Extension in London
Do you need planning permission for a single-storey extension in London? Here is what the permitted development rules say, how City of London Corporation’s designations change them, and what decides an application, grounded in the official guidance and quoted verbatim.
Do you need planning permission for a single-storey extension in London?
Many single-storey rear extensions are permitted development under Class A, within set limits on depth, height and how much of the garden they cover, so no planning application is needed. In London this matters: the borough has 28 conservation areas, and inside those the permitted development route narrows or is removed, so a single-storey extension can need a full application where it would not two streets away.
The starting point
Many single-storey rear extensions are permitted development under Class A, within set limits on depth, height and how much of the garden they cover, so no planning application is needed.
“This provides permitted development rights for the enlargement, improvement or other alteration of a house.”PD technical guidance, Class A · full text in the library → · official source →
How London’s designations apply
| Designation in London | Published |
|---|---|
| Conservation areas | 28 |
| Article 4 directions (PD removed) | 0 |
| Listed building outlines | 636 |
Because extension depends on permitted development rights restricted on article 2(3) land, the conservation areas above are decisive: inside one, expect to need a full application. Counts are read live from planning.data.gov.uk; your report checks them against your exact address.
What London weighs
Where an application is needed, design does the deciding: depth against the neighbouring rear walls, loss of light, roof form, and materials against the parent building.
As a London borough, City of London Corporation also decides against the London Plan 2021 (the strategic policy layer for all 33 boroughs), alongside national policy and its own Local Plan.
See a single-storey extension in a real report
London’s most common project: a kitchen extension behind a Victorian terrace in a conservation area with an Article 4 direction. 262 nearby decisions, 81% approved.
Get a planning report for your London address
A Planning Policy report reads the designations on your exact London address, quotes the City of London Corporation and national policies that apply to a single-storey extension, and (on Pro) shows decided applications nearby with outcomes.