Do I need planning permission for an extension in London?
The short answer is: check the house, not the internet. Permitted development still exists in London, but on a large share of inner-London streets it has been narrowed or removed. The cost of guessing is a refused application or an enforcement letter.
What “permitted development” actually is
Permitted development (PD) is not a loophole. It is a national grant of planning permission, set out in the Town and Country Planning (General Permitted Development) (England) Order 2015. For houses, the relevant parts sit in Schedule 2, Part 1: Class A for rear and side enlargements, Class B for roof additions, Class C for other roof alterations, Class E for outbuildings.
It only applies to houses. Flats, maisonettes and most houses created through a change of use do not have these rights. Listed buildings need listed building consent even where planning permission is not required. If a previous permission removed PD by condition, the condition wins.
Why so many London houses fail the PD test
Three overlays do most of the work:
- Conservation areas — these are “article 2(3) land”. Class A still allows some rear extensions, but side extensions and cladding are not PD, and Class B roof enlargements (dormers, hip-to-gable, mansards) are not PD at all.
- Article 4 directions — a council can strip specific PD rights from a street or a terrace. Camden uses them widely. Always check the map for the actual address, not the borough in general.
- The existing house — original rear additions, a roof already enlarged, or a terrace that has used its 40m³ roof allowance all eat the remaining envelope.
That is why a 3m rear extension can be PD in one postcode and a full householder application two streets over.
The routes, and what they cost the council in 2026
Fees below are the statutory fee paid to the local planning authority in England from 1 April 2026. They are not our design fee. VAT is not charged on the council fee.
| Route | When it applies | Fee |
|---|---|---|
| Do nothing (true PD) | The works sit inside Class A/B/C/E and no Article 4 or listing applies | £0 |
| Lawful Development Certificate (proposed) | You want written confirmation it is PD — useful on sale | £274 |
| Prior approval — larger home extension | Single-storey rear beyond the PD depth, up to 6m (terrace/semi) or 8m (detached), neighbour consultation | £249 |
| Householder planning application | Anything that needs permission on a single house | £548 |
Listed building consent has no statutory fee. It is a separate application and a separate test.
How we check a London house in the first week
- Property type — house or flat; original dwelling or a conversion.
- Listing, conservation area, and Article 4 on the exact polygon, not a blog map.
- Planning history — previous extensions, conditions, refusals.
- The envelope that is actually left: depth, eaves, ridge, roof volume.
Only then do we draw. A scheme designed as PD and later forced through householder is usually the wrong shape for the officer.
Camden, Islington, Hackney — the local grain
Camden has a high concentration of conservation areas and Article 4 coverage. Assume you need permission until the map says otherwise. Rear additions are judged against the host house remaining dominant.
Islington is short gardens and Georgian/Victorian fabric. Daylight and a subordinate rear eaves line decide more applications than style.
Hackney still has PD on some streets, and a very busy householder caseload on lofts and side-returns. The 2025 Residential Extensions SPD is the document officers will have open.
If you only remember one thing
Do not start on site because a builder said it was PD. If the work is PD, a Lawful Development Certificate is cheap insurance. If it is not, a householder application with drawings that already answer amenity is faster than a refusal plus a year.