Guide
Do I need planning permission for an extension?
A plain-English overview of how the UK planning system treats common home extensions, and the four routes your project might fall under.
The four likely routes
Most householder extensions fall into one of four routes: Permitted Development (often confirmed with a Lawful Development Certificate), Prior Approval, Full Householder Planning Permission, or a case complex enough to need Professional Advice.
Permitted Development
Many small to medium single-storey rear extensions, modest side extensions and certain outbuildings fall within Permitted Development rights, meaning a full planning application is not normally required. Strict size, height and boundary rules apply.
Lawful Development Certificate (LDC)
Where you believe your project is Permitted Development, an LDC gives you written evidence from the council that the works are lawful. It is often valuable when selling the property.
Prior Approval (England)
Larger single-storey rear extensions in England (within set limits) can be built under the Prior Approval “neighbour consultation” scheme. Wales does not currently operate the same scheme.
Full Householder Planning Permission
Where the project exceeds Permitted Development limits, a full householder planning application is normally required.
What can change the answer
- Article 4 Directions removing Permitted Development rights
- Conservation areas, AONBs, National Parks and other designated land
- Listed building status
- Previous extensions on the property
- Flats and maisonettes (different rules apply)
Check your project route
Run the free planning check to see which of the four routes is likely for your project. The result is produced by a deterministic rules engine, not free-text AI.