House extensions near Parliament Hill and South End Green
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Hampstead Chartered Surveyors & Building ConsultancyRear and side extensions for houses near Parliament Hill and South End Green, drawn to Camden's tests for scale, daylight and light spill, with trees, drains and the Heath edge mapped before the first sketch.
Before extending at ground level, Camden recommends a preliminary site assessment: the existing rear elevation and earlier extensions, how visible the back is from gardens and the street, and what the neighbours have already built.
We carry out that assessment at the first visit and photograph the neighbouring backs as well as your own.
Source: Camden Planning Guidance: Home Improvements (January 2021)
Scale, Materials and Design
Camden looks for a rear addition that is clearly secondary to the house: smaller in its footprint and scale, placed and shaped to suit it, detailed in matching or sympathetic materials, and leaving its bays, cornices and chimney stacks readable.
Side extensions should normally be single storey, though in some cases a taller one could be allowed.
Some sites suit a contemporary design that solves a constraint, Camden accepts; on others, an addition built to look like the house sits better.
Source: Camden Planning Guidance: Home Improvements (January 2021)
Daylight, Light Spill and Green Roofs
A rear extension should pass the 45-degree and 25-degree tests in Camden's amenity guidance or show, through a daylight test, that it meets BRE guidance.
Rooflights on a ground-floor extension should sit back from the building line or use obscured glass, to limit light spill, especially where the house is divided into flats.
On a flat roof, Camden prefers a biodiverse green roof with 100mm of substrate to sedum.
The extension should still leave a reasonably sized garden.
Source: Camden Planning Guidance: Home Improvements (January 2021)
Permitted Development and Prior Approval
In a conservation area, government guidance rules out permitted development for cladding, for extending beyond a side wall and for a rear extension of more than one storey.
The Planning Portal's prior approval route applies only to larger single-storey rear extensions, between four and eight metres beyond the original rear wall for detached houses and between three and six metres for others.
The original house means the house as first built, or as it stood on 1 July 1948 if older, so earlier owners' additions count.
Rights can also have been withdrawn for a particular house, by an Article 4 direction or by a condition on an old permission; a Lawful Development Certificate from Camden settles whether an application is needed.
Sources: MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), Planning Portal: Extensions, Prior approval
Trees, Clay and Foundations
In a conservation area, Camden needs advance notice of work to a tree with a trunk more than 75mm in diameter at 1.5 metres.
Some clay soils swell and shrink with moisture, so foundations go deeper, and trees in clay areas can push them much deeper than first planned, the Planning Portal says.
The Planning Portal's good practice is to take new foundations down at least as far as the neighbouring footing, and to dig and pour beside it a short length at a time so it is never undermined.
Sources: Camden Council: Conservation areas, Planning Portal: Extensions, Building Regulations: Foundations
Pre-Application Advice and the Heritage Statement
Camden's second level of homeowner pre-application advice is for larger or combined works, such as two-storey rear extensions, more than one extension, roof extensions, basements and whole-house remodelling.
The application must come with a heritage statement in a conservation area: Camden wants the significance of the house and its setting set out, and any harm justified clearly and convincingly.
We prepare the drawings, photographs and statement once and use them for both the pre-application request and the application, so the advice is given on the scheme that will be submitted.
Sources: Camden Council: Pre-planning application advice for homeowners, Camden Council: Conservation areas
Drains, Sewers and Openings
A recorded drain or sewer within 3 metres of the new walls, measured to its centreline, brings in the building-over-sewers section of Approved Document H.
For a sewer more than 3 metres deep or above 225mm in diameter, the sewerage company, as owner of a public sewer, has to give permission before anything is built over or within 3 metres of it.
Where the extension opens into the house, the rear wall above the new opening sits on new beams, each with a proper bearing at its ends.
Sources: GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition), Planning Portal: Extensions, Building Regulations: Structural Opening
Extensions we have completed nearby
Questions about extending near the Heath
How large can a side extension be?
Camden's guidance says side extensions should normally be single storey, though a taller one could be permitted in some instances.
Does prior approval apply in a conservation area?
The prior approval route covers larger single-storey rear extensions only, and in a conservation area a rear extension of more than one storey is not permitted development.
Will the extension's rooflights be an issue?
They can be: Camden asks for rooflights set back from the building line or obscured, to limit light spill on neighbours.
Is there a drain under the garden?
Check the sewerage company's records; building within 3m of a drain or sewer brings Approved Document H's provisions into play.
Can I confirm a proposal needs no application?
Yes. A Lawful Development Certificate from Camden can confirm whether a proposal is lawful without a planning application.
Sources: Camden Planning Guidance: Home Improvements (January 2021), Planning Portal: Extensions, Prior approval, MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
Sources
- Camden Planning Guidance: Home Improvements (January 2021)
- MHCLG: Permitted development rights for householders, Technical Guidance (September 2019)
- Planning Portal: Extensions, Prior approval
- Camden Council: Conservation areas
- Planning Portal: Extensions, Building Regulations: Foundations
- Camden Council: Pre-planning application advice for homeowners
- GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
- Planning Portal: Extensions, Building Regulations: Structural Opening
Extending a house near Parliament Hill and South End Green
Camden's South Hill Park statement says rear extensions should be as unobtrusive as possible and in most cases no more than one storey high, and that two-storey side extensions would generally not be acceptable. It adds that in some sensitive cases no extension or further extension can be permitted, in particular for properties that back onto Hampstead Heath and are included within the Article 4 direction, which Camden lists for 32–66 and 72–90 (even) South Hill Park, NW3.
The statement records that the houses on the west side of South Hill Park and the east side of Tanza Road back onto Hampstead Heath and Parliament Hill, and treats development on the fringes of the Heath as particularly sensitive.
The Hampstead Neighbourhood Plan, adopted by Camden on 21 July 2025, reaches South End Green. It designates Heath Edge Gardens, Parliament Hill and South Hill Park as a biodiversity corridor, and says acceptable garden buildings should sit on piled foundations or point supports rather than reinforced concrete slabs. It also explains that hard standing and larger building footprints on Hampstead's sloping streets add surface run-off, increasing flood risk in storm periods for lower areas such as South End Green and Fleet Road.
Sources: Camden Council — South Hill Park Conservation Area Statement (scanned PDF; quotes transcribed from the page images, printed page numbers); Camden Council — Article 4 directions for heritage and conservation; Camden Council — Hampstead Neighbourhood Forum and Neighbourhood Plan page; Hampstead Neighbourhood Plan 2025–2040, as adopted by Camden Council
For homes in Hampstead village itself, see house extensions in Hampstead, NW3.
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