Basement
conversions
in Richmond, TW9
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Under a Richmond house the plan allows one basement storey, about 2.7 metres floor to ceiling, and beside a listed building it asks for an independently checked structural impact assessment first.
Front areas, listed neighbours and the Thames
Some Richmond houses already go below ground. Around Richmond Green the Village Planning Guidance lists front basement areas, railings and entrance steps among the townhouses' characteristic features, and on the St Matthias roads it counts open basements among the traits of the Victorian villas.
For a new one, Policy 54 keeps the excavation to a single storey under a home and to half of the garden land, wants at least a metre of free-draining soil above it, and expects natural light and ventilation wherever people will live below ground.
The visible parts are judged closely. Light wells, roof lights and fire escapes must be sited to avoid harm to neighbours, and in a conservation area the plan singles out light wells and railings as the features most likely to affect its character.
Beside a listed house the bar rises: the borough's guidance says basements to listed buildings are rarely acceptable because of the risk to their historic and structural integrity, and the plan asks for a structural impact assessment, with written confirmation that the applicant will pay for it to be checked independently.
Near the river, the plan's basement table refuses any basement in the functional floodplain and requires a new basement to stand structurally independent of the flood defences, or outside their zone of structural influence.
Every basement in the borough needs a Construction Management Plan, which the House Extensions guidance expects to cover access, working hours, parking, deliveries, dust, noise and vibration.
Water is the other constant. The plan notes that basements are vulnerable to groundwater through walls, floors and service entries, and it asks for a pumped sewerage system, as Part H of the Building Regulations recognises, to stop backflow from the public sewer.
Where a light well is needed at the front, the borough's guidance prefers horizontal grilles to railings or upstands, and in a conservation area a new or enlarged light well may not be appropriate at all, depending on how visible the building is.
Next to or under a listed building, Richmond's extensions guidance says a Structural Impact Assessment is always required for a basement, and it asks for mitigation such as non-return valves or a pumped sewage device so that back flows from the sewer cannot flood the new rooms.
Outside Richmond: Fitzjohns Avenue, NW3, a north London house where we built a basement as well as a rear extension.
We map the neighbours' foundations, and note any listed building next door, before an engineer sizes the underpinning, because both decide what the borough will ask to see.
Sources: Richmond: Richmond and Richmond Hill Village Planning Guidance SPD (June 2016); Richmond upon Thames Local Plan 2024 to 2039 (adopted October 2025); Richmond: House Extensions and External Alterations SPD (May 2015).
Basement Conversions in Richmond: Questions
Who checks the structural report for a basement beside a listed Richmond house?
An independent reviewer. The plan requires a structural impact assessment for a basement next to a listed building, with written confirmation that the applicant will pay for the report to be independently assessed.
Can a basement in Richmond be two storeys deep?
Not under a house. Policy 54 resists basements of more than one storey below ground for homes, and it treats as a single storey any space too low to be divided into two floors later, about 2.7 metres high.
Is a basement in Richmond mostly a heritage project?
Often, because so much of the town is protected. Central Richmond, Richmond Green, Richmond Riverside and Richmond Hill each have a conservation area statement, and in a conservation area the plan expects a basement to conserve or enhance its character.
Does the protected Richmond Hill view affect below-ground work?
Rarely the dig itself, but its visible parts can. The Richmond, Petersham and Ham Open Spaces Act of 1902 protects the land on and below the hill for its views west and south, and light wells, railings and garden structures must not harm the setting.
Which Richmond conservation areas apply?
Around the town centre, Central Richmond, Richmond Green and Richmond Riverside, with Richmond Hill to the south; St Matthias covers the plateau and northern scarp of the hill, with high-quality Victorian streets.
What does a basement conversion cost in Richmond?
It depends on the route. Converting space already below ground costs less than excavating a new storey with underpinning, and the reports the plan asks for, such as a screening assessment and a construction management plan, are part of the cost.
Can a listed Georgian house on Richmond Hill take a basement?
Rarely. Richmond's guidance says basements to listed buildings are rarely deemed acceptable, a structural impact assessment and listed building consent are always required, and the plan resists losing original structure and layout.
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