Basement
conversions
in Kentish Town, NW5
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Kentish Town lies in the valley of the buried Fleet, and Camden's appraisals are wary of digging under its terraces and gardens.
Camden's Kentish Town appraisal sets the whole district in the old river valley of the Fleet, whose course Kentish Town Road still traces even though the water now runs underground.
Before any basement is drawn, our engineer studies the ground, the water and the neighbouring foundations, and we report what they find in plain terms.
Source: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
The Fleet under the streets
According to Inkerman's statement, culverting had reached Holmes Road by the 1850s, and the last open stretch to the north was enclosed in 1872 after the cholera of 1866.
A Camden Basement Impact Assessment moves through screening and scoping, then site investigation and study, then the assessment itself, and ends with review and decision.
The desk study maps old watercourses, sewers and soil records first; boreholes and trial pits follow only if the scheme goes ahead.
Sources: Camden: Inkerman Conservation Area Statement (March 2003), Camden Planning Guidance: Basements (January 2021)
Basements in the Kentish Town Conservation Area
Camden's management strategy for the area notes a rise in new basements and lightwells across Camden's conservation areas, and says it will resist those that would harm the area's character and appearance.
A fresh lightwell can cut the house off from its street and eat into the garden; the railings it needs make the front look busy.
Glass laid into a front garden to light a room below brings a glow at night that the strategy counts as harm to the garden setting.
Its appraisal names basement extensions, with roof extensions and back-garden infill, as threats to the area's quality.
Source: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
Policy A5 of the Camden Local Plan
Under Policy A5, Camden has to be satisfied that a basement will cause no harm to neighbours, to the structure, ground and water, to the area's character or to heritage.
The policy limits a basement to a single storey, never beneath an existing one, covering at most half of any garden.
The impact assessment has to keep forecast damage next door at Burland category 1, the very slight end of the scale.
Since 1 June 2017 an Article 4 Direction has meant that no basement or lightwell dig in Camden is permitted development.
Sources: Camden Local Plan 2017, Camden Planning Guidance: Basements (January 2021)
Houses that already have a lower floor
On Islip Street, some houses stand over basement areas behind raised front doors, and in Alma Street some have half or full basements.
Others were built without: Patshull Road's front doors open at street level with no basement area, and none of Ryland Road's houses has a full basement.
For Inkerman houses, the statement accepts work into basement areas only where it leaves the house and its setting unharmed.
Where a lower floor exists, lining it, lowering it a little and improving the light is usually the first option we price.
Sources: Camden: Bartholomew Estate Conservation Area Statement (adopted 2000), Camden: Inkerman Conservation Area Statement (March 2003)
Gardens, trees and soil cover
Camden's Kentish Town strategy sets itself against losing gardens, planting, old boundary walls and railings to basement schemes.
Inkerman's statement wants each tree standing within 10 metres of a proposal marked, below-ground work included.
Any basement reaching past the house footprint should carry a metre or more of soil above it, Camden's guidance says.
Sources: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011), Camden: Inkerman Conservation Area Statement (March 2003), Camden Planning Guidance: Basements (January 2021)
Neighbours and the stability of the terrace
In the conservation area, Camden wants to see effective measures keeping the house and the houses either side stable through demolition and construction.
GOV.UK requires notice to a neighbour before digging beneath and close to the level of their foundations.
Camden's Local Plan says a Construction Management Plan will generally be needed.
In a terrace the dig is always next to someone's foundations, so we agree monitoring points on both party walls before the first underpin.
Sources: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011), GOV.UK: Party walls and building work, Camden Local Plan 2017
Basements and divided houses
Creating extra flats by digging out a basement will not normally be accepted in the Kentish Town Conservation Area if it harms the area's character, the strategy says.
Extending an existing ground-floor flat downwards is not the same as adding a flat, so our drawings and planning statement show plainly which is proposed.
Source: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
Highgate Road addresses in Dartmouth Park
Very few houses in Camden's Dartmouth Park Conservation Area show basement work from the road, and the council will normally resist new basements there that face the highway.
Its basement guidance warns that a lightwell will consume most of a shallow front garden and is unlikely to be agreed on a street where lightwells are not already part of the scene.
Sources: Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009), Camden Planning Guidance: Basements (January 2021)
The assessment, in words anyone can read
Each Basement Impact Assessment should open with a plain summary of its evidence for readers with no technical background.
Camden asks for subsidence risk to be graded on the Burland Scale, which ranks damage by how easily it could be put right.
We share that summary with the neighbours before the application, along with how the dig will be monitored.
Source: Camden Planning Guidance: Basements (January 2021)
How a basement goes in under a terrace
Under a terrace the walls are underpinned in short, alternating bays, so no length of the party wall is left unsupported. Each bay is dug, concreted and allowed to gain strength before its neighbour is opened.
Temporary props carry the ground floor while the new slab and retaining walls are built, and the waterproofing goes in as two systems: a drained cavity membrane inside and a sump with a pump and a backup.
The floor above is checked for level throughout, and the readings go to the party wall surveyors.
Spoil, skips and the street
A skip on a Camden road needs a licence that only the skip company can request, at least five working days before it arrives.
Spoil leaves by conveyor from the back or through the house on protected runs, into skips or a muck-away lorry booked for quiet times of day. We agree the loading point with the neighbours before the first bucket is lifted.
Where the pavement has old York stone, we board it over for the whole dig and photograph it first.
Source: Camden Council: skip licence
Questions about basements in Kentish Town
Will Camden accept a basement in the Kentish Town Conservation Area?
Only where it does not harm the area's character, and with proof the house and its neighbours stay stable while it is built.
Is a basement ever permitted development in Camden?
No; the borough-wide Article 4 Direction of June 2017 brought every basement dig under planning control.
How large can a basement be under Policy A5?
One storey, not under an existing basement, and over no more than half of any garden.
Is a front lightwell likely to be allowed?
Camden's Kentish Town strategy says a new lightwell can harm the street and swallow garden, so it is a hard case to make.
Do the neighbours have to be told before the dig?
Yes: digging beneath and near their foundation level is notifiable under the Party Wall Act.
What does a basement conversion in Kentish Town cost?
Pricing: quoted after a feasibility visit.
Sources: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011), Camden Planning Guidance: Basements (January 2021), Camden Local Plan 2017, GOV.UK: Party walls and building work
Related pages
Sources
- Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
- Camden: Inkerman Conservation Area Statement (March 2003)
- Camden Planning Guidance: Basements (January 2021)
- Camden Local Plan 2017
- Camden: Bartholomew Estate Conservation Area Statement (adopted 2000)
- GOV.UK: Party walls and building work
- Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
- Camden Council: skip licence
Guides & Local Reading
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Kentish Town history & architecture
Background on the streets, buildings and conservation history of Kentish Town: The Atmosphere of Kentish Town Roads