The Complete Loss of Permitted Development in Flats

1. The Misunderstood Law of Flats

The single most dangerous, expensive mistake a property owner can make in the Royal Borough of Kensington and Chelsea is assuming the planning rights of a flat are identical to those of a house. They are not. Flats and maisonettes possess absolutely zero Permitted Development (PD) rights.

Unlike a single-family freehold house—where you can theoretically erect a small rear extension or insert a rooflight without formal planning permission—if your property has been sub-divided into flats, every single external alteration, regardless of how microscopic, requires a full planning application.

2. The Window Replacement Trap

This zero-PD rule catches hundreds of Chelses property buyers out every year. If you buy a drafty first-floor flat and wish to replace the rotting timber windows with identical timber double-glazed units, you cannot simply hire a window fitter. You must submit a full planning application, wait 8 weeks, and pay the council fees. If you proceed without permission, RBKC Enforcement will force you to rip them out.

3. The Freehold Consent Barrier

Even before addressing the council, leaseholders of flats face an insurmountable private legal barrier: the Freeholder. If you intend to execute a Full Refurbishment that alters the external envelope of the building (e.g., adding French doors, a balcony, or an air-conditioning unit), you must secure a formal Licence to Alter from the ultimate owner of the building.

Freeholders in RBKC (often the great Cadogan or Sloane Stanley Estates) have the absolute, unchallengeable right to refuse your request. They frequently weaponize this, demanding exorbitant "premium" payments (effectively a tax on the value you are adding to your flat) before they will sign the Licence to Alter, entirely independent of the council's planning decision.

4. The Complexity of the Basement Flat

If you own the lower-ground floor garden flat and wish to execute a Basement Excavation, the legal complexity is staggering. You are attempting to undermine the foundations of a building containing multiple other owners. Your Architecture team must secure planning permission from RBKC, secure a Licence to Alter from the Freeholder, and successfully serve Party Wall Notices on perhaps six or seven different leaseholders living above you, any one of whom could drag the project into a 6-month legal dispute.

5. Internal Alterations and the Lease

While you do not need planning permission to simply knock down an internal non-load-bearing wall in a flat (unless it is a Listed Building), your lease almost certainly forbids it. The vast majority of Chelsea leases state that the internal walls technically belong to the Freeholder. Proceeding without their formal engineering consent is a breach of lease that can technically result in the forfeiture of your multi-million-pound asset.

How We Can Help

If you are considering a major refurbishment, extension or basement in Kensington & Chelsea, our in-house architectural and construction teams are highly experienced with the specific constraints and policies of the Royal Borough. Do not leave your planning application to chance—our Planning & Permissions and Architecture services are explicitly designed to handle strict London authorities from initial conceptual design through to final, legal consent.

Once permission is secured, our Refurbishment & Interiors division carefully manages the execution, guaranteeing the design integrity is maintained throughout the build phase.

*Published in the Hampstead Renovations Planning Guide Collection — delivering expert design and build strategies for London's most heavily guarded conservation boroughs.*