Extension in Westminster
Do you need planning permission for a single-storey extension in Westminster? Here is what the permitted development rules say, how City of Westminster’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 Westminster?
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 Westminster this matters: the borough has 56 conservation areas and 10 Article 4 directions, 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 Westminster’s designations apply
| Designation in Westminster | Published |
|---|---|
| Conservation areas | 56 |
| Article 4 directions (PD removed) | 10 |
| Listed building outlines | 3,455 |
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 Westminster 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 Westminster 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 Westminster address
A Planning Policy report reads the designations on your exact Westminster address, quotes the City of Westminster and national policies that apply to a single-storey extension, and (on Pro) shows decided applications nearby with outcomes.