Area guide · N6
House Extensions in Highgate (N6)
Planning a house extension in Highgate? We design, gain planning permission and build extensions and loft conversions across N6 — from the village core to the Archway Road corridor. Most single-storey rear extensions here cost £60,000–£125,000 to build, your application goes to Haringey or Camden Council depending on which side of the High Street you live, and the most telling recent consent is Listed Building Consent for a single-storey rear extension to a Grade II listed home — proof that even Highgate's most protected houses can grow. The free site visit gives you a definitive answer on what your house, and its setting, will permit.
Live planning data
What the councils are actually approving in N6 right now
We keep a complete record of residential planning decisions across North London — evidence you can read before you commit, rather than assumptions you hope hold up. Highgate splits between two authorities: which side of the High Street you're on decides whether Haringey or Camden takes your application. In the most recent decision period, these are real N6 consents granted on the Haringey side:
- 28 Wood Lane, N6 — Listed Building Consent granted for works to a Grade II listed dwelling, including a single-storey rear extension (granted)
- 15A Cholmeley Park, N6 — certificate of lawfulness granted for outbuilding works (granted)
- 120 Archway Road, N6 — full redevelopment consent (granted)
Step back and both machines are turning: over the same two weeks, Haringey granted 32 residential approvals and Camden 31 on its side of the boundary.
Each consent carries a lesson. Wood Lane is the big one: listed homes can extend. With heritage-literate drawings and a proper justification, Listed Building Consent for a well-mannered rear addition is genuinely achievable — the blanket "you can't touch a listed building" myth costs Highgate owners space every year. Cholmeley Park shows the value of certificates of lawfulness: where works qualify, certificating them puts their legality beyond doubt. And Archway Road shows the corridor's appetite for more ambitious redevelopment.
Consents listed here come from the public records of Haringey and Camden councils. We didn't build them — they're cited to show what's being granted — and any application's fate depends entirely on its own circumstances.
Local knowledge
Highgate's housing stock — and what works on each
Highgate is the most rarefied market we work in alongside Hampstead — and the most layered.
The village core. Georgian and early-Victorian houses on and around the High Street, many of them listed, virtually all inside the large Highgate conservation area. The winning projects here are high-specification single-storey rears (£60,000–£125,000) with exceptional glazing and brick-matching, and sensitively engineered basements where the plot allows — basements are bespoke and priced case-by-case, beyond any standard table. Listed homes need Listed Building Consent for almost any alteration; as Wood Lane shows, that's a process, not a prohibition.
The Haringey side — Cholmeley Park down towards Archway Road. Substantial Victorian semis and terraces on the slopes. Loft conversions with rear dormers (£70,000–£125,000), rear extensions and garden buildings all feature here — the Cholmeley Park certificate shows outbuilding works going through with their lawfulness confirmed.
The Camden side — down towards the Heath. Early-Victorian villas and terraces under Camden's planning regime, with the same conservation discipline. Camden granted 31 residential approvals in the recent window, so the machine is moving on that side of the line too.
The Archway Road corridor. Victorian terraces at Highgate's relative-value end — natural territory for the side-return extension (£45,000–£90,000) and dormer loft, and, as 120 Archway Road shows, the occasional full redevelopment.
Every street is different. That's the point.
We design to Highgate's stock and to what the council demonstrably approves — not to a template. A free site visit tells you what your house can take.
Get my free estimateHonest numbers
What a house extension costs in Highgate in 2026
Highgate carries the strongest premium in our patch — typically 30–40% above the North London baseline, with £3,500–£5,000 per square metre realistic for quality work (the baseline elsewhere is £2,800–£4,200/m²). All figures are all-in build ranges; VAT, professional fees and kitchen fit-out come on top:
| Extension type | Typical Highgate cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £45,000 – £90,000 | 2–3 months | Often full application here |
| Single-storey rear | £60,000 – £125,000 | 3–4 months | Full application in the conservation area |
| Kitchen extension (incl. mid-range kitchen) | £70,000 – £155,000 | 3–4 months | Full application in the conservation area |
| Loft conversion + rear dormer | £70,000 – £125,000 | 6–10 weeks | PD outside the conservation area |
| Wrap-around extension | £90,000 – £195,000 | 4–6 months | Full application |
| Double-storey rear | £100,000 – £220,000 | 5–7 months | Full application |
| Garage conversion | £25,000 – £50,000 | 4–6 weeks | Usually permitted development |
Apply those rates to an 18m² rear addition and you're looking at £63,000–£90,000 of build cost in N6. The premium isn't padding: conservation-grade materials, heritage joinery, tight access on village streets and the finish level Highgate buyers expect all cost real money. After we've walked the property, the quote we give is fixed and itemised down to the line — the sum you commit to is the sum you part with.
Permissions, handled
Planning permission in Highgate — what you need to know
First, establish your council. The village straddles the Haringey–Camden boundary, and which side of the High Street you're on decides who determines your application. We confirm it from your address before any design work.
Then, establish your constraints. Much of N6 sits inside the Highgate conservation area, where permitted development rights are restricted — schemes that would be PD elsewhere need full applications here. Listed buildings go further still: Listed Building Consent is needed for external and internal works alike, and listed homes have no permitted development fallback. Outside the conservation area, the standard rules apply: permitted development allows rear extensions of 3m on semis and terraces and 4m on detached homes, the larger home extension prior-approval route opens up 6m and 8m, and loft conversions draw on a generous volume allowance.
On either side of the line, a standard householder application takes in the order of eight weeks to decide; Listed Building Consent runs to a similar clock but rewards extra preparation time. Party walls apply to most terraced and semi-detached projects — budget £1,000–£2,500 per affected neighbour if surveyors are appointed; we serve the notices as part of the job. And wherever an element of your project proceeds without full permission, we obtain a Lawful Development Certificate — exactly the route taken at Cholmeley Park — so there's no ambiguity when you sell.
How it works
How it works
- Free site visit — we visit your N6 home, weigh up its setting — conservation area, listed status, access — and advise frankly on feasibility, cost and consent strategy.
- Design & drawings — heritage-aware plans and 3D visuals that honour the house, its context and the way you live in it.
- Planning, handled — we prepare the full submission for Haringey or Camden, conservation statements and listed-building paperwork included, and manage it to decision.
- Fixed-price build — execution by our vetted North London team, certified by building control, completed with a meticulous handover.
When the Highgate project outgrows the side return
Highgate's conservation streets hide some of North London's most ambitious private builds: double-storey reworks behind Georgian and Victorian fronts, basements under the hill, whole houses reorganised around light and garden. Once a brief reaches whole-house scale it changes category, and the design and consent strategy should change with it.
That category is served by our large and luxury extensions offer, priced fixed and banded honestly in the luxury extension cost guide.
Our work
Recent work near Highgate
Among the team's recent North London work: a full house transformation taking a family home from 120m² to 360m² — the scale of ambition Highgate projects often share — a 55m² garden room with kitchen and bathroom, and an Edwardian conversion in Finchley. Request comparable examples at the visit and we'll select the work that speaks most directly to your scheme.
Questions, answered
Highgate extension FAQs
My Highgate house is listed — is an extension off the table?
No. The recent consent at 28 Wood Lane — Listed Building Consent for works to a Grade II listed home including a single-storey rear extension — is the proof. Listed buildings demand heritage-literate design and a strong justification, but well-conceived rear additions are being granted in N6.
Which council will decide my application — Haringey or Camden?
It depends which side of the High Street you're on; the village straddles the borough boundary. The policies and conservation officers differ, so we confirm your authority on day one and design to its grain.
Why do Highgate extensions cost more than the rest of North London?
Expect £3,500–£5,000/m² against a £2,800–£4,200/m² North London baseline — roughly 30–40% over. Conservation-grade materials and joinery, listed-building care, constrained access on village streets and a higher finish specification all add genuine cost, not margin.
Can I put an outbuilding or garden room in my Highgate garden?
Often, yes — garden buildings can fall under permitted development even where extensions don't, subject to size, height and conservation-area limits. The certificate of lawfulness granted at 15A Cholmeley Park shows the smart route: confirm the works' lawful status in writing before you build.
How long does consent take in the Highgate conservation area?
Around eight weeks for a standard householder application once validated, on either side of the borough line. Listed Building Consent runs on a similar timetable — the real schedule driver is getting the heritage detail right before submission, and we build that time in.
Is a Lawful Development Certificate worth it in N6?
More than almost anywhere. With permitted development restricted across the conservation area, buyers' solicitors ask hard questions about any uncertificated works. An LDC settles them in advance — we obtain one whenever part of your project proceeds without full permission.
Nearby areas we cover
What clients say
Rated 5.0 on Google
“Used The Extension Company for a loft conversion on our semi detached in Barnet and couldn't be happier. They explained what was possible at the first visit, sorted the planning side, and gave a fixed price with no surprises at the end.…” read the full review
“Really impressed with the entire project. The side extension and conservatory have been finished to a very high standard and the team made the process straight forward and stress-free. It’s transformed the space and added so much value, would definitely recommend.”
“Brilliant experience with the extension company, transparent from the word go. Completed a double story extension for me and I couldn’t be more pleased. Thank you”
“I got the extension company to do a bathroom refurb for us a January they done a great job they managed to fit in a large shower as well as a bath”
Reviews shown word for word from our Google profile. Read all 8 reviews on Google
Free site visit
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Free site visit anywhere in Highgate, honest feasibility advice and a fixed, itemised price — design, planning and build handled end to end by the Pine Grove team.
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