Basement
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in Belsize Park, NW3
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Basement work in Belsize, from refitting an existing lower ground floor to new excavation, planned around Camden's Policy A5, a Basement Impact Assessment and the houses on either side.
Since 1 June 2017 a Camden Article 4 Direction has taken basements out of permitted development, which means any basement or lightwell dug in the borough needs planning permission.
Many Belsize villas already have a lower ground floor. Refurbishing it and digging a new storey are different projects, and we separate them at the first meeting.
Source: Camden Planning Guidance: Basements (January 2021)
Camden's Basement Policy A5
Policy A5 allows a basement only where Camden is satisfied it would not harm neighbouring properties, the structural, ground or water conditions, the area's character, the building's architecture or heritage assets.
The policy caps a basement at a single storey, never beneath an existing basement, covering no more than 50% of each garden and smaller than 1.5 times the footprint of the house above.
Camden counts one storey as about 3 to 4 metres of excavation, measured externally.
Sources: Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021)
The Basement Impact Assessment
The application must include a Basement Impact Assessment, and Camden will usually have it audited independently.
The assessment moves through screening and scoping, then site investigation, then the impact assessment itself, and finally review and a decision.
It has to show that neighbouring buildings face damage no worse than Burland category 1, described as very slight, and it needs a plain-language summary for non-specialists.
Camden says the technical reports should come from a suitably qualified chartered engineer or chartered geologist.
Sources: Camden Council: basement developments, Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017, Camden Council: Basement developments and planning applications
Rising Ground, Clay and Water
The conservation area sits on rising land between Chalk Farm and Hampstead, in a triangle bounded by Haverstock Hill, Adelaide Road and Fitzjohn's Avenue.
Wherever London Clay is not the surface layer, Camden's guidance assumes an aquifer, and it warns that springs can appear where the Claygate Member meets the London Clay.
In flood-prone areas, Camden will not allow a basement to contain habitable rooms or other sensitive uses.
Sources: Camden: Belsize Conservation Area Statement (agreed 20 November 2002), Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017
Lightwells at the Front and the Back
Belsize's statement resists new front basement areas in general, on grounds of traffic and design.
A front lightwell in a shallow garden tends to swallow most of it, Camden notes, and is unlikely to be accepted on a street where lightwells are not already typical.
A side or rear lightwell is often the right way to light a basement and can open onto the garden, set away from the neighbouring boundary.
Where a basement reaches beyond the building's footprint, Camden expects at least a metre of soil above it.
Sources: Camden: Belsize Conservation Area Statement (agreed 20 November 2002), Camden Planning Guidance: Basements (January 2021)
Construction Management and the Neighbours
A Construction Management Plan is a normal requirement for basement schemes in Camden, and is expected in any conservation area or beside a listed building.
GOV.UK's party wall guidance requires notice to neighbours before excavating below and near their foundations.
Skips need a licence, which only the skip firm can request, at least five working days before it is needed.
Sources: Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021), GOV.UK: Party walls and building work, Camden Council: skip licence
Basements in Listed Buildings
In a listed building, a new basement or the extension of an existing one needs listed building consent, whether or not planning permission is required.
Belsize has some 44 grade II listed entries, by the 2002 statement's count, so the list is checked before any basement design.
Sources: Camden Planning Guidance: Basements (January 2021), Camden: Belsize Conservation Area Statement (agreed 20 November 2002)
Basement projects we have completed nearby
Questions about a Belsize Park basement
Does every basement in Belsize need planning permission?
Yes for excavation: Camden's Article 4 Direction removed permitted development for basements in 2017, so every basement or lightwell excavation needs permission.
How deep can a new basement be?
One storey under Policy A5, which Camden reads as about 3 to 4 metres of excavation in total.
Will Camden check the Basement Impact Assessment?
Generally yes; Camden normally commissions an independent audit of it.
Can I dig a lightwell in the front garden?
It is likely to be resisted: the Belsize statement resists new front basement areas, and Camden's guidance says a front lightwell is often unacceptable where it is not part of the street's character.
Is refitting an existing lower ground floor treated like a new basement?
No. New excavation, or deepening an existing level, is basement development under Policy A5 with its own assessment; refitting rooms that are already there is a refurbishment.
Sources: Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017, Camden Council: basement developments, Camden: Belsize Conservation Area Statement (agreed 20 November 2002)
Guides & Local Reading
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Belsize Park history & architecture
Background on the streets, buildings and conservation history of Belsize Park: The Isokon Building · The Water Supply · Belsize House · Belsize Park Gardens · Belsize Village · St Peter’s Belsize Park
Completed renovation project examples
