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Everything you need to know about planning permission for your extension

Planning permission… the bane of everyone’s life when it comes to building an extension. With so many regulations to consider, it can often feel like a complete mission. So, we’ve put together some things that you need to know about planning permission, to make sure you’re prepared for building your extension.

Criteria for needing planning permission

Some extensions will not require planning permission, but it all depends on the size of your proposed extension, the location of it on your property and how many storeys you intend to build. Here are some of the key regulations that mean you will not require additional planning permission:

  1. The size of the extension can’t be any larger than half the size of the existing house – don’t forget to subtract the dimensions of any existing extensions within this too.
  2. If the proposed extension is going to be near a public highway, you will require planning permission, rather than building under the permitted development rules.
  3. Your extension can’t be higher than the highest part of the existing roof. If you want to extend above this, you will require planning permission.
  4. Single-storey extensions for a semi-detached house must not be longer than 3 metres from the initial house, increasing to four metres for a detached house. If your property is more than one storey, the three-metre rule still applies. Anything above this will need planning permission.
  5. If you’re trying to avoid going down the planning permission route for a single-storey rear extension, the maximum height you can get away with is four metres.
  6. Two-storey extensions must be seven metres from the rear boundary. If your proposed extension is due to be closer, you will require planning permission.
  7. Materials used for your extension also need to be taken into consideration. They should fit in with the design of the original house, in order to avoid going through the planning permission process.

Planning permission accepted, what next?

So once you have planning permission granted, you can crack on with your extension, correct? Unfortunately, it isn’t always that simple. You will need to check the title documents associated with your property too, as sometimes consent is required from the original owner or developer. If you miss this stage, you could be in breach of covenant (what can and can’t be carried out on the land). This could mean your extension will have to be taken down at a later date.

There are also building regulations that need to be taken into consideration when building an extension. These regulate things like doors and windows, drainage, electrics, external walls, internal walls, and roofs. Most extensions will require additional approval under the Buildings Regulation Act.

Don’t just take our word for it

The points we’ve highlighted above are not an exhaustive list, so if you’re serious about building an extension we would always advise you to speak with your local planning authority directly as they are experts in the field. Things are always changing too – JSD Group just re-tweeted an article from the BBC, explaining how homeowners in England are free to build bigger extensions.

The team here at KJ Architects are always on hand to help and answer any questions you may have regarding planning permission or extensions – so please contact us today.



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    Studio 2 4 The Highlands Exning Newmarket Suffolk CB8 7NT
    T: 01638 662393
    Everything you need to know about planning permission for your extension