Guide

Permitted development rights, explained properly

What you can build without planning permission, what the limits actually are, and the traps that catch people out.

Diagram of a house inside a dashed envelope showing the limits permitted development allows
The box you have to stay inside

The rule nobody explains properly

Permitted development is a national grant of planning permission. It already exists. You do not apply for it, you simply fall inside it or you do not. That is the whole idea, and it is why the question is never "will they let me" but "am I inside the box".

The box, for a house

  • Rear depth. Three metres for a terraced or semi detached house, four for a detached one.
  • The larger scheme. Six and eight metres respectively, but only with prior approval and a neighbour consultation.
  • Height. Four metres maximum for a single storey rear extension. Three metres at the eaves if you are within two metres of a boundary.
  • Roof volume. Forty cubic metres for a terraced house, fifty for a semi or detached. Any previous roof enlargement counts against it.
  • Garden coverage. You cannot cover more than half the land around the original house.

Where the rights disappear entirely

Flats and maisonettes have none. Conservation areas lose roof extensions completely and lose the larger rear extension route. And an Article 4 direction can remove the lot, which is common across inner London and increasingly used elsewhere.

The trap that catches people

"Original house" means as it stood in 1948, or as first built if later. A previous owner's extension eats your allowance. So does a conversion you never knew about. This is the single most common reason a project that looked compliant turns out not to be.

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More guides

Four houses in a row showing a project progressing from bare house to completed extensionGuide

How long does planning permission actually take?

The statutory eight weeks, what really happens, and where the time goes on a householder application.

Read it →Two versions of the same house, one refused scheme in red and one revised scheme approved in greenGuide

Your planning application was refused. What now?

Why householder applications get refused, whether to appeal or resubmit, and how long each route takes.

Read it →A terrace of houses with a dashed boundary running through it, one half inside a designated zoneGuide

Article 4 directions, and why they matter to you

How councils remove permitted development rights, how to find out if yours is affected, and what it changes.

Read it →Two adjoining houses with the shared party wall highlighted and notice zones marked on the groundGuide

Party wall agreements without the jargon

When you need one, what it costs, how long it takes, and what happens if your neighbour objects.

Read it →The same extension drawn twice, once as an outer shell and once cut open to show structure and servicesGuide

Building regulations and planning permission are not the same thing

Two separate approvals, two separate risks. What each one covers and why passing one does not help with the other.

Read it →
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