Area guide · NW3
House Extensions in Hampstead (NW3)
Planning a house extension in Hampstead? We design, gain consent and build extensions across NW3's Georgian and Victorian stock — conservation area, listed buildings and all. Count on £90,000–£180,000 to build a single-storey rear, with applications going through Camden Council — and the schemes being approved right now are exactly what you'd expect of NW3: high-spec rear extensions, basements and listed building consents. Planning-heavy is normal in Hampstead — and it's precisely what we do. It begins with a free site visit, where we chart the consent route for your exact address.
Live planning data
What Camden Council is approving right now
North London's residential planning decisions all flow through our tracking system — so you can see what actually passes before committing to a design. In the most recent two-week decision window, Camden Council approved 31 residential schemes across the borough, and the mix says everything about this market:
- High-specification rear extensions — design-led schemes with the materials and glazing to match the houses they extend
- Basement schemes — the Camden speciality, approved against the borough's strict basement policy with full impact assessments
- Listed building consents — alterations to protected homes that needed a second, more exacting layer of permission, and earned it
There's a lesson in that list. Hampstead's reputation says "you'll never get it through"; the record says conservation-area and listed-building schemes pass in Camden week in, week out. The difference is that the successful ones are designed for scrutiny from the first sketch — not patched up after a refusal. That's the work we do, and in NW3 it's the norm, not the exception.
Source: Camden Council's public planning register. Read it as borough-wide context rather than our CV — none of these are our jobs, and each application lives or dies by its own circumstances.
Local knowledge
Hampstead's housing stock — and what works on each
The Georgian core. The lanes of old Hampstead hold some of London's finest Georgian houses, and a remarkable number are listed — which means listed building consent for alterations, inside and out, on top of planning permission. Extending here is a design exercise in the best sense: restrained massing, traditional materials and craftsmanship that can stand next to 250-year-old brickwork without embarrassment. Slower, more considered, and deeply worth it.
Victorian terraces and semis. The bulk of NW3 is high Victorian — generous ceilings, robust brick, gardens that reward a glass-and-brick rear extension. Side-returns (£50,000–£100,000) and single-storey rears (£90,000–£180,000) are the bread and butter; within the conservation area they go through full applications, with materials and rooflines scrutinised, and the results justify the process.
Basements — the Camden speciality. Where you can't go out and can't go up, Hampstead goes down. Camden runs the most developed basement policy in London: expect a Basement Impact Assessment covering ground conditions, groundwater and the structural effect on neighbouring buildings before consent is granted. Done properly, a basement adds a whole storey of living space invisible from the street. Costs are genuinely bespoke, so we price basements after survey rather than from a table.
Flats and mansion blocks. A large share of NW3 lives in converted and purpose-built flats, where permitted development doesn't apply: schemes need full planning plus the freeholder's agreement. We confirm the position at your address before any design work.
Every street is different. That's the point.
We design to Hampstead'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 Hampstead in 2026
Realistic Hampstead build budgets occupy the bands below — high-standard labour and materials, with VAT, professional fees and kitchen fit-out additional:
| Extension type | Typical Hampstead cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £50,000 – £100,000 | 2–3 months | Full application in the conservation area |
| Single-storey rear | £90,000 – £180,000 | 3–5 months | Full application in the conservation area |
| Kitchen extension (incl. mid-range kitchen) | £100,000 – £200,000 | 3–5 months | Full application in the conservation area |
| Hip-to-gable loft + rear dormer | £80,000 – £140,000 | 8–12 weeks | Full application on most NW3 streets |
| Wrap-around extension | £110,000 – £220,000 | 4–6 months | Full application |
| Double-storey rear | £120,000 – £250,000 | 5–7 months | Full application |
| Garage conversion | £25,000 – £55,000 | 4–6 weeks | Depends on the street — we check |
Hampstead is the premium end of our patch: £3,500–£5,000+ per square metre is realistic — roughly 40–50% above the North London baseline — and listed-building and basement work runs higher still. The premium buys conservation-grade materials and detailing, glazing and finishes that match the houses, and the design time that planning here properly demands. Once we've made the free site visit, the price we give you is fixed and set out item by item.
Permissions, handled
Planning permission in Hampstead — assume it's needed, then plan for it
Start from the assumption that you'll need a full application. The vast Hampstead conservation area covers much of NW3, and within it permitted development rights are restricted; listed buildings need listed building consent on top, covering internal as well as external work. On streets where the standard rules do apply, the usual allowances hold — a 3m rear extension on semis and terraces or 4m on detached houses as of right, rising to 6m and 8m through larger-home prior approval, plus generous loft volumes — and we check your address against Camden's conservation map before anything else.
Timescales: Camden's benchmark for a standard householder decision is in the region of eight weeks. Listed building and basement schemes carry more preparation — heritage statements, impact assessments — so we build that into the programme honestly rather than promising miracles.
Basements: Camden's basement policy is strict and specific — a Basement Impact Assessment dealing with ground conditions, water and neighbouring structures is a requirement, not a nicety. We assemble the right engineering team from day one.
Party walls: terraces and close-packed houses make the Party Wall Act near-universal in NW3 — budget £1,000–£2,500 per affected neighbour if surveyors are appointed, with basement awards the most involved of all. We manage the whole process.
Our approach: where permitted development genuinely applies we'll secure a Lawful Development Certificate so the position is beyond argument; where full consent is needed — usually — we design for approval from the first drawing. In Hampstead, planning-heavy isn't a barrier. It's the service.
How it works
How it works
- Free site visit — we examine your Hampstead house together, verify its conservation and listed status, and tell you candidly what's feasible, what it costs and how consent will run.
- Design & drawings — drawings and 3D visuals crafted to survive Camden-level scrutiny while serving the way you actually live.
- Planning, handled — the entire Camden submission is ours to run — listed building consent and basement assessments included where needed — right through to the decision.
- Fixed-price build — delivered to conservation-grade standards by our vetted North London team, certified by building control and handed over without loose ends.
The whole-house brief in Hampstead
Plenty of Hampstead projects are not extensions at all so much as reinventions: a listed or conservation-constrained house rethought floor by floor, with a basement doing the quiet heavy lifting and a garden-side addition finishing the composition. At NW3 values that programme rewards real design, and it is priced as one fixed figure however far it runs.
We run that scale of work through our luxury extensions service, one team from heritage drawings to handover, with the budget bands laid out plainly in the luxury extension cost guide.
Our work
Recent work near Hampstead
From our build team's recent North London slate: a full house transformation taking a family home from 120m² to 360m², a 55m² garden room with kitchen and bathroom, and an Edwardian conversion in Finchley, a short hop north. Tell us what you're contemplating and we'll bring the most relevant examples to the site visit.
Questions, answered
Hampstead extension FAQs
What does a house extension cost in NW3?
More than anywhere else we work: £3,500–£5,000+ per square metre, with single-storey rears commonly £90,000–£180,000 and kitchen extensions £100,000–£200,000, excluding VAT and fees. Listed-building and basement projects run higher. Every figure we quote is fixed and itemised after a free site visit.
My house is in the Hampstead conservation area — is an extension realistic?
Genuinely, yes. Camden approved 31 residential schemes in the latest two-week window, including exactly this kind of work. Conservation status restricts permitted development and raises the design bar — it doesn't close the door. Schemes designed for that scrutiny from day one are the ones that pass.
What if the building is listed?
Then alterations need listed building consent as well as planning permission — and that covers internal changes, not just the visible ones. It adds preparation (heritage statements, careful detailing) rather than impossibility; listed building consents featured among Camden's latest approvals.
How do basement extensions work in Camden?
Under the strictest basement policy in London. You'll need a Basement Impact Assessment covering ground conditions, groundwater and the structural effect on neighbours before consent is granted. It's demanding and deliberate — and it's how NW3 homeowners add a full storey without changing the view from the street.
How long does consent take in NW3?
Around eight weeks for a standard householder application once validated. Listed building consent and basement schemes need more preparation up front, so the honest answer is: longer, planned for properly. We run surveys, assessments and design in parallel to protect the programme.
Is extending worth the planning effort in Hampstead?
Usually, emphatically yes. NW3 space is among the most valuable in the country, so well-designed extra metres repay their cost — and the planning effort is a known, manageable process rather than a lottery. We handle design, consents and build as one fixed-price package, so the effort is ours, not yours.
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
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Free site visit anywhere in Hampstead, 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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