Building an extension is a great way to get more space without the hassle of having to move. If this sounds like the answer to your prayers, it’s worth finding out how big can you build your extension without planning permission. If your project qualifies as a permitted development extension, you may be able to save yourself some time, red tape and fees.
You used to need planning permission to do any work on the exterior of your house, such as renovating the façade, changing windows and doors and building extensions. However, the 2015 Town and Country Planning Order changed all that by providing for some home renovations to be done under Permitted Development Rights (PRDs). Within certain limitations, and provided you don’t abuse them, PRDs work as an automatic grant of planning permission, so you don’t need to apply.
What size you can build your extension without planning permission will depend on the size, location, features and proximity to your boundary. We’ve provided a quick rundown below, but the rules can be complex, so make sure you hire an experienced, reliable construction company or architect that can talk you through everything and help you understand your options.
The main types of extension are either one -or two- storeys built onto the rear of the house, ‘side returns’ built down the side or ‘wraparounds,’ which extend out from the rear and around the side.
Exactly what you can build without planning permission varies for each type of extension. In general, though, you don’t need permission as long as:
Note that the above don’t apply to any home renovations on a listed building or in a conservation area. If this is your case, you’ll always need planning permission.
Also, even if you don’t need planning permission, your extension will need to meet with Building Regulations approval so it can be certified as legal and up to modern fire safety and energy efficiency standards.
If you’re working on walls shared with neighbours, you’ll also need a Party Wall Agreement. If you have sewers on your land, you’ll need a Build Over Permission from the water board.
‘Side returns’ can be built without planning permission as long they are single storey, not more than 4m high and no wider than half the original house.
Single storey extensions to the rear of the house don’t need planning permission provided they don’t extend more than 8m from a detached house or 6m from other types of home. They must also not exceed 4m in height.
You can build a multi-storey extension without planning permission on the back of your house, as long as it doesn’t extend over 3m from the rear wall. The pitch of the roof must also match the existing house, as far as practical, and any upper windows at the side must be obscure-glazed to protect neighbours’ privacy.
A rear extension must not come closer than 7m of your rear boundary. Side returns can be built right up to the boundary as long as the height doesn’t affect neighbours. However, you’ll still need a Party Wall Agreement to build within 3m or dig within 6m of shared boundaries at the side of your property.