Do You Need Planning Permission for a Rear Extension?

In most cases, no. Single-storey rear extensions on houses (not flats) fall under Permitted Development rights up to certain size limits — meaning you can build without submitting a planning application at all. The limits depend on whether your house is detached, semi-detached, or terraced.

The size limits that matter

Under standard Permitted Development rights, a single-storey rear extension can extend:

Height matters too: the extension can't exceed 4m at its highest point, and if it's within 2m of a boundary, the eaves height can't exceed 3m.

The Neighbour Consultation Scheme — going bigger without planning permission

If you want to go larger than the standard limits — up to 6m for a semi/terrace or 8m for a detached house — you can use the Neighbour Consultation Scheme (sometimes called "prior approval"). This isn't a full planning application, but your council does notify adjoining neighbours, who have 21 days to object. If no one objects, you're clear to build without a formal application.

When you definitely need planning permission

You'll need a full application if:

• The extension would go over the size limits above, even with the Neighbour Consultation Scheme
• Your house is in a conservation area or is a listed building
• You've already used up your Permitted Development allowance with a previous extension
• It's a double-storey extension going beyond the rear wall by more than 3m, or exceeding certain height/proximity rules to boundaries
• Your property is a flat or maisonette — Permitted Development rights for extensions generally don't apply to flats

What about building regulations?

This is separate from planning permission and applies regardless of whether you needed planning permission or not. Building regulations cover structural safety, fire safety, insulation, and drainage. Every extension we build is signed off against current building regulations, and we handle the building control applications as part of the project.

Our honest advice

Don't assume — check. The rules above are the general position, but every property is slightly different (previous extensions, Article 4 directions removing PD rights in some areas, listed building status). At your free site visit, we check your specific situation against current planning rules before you commit to anything, and if a formal application is needed, we handle the submission and drawings.

See our full house extensions service or read our guide on Permitted Development rights explained for the broader picture beyond just extensions.