House
extensions
in Kentish Town, NW5
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Hampstead Chartered Surveyors & Building ConsultancyBehind most Kentish Town terraces lies a long, narrow garden, and Camden judges an extension by what it takes from that garden and the row of backs.
On the northern streets of the Kentish Town Conservation Area, Camden records small front gardens and longer rear gardens behind narrow three-storey terraces.
We design an extension here from the garden end inwards, deciding first how much of the garden must stay, then how much room that leaves.
Source: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
The row of backs
Inkerman's statement turns down rear extensions that would break an unspoilt terrace's matching backs, cut deep into the garden or spoil public views across the gardens.
The Bartholomew Estate statement applies much the same test to an unaltered terrace, and counts rear elevations and open gardens among the area's assets.
On the Highgate Road edge, the Dartmouth Park appraisal refuses rear extensions that stray far from the way the backs were first built.
We photograph the neighbours' rear walls from the garden, so the drawings show the row the new room will join.
Sources: Camden: Inkerman Conservation Area Statement (March 2003), Camden: Bartholomew Estate Conservation Area Statement (adopted 2000), Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
Height, width and depth
On the Bartholomew Estate the usual limit is a single storey across half the house's width, and where something taller is accepted it should be kept shallow.
Inkerman's statement asks rear additions to be discreet and, in most cases, one storey.
Camden's Home Improvements guidance wants every rear extension secondary to the house in footprint, scale and detail, respecting bays, cornices and chimney stacks.
A half-width extension beside the back addition often gives a kitchen and dining room without closing in the neighbour's window.
Sources: Camden: Bartholomew Estate Conservation Area Statement (adopted 2000), Camden: Inkerman Conservation Area Statement (March 2003), Camden Planning Guidance: Home Improvements (January 2021)
Gaps at terrace ends and side extensions
Inkerman's terraces keep clear gaps at their ends and between buildings; Camden normally resists filling an important one, and wants any other side addition low and stepped back from the front.
On Patshull Road and the streets around it, the gaps beside the semi-detached houses give glimpses of rear gardens that Camden wants kept.
Camden's Home Improvements guidance generally limits side extensions to one storey.
Sources: Camden: Inkerman Conservation Area Statement (March 2003), Camden: Bartholomew Estate Conservation Area Statement (adopted 2000), Camden Planning Guidance: Home Improvements (January 2021)
Trees, roots and the garden that remains
The Kentish Town appraisal prizes the mature trees in back gardens most where passers-by can glimpse them.
Before building, trees on or next to the site and their root protection zones must be considered, and an arboricultural report goes with the application.
After the extension, a garden of reasonable size has to remain, in Camden's guidance.
Where a tree stands near the line of the extension, we bring the arboriculturist in before the foundation design, not after.
Sources: Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011), Camden Planning Guidance: Home Improvements (January 2021)
Glass roofs, rooflights and neighbours above
Camden asks that a rear extension does not flood neighbours with light at night, and that includes flats upstairs in a subdivided house.
A ground-floor rooflight is better placed well away from the main wall, or glazed in obscured glass.
Inkerman's statement keeps conservatories small, subordinate and at ground level only.
In a divided house we show the upstairs flat the night-time view from its window before the scheme is fixed.
Sources: Camden Planning Guidance: Home Improvements (January 2021), Camden: Inkerman Conservation Area Statement (March 2003)
Permitted development and divided houses
Government guidance takes side extensions and anything over one storey at the rear out of permitted development in conservation areas.
Flats have no householder rights at all, and Camden's Bartholomew Estate statement adds that subdivision has stripped most of that estate's houses of them.
If you want certainty that no application is needed, the council can issue a Lawful Development Certificate.
Sources: MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), Camden: Bartholomew Estate Conservation Area Statement (adopted 2000)
Foundations, drains and building control
Nearly every extension also needs building regulations approval, the Planning Portal says.
On clay that swells and shrinks with the weather, footings go deeper, and deeper still where tree roots are close.
Next to an existing footing the trench should reach its base and be dug and concreted a short length at a time.
Approved Document H applies to building within 3 metres of the centreline of a drain or sewer on the sewer records.
In a terrace the shared drain often runs under the yard, so we find it with a camera survey before drawing the footprint.
Sources: Planning Portal: Is building regulations approval needed for an extension?, Planning Portal: Extensions, Building Regulations: Foundations, GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
Design cues from the neighbourhood plan
Policy D3 of the Kentish Town Neighbourhood Plan asks extensions to draw on local cues such as grain, form, scale, height, massing, detailing and boundaries.
It also asks for materials that complement those of the surrounding buildings.
On a flat roof Camden would rather see a biodiverse green roof on 100mm of growing medium than sedum.
On a stock brick terrace that usually means reclaimed or matched brick, or a lighter structure that clearly reads as new.
Sources: Kentish Town Neighbourhood Plan (adopted by Camden, September 2016), Part 2, Camden Planning Guidance: Home Improvements (January 2021)
Daylight tests and pre-application advice
Neighbours' light is checked with Camden's 45-degree and 25-degree rules, or with a BRE daylight study instead.
Camden's guidance suggests studying the house's back, its earlier additions and next door's before any design begins.
For a single-storey rear extension, Camden's lighter pre-application service is the usual route.
Sources: Camden Planning Guidance: Home Improvements (January 2021), Camden Council: Pre-planning application advice for homeowners
What helps us price an extension
A few photographs go a long way: the rear wall, the garden from an upper window, and next door's extension if there is one. Old drawings or consents for the house help us see what has been built before.
Say how the room will be used day to day. A family kitchen, a quiet study and a playroom ask for different orientation, storage and heating, and the plan changes with them.
Mention any tree near the boundary and any manhole in the yard, so the first visit can confirm both.
Questions about extending a Kentish Town house
How big can my rear extension be on the Bartholomew Estate?
Camden's statement points to a single storey across half the house's width in most cases, kept shallow if taller.
Can I infill the gap at the end of my terrace?
In the Inkerman area, infilling an important gap is normally resisted, and other side additions should stay one storey and stepped back.
Do I need permission for a two-storey rear extension?
In a conservation area, yes: government guidance excludes rear additions of more than one storey from permitted development.
Will Camden want a tree report?
If there are trees on or next to the site, including street trees, an arboricultural report goes with the application.
Can I build a conservatory on the first floor?
Not in the Inkerman area: its statement keeps conservatories at ground level only.
What does a house extension in Kentish Town cost?
Pricing: quoted after a feasibility visit.
Sources: Camden: Bartholomew Estate Conservation Area Statement (adopted 2000), Camden: Inkerman Conservation Area Statement (March 2003), MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
Related pages
Sources
- Camden: Kentish Town Conservation Area Appraisal and Management Strategy (adopted 11 March 2011)
- Camden: Inkerman Conservation Area Statement (March 2003)
- Camden: Bartholomew Estate Conservation Area Statement (adopted 2000)
- Camden: Dartmouth Park Conservation Area Appraisal and Management Statement (adopted 22 January 2009)
- Camden Planning Guidance: Home Improvements (January 2021)
- MHCLG: Permitted development rights for householders, Technical Guidance (September 2019)
- Planning Portal: Is building regulations approval needed for an extension?
- Planning Portal: Extensions, Building Regulations: Foundations
- GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
- Kentish Town Neighbourhood Plan (adopted by Camden, September 2016), Part 2
- Camden Council: Pre-planning application advice for homeowners
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