Rear Extensions London — Planning Permission, Size Limits & Costs

Rear Extension Permitted Development Rules (England, 2025)

Single-storey rear extensions can be built without planning permission under Permitted Development rights, subject to size limits:

Terraced and semi-detached houses: up to 3m depth from the original rear wall.

Detached houses: up to 4m depth.

Under the Neighbour Consultation Scheme (Prior Approval): Extended limits apply — up to 6m for semi/terraced, up to 8m for detached houses — but you must apply for Prior Approval and neighbours have 21 days to object.

Maximum height: 4m at the highest point, and no higher than the eaves of the existing house.

What is NOT Permitted Development

Your extension requires full planning permission (regardless of size) if:

- Your property is a flat or maisonette - Your property is in a Conservation Area - The extension would cover more than 50% of your garden - Your council has issued an Article 4 Direction removing PD rights - Your property is Listed

In London, many boroughs have removed PD rights via Article 4 Directions for terraced properties. Always check before assuming Permitted Development applies.

Double-Storey Rear Extensions

Double-storey extensions have much tighter PD limits: maximum 3m depth, must be set back 7m from the rear boundary, and cannot be within 2m of the plot boundary. In practice, most double-storey rear extensions require full planning permission.

The Neighbour Consultation Scheme

For single-storey extensions between 3–6m (semi/terraced) or 4–8m (detached), you must apply for Prior Approval from your local council. The council notifies your neighbours, who have 21 days to object. If they do not object, or their objections are not upheld, you can proceed.

SuperBuilder can submit Prior Approval and full planning applications on your behalf through our approved planning consultants. Call 0800 530 0853 for advice specific to your property.