full planning permission.

In some areas, no side extensions are allowed. Your local council can usually confirm whether this is the case.

The land your extension takes up

Regardless, of the type of extension you build the finished extension must not take up more than 50% of the original land around the house.

Building material limitations

The materials used for your extension have to be similar to those used in the existing house. This is the case for any type of extension regardless of how close it will be built to your property boundary. In some areas, you are not allowed to clad the exterior of your property, which reduces the range of finishes you can choose.

Proximity to a highway

If your property is next to a highway, there are additional restrictions to consider. For example, you cannot build an extension that sticks out further than an existing building towards a highway.

Land regulations

For some plots, there are further, land related, restrictions in place. They vary, but, as we mentioned earlier, some properties cannot have side extensions, whilst others cannot extend from the rear of the property.

In addition, restrictions may apply if you live in an area of scientific interest, areas of ‘Outstanding Natural Beauty’ or a conservation area. Further restrictions apply in National Parks, World Heritage Sites or on The Broads

If your property is listed further restrictions may apply. These mostly relate to the materials used.


Other considerations

Even if your planned extension meets the latest ‘permitted development’ criteria, outlined above, that does not mean that you can start digging the footings straight away.

Building an extension legally is not just about planning permission. There are other regulations that affect what you can build.

The neighbour consultation scheme

If you decide to build a large single storey extension, you still need to notify the local authorities of your intention to build. When you do so, you need to provide a written description of the proposed extension.

It must state how far the new building extends from the existing home, the height of the eaves and the highest point of the extension. There must be a plan of the site showing the size of the plot, the house and the proposed extension. The contact details for the developer, as well as the addresses of all adjoining properties also need to be included. Once the local authority has those details, they will notify the neighbouring properties of your plans to extend.

This gives them the opportunity to log any objections they have about what you plan to do. Your neighbours have 21 days from the day they receive the notice to lodge any concerns.

The local authority will then decide whether your extension can go ahead and notify the developer within 42 days if they are happy for you to build as planned. If you do not hear from the authorities by then, it means you cannot build your planned extension. However, your developer can appeal that decision. If you win your appeal, you may be able to go ahead, and build.


Building regulations

In addition, your extension has to comply with all building regulations. This fact can restrict what you can build.

For example, you may have space for a new downstairs toilet, but not enough room to put in the legally required drainage. Therefore, building regulations are also an important consideration when planning an extension.

The best approach

As you can see there is a lot to consider when building an extension. Making sure that everything is covered, and getting it right is not easy.

Therefore, it really makes sense to invest in having your ideas looked at by an architect. They will soon tell you if you need to notify the authorities of your plans to extend. If you need to do so, they will help you to pull together the necessary documentation.

Should it turn out that your extension does need full planning permission they can sort that out for you. They will draw up the plans and make sure they are submitted correctly.

If you have any questions or concerns about an extension you are planning, please give us a call or email us on – we’d love to hear from you.

Posted by Matt Hughes
February 5, 2016

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