Basement
conversions
in West Hampstead, NW6
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Surface water and shallow Victorian foundations make West Hampstead a place to dig with care, as the neighbourhood plan itself warns.
The neighbourhood plan's basement concerns cover the stability of adjoining houses, the loss of gardens and their wildlife, sustainable drainage and carbon emissions.
We start every basement enquiry with the ground: a desk study, the drainage records and, if the scheme goes ahead, boreholes.
Source: Fortune Green and West Hampstead Neighbourhood Plan (adopted by Camden, September 2015)
Surface water and flooding
Camden guidance cited in the plan identifies West Hampstead, South Hampstead and Cricklewood as subject to localised surface water flooding, and many streets in the area have flooded in the past.
Camden does not permit habitable rooms or other sensitive uses in basements in areas prone to flooding.
So a West Hampstead basement is designed with its drainage, pumps and any flood barrier as central parts of the scheme, not extras.
Sources: Fortune Green and West Hampstead Neighbourhood Plan (adopted by Camden, September 2015), Camden Local Plan 2017
One storey, and caution below it
The plan accepts that some sites may take a one-storey basement, since many houses were built with cellars, but urges more caution deeper down because many have shallow foundations.
Camden's Policy A5 likewise keeps a basement to one storey and to no more than half of any garden.
Where a house already has a cellar, enlarging and waterproofing it is often the first option we price.
Sources: Fortune Green and West Hampstead Neighbourhood Plan (adopted by Camden, September 2015), Camden Local Plan 2017
Lightwells and gardens
In South Hampstead, Camden found many basement schemes with front and rear lightwells, some so large that they took much of the garden.
Long, undeveloped rear gardens are central to that conservation area, and schemes that do not respect them will be resisted.
We keep lightwells as small as the rooms allow and place them where they are least seen from the street.
Source: Camden: South Hampstead Conservation Area Character Appraisal and Management Strategy (February 2011)
Camden's tests for a basement
Policy A5 asks the council to be satisfied that a basement will not harm neighbouring buildings, ground and water conditions, the character of the area or heritage assets.
The Basement Impact Assessment must keep predicted damage to neighbours within Burland category 1, very slight.
Every basement or lightwell dig in Camden has needed planning permission since an Article 4 Direction took effect in June 2017.
Sources: Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021)
Preparing the impact assessment
Camden's assessment runs from screening and scoping through site investigation to an impact study and review.
It must open with a plain-language summary for readers without technical training.
A chartered engineer or chartered geologist belonging to the relevant institution should author the technical reports.
Sources: Camden Planning Guidance: Basements (January 2021), Camden Council: Basement developments and planning applications
Converting an existing cellar
Many West Hampstead houses have a cellar under the front rooms, reached by steps from the hall. Lowering its floor and lining it can give a utility room, a study or storage without a new basement under the garden.
The work still needs care: underpinning the walls if the floor goes below their foundations, a drained membrane against damp, and ventilation and a second way out if the room is to be lived in.
We survey the cellar first and price this option before any larger basement is considered.
Neighbours, notices and construction
Party Wall Act notices go to neighbours whose foundations the dig comes below and near.
Camden generally expects a Construction Management Plan for basement work.
Spoil is the biggest logistical job: we plan conveyors, skips and lorry times with the neighbours before the first bucket of soil is lifted.
Sources: GOV.UK: Party walls and building work, Camden Local Plan 2017
A West End Lane basement
Questions about basements in West Hampstead
Is West Hampstead prone to flooding?
Camden guidance quoted in the neighbourhood plan identifies it as subject to localised surface water flooding.
Can I build a two-storey basement?
Camden's policy keeps basements to one storey, and the plan urges more caution below one storey because of shallow foundations.
Can I have a bedroom in a basement here?
Not where the area is prone to flooding: Camden does not permit habitable rooms in such basements.
Do I need planning permission for a basement?
Yes, everywhere in Camden since the 2017 Article 4 Direction.
Who prepares the Basement Impact Assessment?
A chartered engineer or chartered geologist for the technical reports, with a plain summary for everyone else.
What does a basement conversion in West Hampstead cost?
Pricing: quoted after a feasibility visit.
Sources: Fortune Green and West Hampstead Neighbourhood Plan (adopted by Camden, September 2015), Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021), Camden Council: Basement developments and planning applications
Sources
- Fortune Green and West Hampstead Neighbourhood Plan (adopted by Camden, September 2015)
- Camden Local Plan 2017
- Camden: South Hampstead Conservation Area Character Appraisal and Management Strategy (February 2011)
- Camden Planning Guidance: Basements (January 2021)
- Camden Council: Basement developments and planning applications
- GOV.UK: Party walls and building work
Guides & Local Reading
More Services in West Hampstead
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West Hampstead history & architecture
Background on the streets, buildings and conservation history of West Hampstead: The Village of West End Early History
Completed renovation project examples
