Basement
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in Dartmouth Park, NW5
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Plenty of Dartmouth Park houses already have a lower floor at garden level, and Camden looks very differently at improving it than at digging a new one.
The appraisal finds very few houses in the conservation area with basement work showing to the road, and says Camden will normally resist basements that face the highway.
We start with the lower floor that is already there: its height, its damp and its stair, before excavation comes up.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Lower floors that already exist
Croftdown Road was built up above its gardens, so its houses have garden-level sub-basements that seldom show at the front on the north side.
On the west side of Brookfield Park the ground falls away, and many houses have basements on the garden side.
The villas of Dartmouth Park Road west stand over semi-basements.
Tanking, rewiring and opening an existing lower floor to the garden is often the better project; we confirm with Camden whether any lowering of the floor needs planning permission.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Why front lightwells are resisted
Camden says a lightwell facing the street would harm the house's relationship with it and would probably take most or all of the small front garden, while railings round it would clutter the front and compete with the boundary wall.
Rooflights set into a front garden can spill light from the rooms below and spoil the garden's setting.
Light for a lower floor here comes from the garden side: a wider opening, a glazed door or a modest rear lightwell set off the boundary.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
The buried stream
A principal tributary of the Fleet, culverted in the 1890s, crossed Highgate Road at Swains Lane and ran along Brookfield Park, York Rise and Burghley Road.
York Rise follows a branch of the river, and few buildings face onto it.
Near that line we ask for a ground investigation with groundwater monitoring before any basement design starts.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Digging into a slope
The ground drops about 35 metres from north to south across the area, with smaller valleys crossing it.
On Dartmouth Park Avenue the houses on the east side sit above the street, and gaps on the west side look down a steep escarpment.
On a sloping plot the retaining walls and the neighbours' footings, uphill and downhill, are designed as one problem.
Spoil leaves by small lorry at agreed times, and the order of digging is set by the engineer so that each section is propped before the next is opened.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Policy A5 and the Basement Impact Assessment
Under Policy A5 of Camden's Local Plan 2017, a basement is acceptable only if it does no harm to neighbours, the structure, the ground or water conditions, or the character of the area.
Its size tests include a single storey, at most half of each garden dug out, and an area below one and a half times the footprint of the building.
The assessment must keep the risk to neighbours within Burland Category 1, very slight, and moves through screening, scoping, investigation, impact assessment and review.
Camden wants its technical reports written by a chartered engineer or a chartered geologist with the right qualifications.
Sources: Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021), Camden Council: Basement developments and planning applications
Permission for every excavation
Since 1 June 2017 an Article 4 Direction across Camden has removed permitted development for basements, so digging any basement or lightwell now needs planning permission.
Camden generally asks for a construction management plan with basement schemes, and expects one for any basement proposal inside a conservation area.
Sources: Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017
Party walls and neighbours
Digging near a neighbour's foundations, or working on a party wall, means telling the neighbour first under the Party Wall etc Act 1996.
If the owners cannot agree, one or two surveyors draw up a binding document setting out what is done, how and when.
We meet the neighbours on both sides before the notices go out, with the engineer's drawings on the table.
Source: GOV.UK: Party walls and building work
Trees and the soil above
An arboricultural report is required where trees stand on or beside the site.
Where a basement runs beyond the house's footprint, Camden expects a metre or more of soil above it.
Policy ES2 asks for significant trees to be kept and protected while the work goes on.
Sources: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009), Camden Planning Guidance: Basements (January 2021), Dartmouth Park Neighbourhood Plan (made by Camden, 2 March 2020)
Gardens Camden wants kept
Camden will resist the loss of soft landscaping and of original walls and railings in front and back gardens.
The appraisal counts building on large green backland plots among the pressures on the area.
A lower floor under part of the house rather than under the garden keeps the planting ground and the roots intact.
Source: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Basements in listed houses
Most Grove Terrace houses have area basements, attics and mansards, and Nos 6 to 27 are listed Grade II*.
Any new or extended basement in a listed building needs listed building consent as well as planning permission.
For a listed house we record the existing lower floor first and propose repairs before any change of level.
Sources: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009), Camden Planning Guidance: Basements (January 2021)
Flood risk
Camden will not permit habitable basement rooms where flooding is a risk.
We check Camden's flood mapping for the address and design the drainage, sump and pump for the lower floor in every case.
Source: Camden Local Plan 2017
Questions about basements in Dartmouth Park
Can I dig a basement under the front garden?
Camden will normally resist basements and lightwells facing the road in the conservation area.
Do I need planning permission for a basement in Camden?
Yes; since June 2017 digging any basement or lightwell has needed it.
What depth does Camden allow?
A single storey, and none below an existing basement, under Policy A5.
Is there water under Dartmouth Park?
A culverted tributary of the Fleet runs along Brookfield Park, York Rise and Burghley Road, so the ground needs investigating.
Will my neighbours be affected?
The assessment has to hold the risk of damage to them within Burland Category 1.
Does a listed house need extra consent for a basement?
Yes: a new or enlarged basement in a listed house needs listed building consent.
Sources: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009), Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017
Related pages
Sources
- Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
- Camden Local Plan 2017
- Camden Planning Guidance: Basements (January 2021)
- Camden Council: Basement developments and planning applications
- GOV.UK: Party walls and building work
- Dartmouth Park Neighbourhood Plan (made by Camden, 2 March 2020)
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