Basement extension in Kensington and Chelsea

Yes, and to one of the strictest standards in London. Kensington and Chelsea's Local Plan Policy CL7 and its 2016 Basements SPD require a full planning application for any basement, generally cap excavation at a single storey beneath the house or garden, and limit the basement footprint to no more than 50% of each garden or open part of the site — often less in practice. There is no permitted development route for a basement anywhere in the borough.

Policy CL7 caps excavation at a single storey and no more than 50% of each garden or open part of the site, with a basement impact assessment — among London's strictest.

Basements sit at the intersection of Kensington and Chelsea's two defining constraints — near-total conservation coverage and one of the country's highest concentrations of listed buildings — which is part of why the borough treats basement harm as a standing priority rather than a case-by-case judgement. The economics still support ambitious schemes: this is some of the highest-value property in the country, so a single-storey basement under the house and garden can justify the year-plus programme and specialist cost that basements demand everywhere. But the 50%-of-garden cap in Policy CL7 bites hardest exactly where gardens are already modest, and with such a large share of the borough's stock listed, many schemes carry listed building consent alongside the planning application, with historic fabric assessed as closely as the structural engineering.

There is no useful permitted development route for basements in practice — assume a full planning application everywhere, with a Basement Impact Assessment covering ground conditions, hydrology, structural methodology and construction management. Camden, Westminster and Islington all limit basements to a single storey in most circumstances and protect listed buildings from excavation almost absolutely.

In a conservation area — which blankets much of prime north-west London, from Hampstead to St John's Wood — there is no permitted-development route to lose, but the visible elements are assessed closely on heritage grounds: lightwells, railings, front-garden changes, rooflights and any external alteration. An Article 4 direction or a listed building can remove the option of excavation altogether.

Party wall procedure is heavier than for any other project: underpinning shared walls triggers awards with detailed method statements on both sides, and neighbour objections — on noise, vibration, structural risk and years of disruption — are the norm rather than the exception. The applications that succeed arrive with the engineering done, not promised.