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Permitted Development · Prior Approval · Planning

How big can you build?

Most single-storey rear extensions don't need full planning permission. Many can be built under Permitted Development, and you can often go deeper — up to 6m (semi/terraced) or 8m (detached) — under the Larger Home Extension scheme with a prior-approval application. Here's how the three routes compare.

Standard Permitted DevelopmentNo approval needed

Standard Permitted Development

Up to 4m · detached | Up to 3m · semi & terraced
  • The quickest route — no planning application required
  • Single-storey, rear only, max 4m high (3m eaves within 2m of a boundary)
  • Must not cover more than 50% of the land around the original house
Larger Home Extension (Prior Approval)Prior approval required

Larger Home Extension (Prior Approval)

Up to 8m · detached | Up to 6m · semi & terraced
  • Lets you go roughly twice as deep, still under Permitted Development
  • We submit a Prior Approval application; the council notifies your neighbours
  • 21-day neighbour consultation — if there are no valid objections, you're cleared to build
Full Planning PermissionFull planning permission

Full Planning Permission

Beyond PD limits · two-storey · wrap-around · designated land
  • Needed when you exceed the 6m/8m limits, go two-storey or wrap-around
  • Also required in conservation areas / where an Article 4 direction applies
  • Full design drawings submitted; typically an 8-week decision
Maximum rear depth at a glance

Standard vs. prior-approval depths

PropertyStandard PDWith prior approval
Detached house4 metres8 metres
Semi-detached house3 metres6 metres
Terraced house3 metres6 metres

Depth is measured from the original rear wall of the house (as it stood in 1948, or when first built).

The conditions that always apply

To stay within Permitted Development

  • Single-storey only and to the rear of the original house
  • Maximum height 4m — and no more than 3m at the eaves if within 2m of a boundary
  • No wider than half the width of the original house
  • Extension + outbuildings must not cover more than 50% of the garden
  • Materials similar in appearance to the existing house
The 6m / 8m route, step by step

How prior approval works

01
We apply
We prepare and submit the prior-approval application to your local council on your behalf.
02
Neighbours notified
The council writes to the immediately adjoining neighbours about the proposal.
03
21-day window
Neighbours have 21 days to raise any concerns about loss of light, privacy or amenity.
04
Decision
No valid objections? You're clear to build. If concerns are raised, the council weighs the impact.
When PD usually doesn't apply

The larger 6m/8m allowance is not available on designated land — conservation areas, National Parks, AONBs/National Landscapes and World Heritage Sites — nor on flats, maisonettes or listed buildings, or where an Article 4 direction has removed permitted development rights. In these cases a full planning application is the route.

A friendly note

This page is a plain-English summary to help you plan — it isn't formal planning advice. Every property is different, so we always confirm the right route for your home before any work begins. Our instant quote runs a quick check for you, and you're welcome to ask Daisy (bottom-right) or our team anytime.

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