Flats and leasehold: why you have no permitted development rights

Most planning advice online quietly assumes you own a house. If you own a flat, much of it simply doesn't apply to you. Permitted development — the automatic right to extend, add a dormer, build an outbuilding or change windows without a planning application — is granted to dwellinghouses, and in planning law a dwellinghouse explicitly does not include a flat or a building containing flats. The practical result is stark: a flat has no permitted development rights, so almost any external alteration needs a full planning application.

London is overwhelmingly a city of flats — converted Victorian houses, mansion blocks, ex-local-authority maisonettes, new-build apartments. If you're one of the millions of Londoners who owns a leasehold flat, this page explains what that means for any work you're planning: the consents you need, the order they come in, and the traps — amalgamation chief among them — that catch leaseholders out.

Why flats are excluded from permitted development

Permitted development rights come from the General Permitted Development Order. Its definition of "dwellinghouse" — the thing those rights attach to — specifically excludes a building containing one or more flats, and a flat contained within such a building. So the rights to extend, convert a loft, add a porch or build a garden room, which a house enjoys automatically, do not exist for a flat. There is no permitted-development shortcut to lose; there was never one to begin with.

The triple-consent reality

Where a house owner deals with one consent regime (planning, and only sometimes), a flat owner can face three independent ones for the same piece of work. They are separate, and having one is not evidence you'll get the others:

• Planning permission — from the council, for external alterations and changes of use. Required for a flat where it often wouldn't be for a house, because there's no permitted development to fall back on.
• Listed building consent — from the council, if the building is listed, for works affecting its character, inside and out. Many London mansion blocks and converted period houses are listed. See our listed building consent guide.
• Licence to alter — from your freeholder, under your lease, for structural and many non-structural alterations. This is a private contractual consent, nothing to do with the council, and your lease almost always requires it. See our licence to alter guide.

Internal works: planning usually no, the lease usually yes

Internal alterations to a flat — moving a non-structural partition, refitting a kitchen or bathroom — generally don't engage planning permission at all, because planning controls external appearance and use, not your interior layout (the listed-building exception aside). But the lease is a different matter: most leases require the freeholder's consent for structural alterations, changes to services, and often any alteration at all. Building regulations still apply to the construction. So the typical internal flat project needs no planning permission, but does need a licence to alter and building control sign-off.

The amalgamation trap

Combining two flats into one — or splitting one into two — is not just an internal job. Changing the number of dwellings is a material change that needs planning permission, and several central London boroughs actively resist it. Westminster and Kensington & Chelsea, in particular, have policies protecting the existing supply of homes and resisting the amalgamation of smaller units into larger ones. Owners of adjoining flats who assume knocking through is a private matter between them and the freeholder can find the council refuses the change of use outright. If amalgamation is your plan, check the borough's policy before you buy the second flat.

Ground-floor flats and gardens

A ground-floor flat with a garden is the one case where extension is sometimes feasible — but it's still a full planning application (no permitted development), and it still needs the freeholder's consent, which often turns on whether the lease even grants you the garden. The planning route is the same as a house in design terms — scale, neighbour amenity, the 45-degree daylight test — but with none of the permitted-development fallback and an extra layer of freeholder consent on top.

How this connects to your Planning Permission Checker report

The Planning Permission Checker area report tells you whether the building is listed and whether it sits in a conservation area or Article 4 area — the planning designations that frame any flat alteration. What it can't see is your lease, which is where the licence-to-alter requirement lives. For leasehold flats, especially listed ones or amalgamations, enquiries route to Hampstead Chartered Surveyors, an RICS-regulated practice (Firm Reg. 923064) that advises on the planning, listed-building and licence-to-alter layers together.