House Extensions Highgate
Single and double storey extensions in Highgate, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation plans and builds extensions across Highgate, adding space to N6's Victorian and Edwardian houses without losing their period feel. We handle groundworks, steel, roofing and fit-out under one roof. Planning goes to Camden or Haringey depending on which side of the High Street you are, and we confirm the route from the start.
In Highgate, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Highgate: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Highgate
Highgate range: choose above
Side-return extensions in Highgate terraces
The side-return infill is the signature Highgate extension. These Victorian and Edwardian terraces have a narrow alley of dead space beside the rear closet wing, and building across it widens the kitchen into a bright, open-plan room. We dig new foundations next to the existing wall, tie in carefully, and install a steel beam where the old external wall comes out, all sized by a structural engineer and inspected by building control.
A wrap-around scheme takes the side return and a rear extension together, giving a generous kitchen-diner that opens onto the garden. Rooflights and glazed doors bring in light, which matters on the shaded, mature plots common near the Heath. Because the flank wall is usually shared, you serve party wall notice on the neighbour early, and we build to any award and coordinate the drainage, roofing and internal steels as a single sequence.
Housing in Highgate
For Highgate the Council Tax list gives about 10,090 homes; by type 69% flats and 31% houses, by age 28% post-war, 24% interwar and 47% older than 1919. Since most homes here are flats, a flat in Highgate has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Trees, pre-planning advice and a Highgate rear extension
Where a plot near the Heath or Waterlow Park has trees close to the house, a rear extension can need roots or branches cut. Camden requires six weeks' notice before tree work in a conservation area, for any tree with a trunk diameter of more than 75mm at a height of 1.5 metres. That applies to a neighbour's tree overhanging the footprint as much as to your own. Give the notice as soon as the foundation line is known, so the six weeks run while drawings are finished, and have the engineer design any foundations near roots on the basis of the tree staying.
The size of the scheme sets the advice level. Camden's Level 2 homeowner pre-planning application advice covers multiple or more complex works, such as more than one extension or two storey rear extensions, and a Highgate wrap-around or two storey rear addition belongs there. A planning application for alterations in a Camden conservation area must include a heritage statement describing the significance of the heritage assets affected. Take a draft of that statement, a measured survey and photographs of the neighbouring rear elevations to the meeting, because they are what the advice will be based on.
Planning and permitted development in Highgate
Whether your extension is permitted development or needs a full planning application depends on the property. Many single-storey rear extensions in N6 fall under permitted development, but Highgate has conservation areas where those rights are restricted, and any flat, listed building or previously extended house is likely to need a full application to Camden or Haringey Council, whichever covers the address. We assess your specific house before drawing anything.
Double-storey and wrap-around schemes almost always need planning permission, and your architect or designer prepares the drawings; we can recommend one and coordinate the submission with them. Separately, every extension needs building regulations approval for its foundations, steelwork, insulation and drainage, which is a different process from planning and one we handle throughout. Getting both routes right from the outset avoids the delays and enforcement risks that catch out unprepared Highgate projects.
Kitchen extensions in Highgate
69% of homes in Highgate are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Camden Council or Haringey Council and the freeholder's consent. Most kitchen extensions here are on the 31% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Highgate; the build figures are in the table above.
Double storey extensions in Highgate
Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Highgate often needs planning permission from Camden Council or Haringey Council. It is a job for the 31% of homes that are houses; a flat cannot add a storey this way. Highgate was designated as a Conservation Area in 1968 and extended in 1978 and 1992 (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Flat and pitched roofs with rooflights or lanterns
- Building control inspections at foundation, damp course and steel stages
- Steel goalpost frames where the rear wall opens up
VOA Council Tax stock of properties, March 2025, for Highgate West, Highgate East and Highgate Wood. Counts rounded by the VOA.
Why Choose GS Renovation in Highgate
Homeowners across N6 choose us because we run the whole extension, from the first planning conversation with Camden or Haringey Council to the final coat of paint. Our founder's 30+ years on the tools means we know how these side returns and closet wings behave, how to found next to old walls, and how to keep a family home liveable while we build.
- Garden levels and access made good where the build meets outside
- Founder with 30+ years of hands-on experience
- Building control inspected at foundation, damp course and steel stages
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
It's the second time I have hired George and he has been absolutely professional and the work he did resembles perfectly what I had in mind. Being an…
We loved working with George and Ibrahim and would highly recommend them. They have done splendid job on our new kitchen refurb which including new…
FAQ
Frequently Asked Questions about House Extensions Highgate
How much should house extensions in Highgate cost?
In Highgate, house extensions will usually fall within £2,000 to £2,800 per m² for a rear extension (indicative), yet two homes of the same size can still land far apart. Sequence explains most of the gap: the steel into the house is designed before the rear wall comes down, and a quotation that skips a step is only cheaper on paper. GS Renovation prices each step as its own line for your N6 property.
Will my Highgate rear extension need planning permission or is it permitted development?
Many single-storey rear extensions in N6 are permitted development, but if you are in a Highgate conservation area, own a flat or listed building, or the house has already been extended, you will likely need a full application to Camden or Haringey Council. We check your property's history and constraints first, then advise the correct route before any design work.
Can I extend my ground floor Highgate flat into the garden?
Possibly, though a flat has no automatic allowance to build out. The size limits that let houses extend without an application do not cover flats, so the council decides it as a full planning application. The rear wall you want to open is usually the freeholder's structure, which makes their written consent the first document to secure. Building regulations then run exactly as for any other extension.
How do mature trees near a Highgate extension affect the foundations?
They push foundations deeper and sometimes change their type. Roots draw moisture from the ground, which can shrink clay soils beneath shallow footings, so the engineer checks each tree's species, height and distance before setting the depth. Near roots that must be kept, trenches are dug by hand. Building control inspects every trench before concrete is poured, and the depth is recorded for later.
Will a Highgate extension under mature trees still get enough daylight?
It can, with daylight brought in from above and planned around the shade. Rooflights set along the line nearest the house pull light into the middle of the plan, while a lantern suits a flat roof where leaves can be cleared. Under trees, a steeper glazed pitch sheds debris better, and self-cleaning glass helps. Glazing is balanced against Part L, so the amount is settled early.
Can the original rear wall stay inside my Highgate extension?
Partly. Where a house extension opens into the existing kitchen, the old rear wall is usually replaced by steel over a wide opening, but brickwork either side can stay as piers if the engineer confirms they can carry the beam ends. Keeping some wall reduces the steel needed and gives the new room a clear threshold. Building control inspects the steel and bearings before they are covered.
Does a large Highgate extension pay Camden's Community Infrastructure Levy?
Only if it adds 100 square metres of new floorspace or an extra dwelling, which is when Camden's levy applies. Camden's rate summary puts Highgate in Zone C, alongside Hampstead, separate from the central zone and the rest of the borough. A two storey rear extension plus a basement on a large Highgate house can approach that area, so total the new floorspace of the whole scheme before the planning application is submitted.
How can a Highgate owner tell whether the house is in the conservation area?
First confirm the address is in Camden, because the N6 postcode crosses a borough boundary, then check the boundary map for the current extent. Highgate was designated as a Conservation Area in 1968 and extended in 1978 and 1992, so an older survey, a previous planning decision or a neighbour's memory may predate the change. Being inside decides whether a heritage statement goes with the application and whether six weeks' tree notice applies, so confirm it before any designer is briefed.
Can a semi-detached Highgate house extend to the side and rear together?
It can, but inside the conservation area a side extension needs planning permission. 15% of Highgate homes are semi-detached or detached, and these are the plots with space at the side as well as the rear. A combined scheme counts as more complex works for pre-planning advice purposes, which Camden places at Level 2. A side extension built up to the boundary also brings in the Party Wall Act, and as building owner you serve those notices before work starts.
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