Do You Need Planning Permission for a House Extension?

One of the first questions we get asked at the initial consultation stage is whether an extension will need planning permission. The honest answer is: it depends. Some extensions can be built under what is known as Permitted Development, without a formal planning application. Others need full planning permission before a single brick is laid. Getting this wrong, or assuming the wrong answer, can delay a project by months.

What is Permitted Development?

Permitted Development rights allow homeowners to make certain changes to their property without submitting a full planning application. These rights are set nationally, but they come with limits on size, height and position that vary depending on your specific property and location.

A typical single storey rear extension, for example, may fall under Permitted Development if it stays within set size limits and does not extend beyond a certain distance from the original rear wall of the house. Once those limits are exceeded, or if the property sits in a conservation area, the same extension is likely to need full planning permission instead.

When full planning permission is usually required

A few common situations that typically call for a full planning application:

• Extensions that exceed the size and height limits set for Permitted Development
• Properties in conservation areas, such as parts of Canford Cliffs
• Listed buildings, or properties within their curtilage
• Flats and maisonettes, which do not carry the same Permitted Development rights as houses
• Extensions that would significantly reduce garden space or affect a neighbouring property

It is also worth remembering that Permitted Development rights can be removed entirely on some properties, often through what is called an Article 4 direction. This is more common on newer developments and in certain conservation areas, so it is always worth checking before assuming a project qualifies.

Building Regulations apply either way

Whether or not planning permission is needed, Building Regulations approval almost always is. This covers the structural, fire safety and energy efficiency standards a build must meet, and it is a separate process from planning permission itself. A well managed project accounts for both from the outset, rather than treating Building Regulations as an afterthought once planning has been granted.

How we handle this for our clients

Our in-house design team reviews the planning position for every project as part of the initial consultation and design stage, before a detailed proposal is put together. Where a full application is needed, we manage that process directly with the local planning authority, drawing on experience across Poole, Bournemouth, Christchurch and the wider Dorset area. You can read more about how this fits into the wider build on our House Extensions page.