Basement extension in Wandsworth

Yes, always a full planning application — there's no permitted development route for basements anywhere, and Wandsworth applies its own defined standard on top. Local Plan Policy LP6 treats multi-level basements as inappropriate, expects roughly half of both the front and back garden to be retained, and looks for at least a metre of soil above the new basement, with a Basement Impact Assessment and structural method statement expected as standard — and conservation-area front gardens protected even more strictly.

Policy LP6 treats multi-level basements as inappropriate and expects roughly half of both gardens retained, plus a metre of soil above.

Basements are heavily used in Wandsworth, and the borough controls them with a defined numeric standard rather than case-by-case judgement: Policy LP6 and the council's basement guidance set the half-garden and metre-of-soil expectations borough-wide, not only in the protected conservation areas. Inside one of those areas, the same garden-retention expectations tighten further at the front, layered on top of the usual heritage scrutiny of lightwells and railings.

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.