Home Extensions – how big can it be?

General, Home extension

Anyone who has considered adding an extension to their home will be aware that getting planning permission can be a somewhat drawn out and arduous process. Many homeowners find that they need to wait around 3 months to have their plans approved and that is after they submit the application which can be difficult to understand and requires architects drawings and more. It is understandable, therefore, that people are increasingly looking to avoid the planning process by keeping their extensions small enough to come under permitted development.Home Extensions - how big can it be?

What is permitted development?

Permitted development essentially means that as long as your extension stays within certain size limits (and meets some other restrictions) it can be built with a simple certificate of lawful development. This isn’t essential, but it proves you don’t need planning permission. Your extension is also likely to need to be seen by Building Regulations officers to ensure it meets their criteria – you can find their contact detail with our MyLABC search.

So how big can it be?

Your extension will need to meet restrictions on the placement of the building, the building materials used, the addition of a veranda or balcony and if it is being built in a conservation area or on a listed building. In some cases, planning permission will almost certainly be required. However, when it comes to size, staying within the following limits should ensure you avoid the planning department (note that these all apply to the home as it was originally built).

  • Your extension should not cover more than half the area of land already around your home.
  • The extension should not extend beyond the forward elevation looking towards the road.
  • The extension should not be any higher than the highest part of the roof.
  • A single extension cannot extend more than 3 metres (for an attached house) or 4 metres for a detached house) beyond the rear wall of the original house. In 2019, these limits are increased to 6m and 8m where a neighbourhood consultation has taken place and the local authority has been informed.
  • Maximum height of a single storey extension is 4 metres.
  • Any extension beyond one storey cannot extend further than 3 metres beyond the original wall of the house and the eaves should be no higher than the existing.
  • Side extensions can only be single storey to a maximum of 4 metres and a width no more than half the house.
  • Two storey extensions must not extend further than 7 metres from the current boundary.

There are clearly lots of rules to think about. But your builder should ideally be aware of them and will be able to talk you through what will work best for your property. Don’t forget to contact the council if you are at all unsure, because an extension that has no planning permission may need to be removed.

But with all of these restrictions taken into account, you could have your extension ready in no time.

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