Basement
conversions
in Fitzrovia, W1T
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Fitzrovia's Georgian townhouses were built with a basement behind a small front area, but where shops were later inserted those areas were often filled in. Camden says excavating under a filled-in frontage would not normally be acceptable.
Fitzrovia straddles the City of Westminster and the boundary with Camden, and the Fitzroy Square Conservation Area protects its finest Georgian streets. Before a basement scheme is even drawn up, the first question is which authority — Westminster or Camden — actually controls the site, since both sets of planning and conservation policy can apply at Fitzrovia's edges.
Fitzroy Square itself is a Robert Adam set-piece of fine Georgian houses; Charlotte Street and Goodge Street mix period townhouses with flats above the restaurants; and Warren Street and its surrounding blocks add mansion flats and conversions — a spread of building types that changes what a basement has to negotiate street by street. Conservation scrutiny stays close throughout, and access on Fitzrovia's narrow streets is tight, so a dig has to plan its central-W1 storage and logistics, terrace structure, mansion-flat acoustics, freeholder approvals and party-wall coordination with close neighbours from the outset.
The cost then depends on the route: converting existing cellar space beneath a Fitzrovia house or excavating and underpinning a wholly new basement, before fit-out is added.
Fitzrovia basements on both sides of Cleveland Street
Camden's 2008 Charlotte Street appraisal describes building that is mostly four storeys, set back from the street behind a small basement area, and an original townhouse form with a basement and sometimes an attic storey. Most lower-floor projects in Fitzrovia therefore improve a basement that is already there.
Where shops were put into the terraces, the railings and basement areas were often removed, the Fitzroy Square appraisal notes. Where that has happened and the pavement now runs up to the building, Camden's Charlotte Street appraisal says excavating the basement would not normally be acceptable.
East of Cleveland Street, Camden resists the loss of original railings and the infilling of basement areas where they are part of the area's character. Its basement Article 4 direction covers the whole borough, so every basement excavation needs planning permission and a Basement Impact Assessment.
West of Cleveland Street the council is Westminster. Its Cleveland Street audit describes plots of two bays and four storeys over basement; its city-wide Article 4 direction has removed permitted development rights for basements since July 2016, and its City Plan treats one storey below the original lowest floor as the most appropriate depth.
Two Westminster conservation areas reach into western Fitzrovia: East Marylebone, first designated in 1982 and extended in 1990 to include the Middlesex Hospital, and Cleveland Street, designated on 20 November 1990. Before a basement is planned there, we confirm which of the two, if either, covers the address.
One related project, though not in Fitzrovia, is Fitzjohns Avenue, NW3, a house in NW3 that gained a new basement and a rear extension. We point to it because the work is comparable; the project itself is outside Fitzrovia.
We confirm which council the address falls in before the survey, because the two councils ask for different documents, and then record the existing basement, its vaults and its drainage.
Sources: Camden Council: Charlotte Street conservation area appraisal and management plan (adopted 24 July 2008); Camden Council: Fitzroy Square conservation area appraisal and management strategy (adopted 16 March 2010); Camden Council: Article 4 directions, other development; Camden Council: basement developments and planning applications; Westminster City Council: Cleveland Street conservation area audit (SPG, adopted 11 April 2006); Westminster City Council: Article 4 directions in Westminster; Westminster City Plan 2019-2040 (2026), adopted 21 January 2026; Westminster City Council: East Marylebone conservation area audit (SPG, adopted 17 March 2006).
Basement Conversions in Fitzrovia: Questions
Which council decides on a Fitzrovia basement?
It depends on which side of Cleveland Street the house stands. Camden's Charlotte Street area runs west to Cleveland Street, the boundary with Westminster; beyond it, Westminster decides. Both councils require planning permission for basement excavation.
Is a basement conversion in Fitzrovia controlled by Westminster or by Camden?
It can be either: Fitzrovia sits across the City of Westminster and the boundary with Camden, and both authorities' planning and conservation controls can apply at the edges of the area, so the first step on any Fitzrovia basement is confirming which one governs the site.
Does the Fitzroy Square Conservation Area limit basement work in Fitzrovia?
The Fitzroy Square Conservation Area protects Fitzrovia's finest Georgian streets, and conservation scrutiny stays close across the district, with access on the narrow surrounding streets tight enough to shape how a basement dig is sequenced.
What drives the budget on a Fitzrovia basement beyond the excavation itself?
Central-W1 access and storage, terrace structure, mansion-flat acoustics, freeholder approvals, facade restraint, services upgrades and party-wall coordination with close neighbours all sit alongside the dig on a Fitzrovia basement job.
Do the Georgian houses around Fitzroy Square need a different basement approach to the flats near Warren Street?
Yes: Fitzroy Square is a Robert Adam set-piece of fine Georgian houses, Charlotte Street and Goodge Street mix period townhouses with flats above restaurants, and Warren Street's surrounding blocks add mansion flats and conversions — each building type changing what a Fitzrovia basement scheme has to negotiate.
Existing cellar or new dig — which costs less for a Fitzrovia basement?
Converting existing cellar space in Fitzrovia and a new excavation with underpinning are each priced after a survey, fit-out not included.
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