Area guide · N2
House Extensions in East Finchley (N2)
Planning a house extension in East Finchley? We design, gain planning permission and build extensions and loft conversions across N2 — from the terraces around the High Road and Cherry Tree Wood to the Hampstead Garden Suburb fringe. Most single-storey rear extensions here cost £45,000–£110,000 to build, applications go to Barnet Council, and the most-approved scheme type in N2 right now is the single-storey rear extension — seven N2 approvals landed in the latest decision window. Start with the free site visit — we'll give you an honest read on what your side of N2 allows.
Live planning data
What Barnet Council is actually approving in East Finchley right now
We record every residential planning decision across North London, which lets you trade guesswork about Barnet for evidence. Seven N2 schemes won approval in the most recent decision period; here are three that show the range:
- 8 Aylmer Road, N2 — single-storey rear extension, 4.0m deep, granted via the prior approval route (approved)
- 30 Summerlee Avenue, N2 — single-storey rear extension with two rooflights (approved)
- 20 Holne Chase, N2 — garage conversion to habitable space (approved)
Across all of Barnet, 63 residential schemes won approval in that same fortnight — the busiest pipeline in our patch.
What the data says: rear extensions dominate N2, and the Aylmer Road consent is the teaching point. Standard permitted development caps a rear extension at 3m deep on semis and terraces (4m on detached homes) — but the larger home extension scheme stretches that to 6m (8m detached) with prior approval, and that's how a 4.0m-deep extension went through here without a full application. Holne Chase shows the other end of the spectrum: the garage conversion — pound for pound, the cheapest extra room in the book.
All three examples sit on Barnet Council's public register of decisions. They're not our builds — they're evidence of the borough's current appetite — and every application is determined on its own merits.
Local knowledge
East Finchley's housing stock — and what works on each
East Finchley has the widest market spread of any area we cover — sensible terrace money at one end, some of the most expensive residential streets in the country at the other.
The terraces around the High Road and Cherry Tree Wood. Victorian and Edwardian terraces — the engine room of N2. The side-return extension (£35,000–£80,000) creates the full-width kitchen-diner; the loft conversion with rear dormer (£55,000–£110,000) adds the bedroom and en-suite; and as the approvals show, the single-storey rear (£45,000–£110,000) is the most-travelled route of all.
The Hampstead Garden Suburb fringe (south-west). Among the most carefully protected suburban streets in Britain — conservation area, restricted permitted development rights and exacting design expectations. Extensions happen here, but they're designed to Suburb standards from the first sketch, not adapted afterwards.
The Bishops Avenue corridor. Serious money: large detached houses on generous plots where double-storey rears (£75,000–£190,000) and full wrap-arounds (£70,000–£170,000) make sense — with specification, security and project management to match.
The interwar streets on the N2 fringes. Hipped-roof 1930s semis — natural territory for the hip-to-gable loft conversion, which happens to be the most-approved scheme type across the borough as a whole.
Every street is different. That's the point.
We design to East Finchley'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 East Finchley in 2026
The honest answer in N2 is "it depends which street". Most of East Finchley builds at North London baseline rates; the premium pockets towards the Suburb fringe and the Bishops Avenue corridor run up to 20% over. Realistic all-in build ranges follow — exclusive of VAT, professional fees and kitchen fit-out:
| Extension type | Typical East Finchley cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £35,000 – £80,000 | 2–3 months | Often permitted development |
| Single-storey rear | £45,000 – £110,000 | 3–4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £55,000 – £130,000 | 3–4 months | Often permitted development |
| Loft conversion + rear dormer | £55,000 – £110,000 | 6–10 weeks | Usually permitted development |
| Wrap-around extension | £70,000 – £170,000 | 4–6 months | Full application |
| Double-storey rear | £75,000 – £190,000 | 5–7 months | Full application |
| Garage conversion | £18,000 – £42,000 | 4–6 weeks | Usually permitted development |
Expect £2,800–£5,000 per square metre in East Finchley — the standard £2,800–£4,200 North London baseline on most streets, pushed past on the premium ones where detailing and spec rise to meet the postcode. Scale it up and a 25m² family kitchen-diner spans £70,000–£125,000, street depending. Costs are confirmed in a fixed, itemised quote once we've visited — and fixed means fixed: the agreed total is the invoiced total.
Permissions, handled
Planning permission in East Finchley — what you need to know
The bulk of N2 extensions go ahead without a full planning application. Semis and terraces carry a 3m rear-extension allowance under permitted development, detached homes 4m — and the larger home extension scheme unlocks 6m and 8m via prior approval, which is precisely how the 4.0m-deep extension at Aylmer Road was granted. Lofts have their own generous volume allowance.
Where permission is still required: double-storey and wrap-around schemes, flats, and anything on the Hampstead Garden Suburb fringe, where the conservation area restricts permitted development rights and design scrutiny is rightly high. Elsewhere, we check your address against the council's conservation map as part of the free consultation.
Barnet householder decisions land in roughly eight weeks as a rule, with prior approval and lawful development routes often faster. Semis and terraces mean party walls: budget £1,000–£2,500 per affected neighbour if surveyors are appointed — we prepare the notices as part of the job. And wherever your project proceeds under permitted development, we obtain a Lawful Development Certificate, so the works are unimpeachable when you sell.
How it works
How it works
- Free site visit — we walk your N2 property, High Road terrace or Suburb-fringe semi, and advise plainly on feasibility, spend and the route through planning.
- Design & drawings — thorough plans and 3D visuals designed around your home and your family's day-to-day.
- Planning, handled — the complete application prepared and submitted to Barnet Council, with us managing it to decision.
- Fixed-price build — our vetted North London builders deliver it, building control signs it off, and you get a neat handover.
Our work
Recent work near East Finchley
Recent projects from the build team include 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 neighbouring Finchley — a few minutes up the road. Raise it at your visit and we'll show the past projects most akin to yours.
Questions, answered
East Finchley extension FAQs
How deep can my rear extension go in East Finchley without full planning?
Up to 3m on a semi or terrace (4m detached) under standard permitted development — and up to 6m (8m detached) via the larger home extension prior approval route. The recent 4.0m-deep approval at Aylmer Road went through exactly this way.
Can houses on the Hampstead Garden Suburb fringe be extended?
Yes, but on the Suburb's terms: the conservation area restricts permitted development, so expect a full application and some of the most exacting design scrutiny in London. Schemes succeed when they're conceived to that standard from the start — that's how we design them.
Why do East Finchley extension quotes vary so much street to street?
Because N2 spans two markets. Terraces near the High Road build at baseline North London rates; the premium streets towards the Suburb fringe and the Bishops Avenue corridor carry up to 20% more in detailing, spec and site logistics. Same borough, different briefs.
Is a garage conversion a smart move in N2?
Often the smartest pound-for-pound: £18,000–£42,000 for a new habitable room with no garden lost, and usually no full application needed. The recent approval at Holne Chase — a garage converted to living space — shows Barnet passing exactly this scheme.
What's Barnet's current decision speed?
Around eight weeks for a standard householder application, with prior approval routes often quicker. The pipeline is healthy: 63 residential approvals borough-wide in the latest fortnight, seven of them in N2.
What suits a terrace near Cherry Tree Wood?
The classic pairing: a side-return or rear extension for the kitchen-diner, and a dormer loft for the extra bedroom. Two of the latest N2 approvals — Summerlee Avenue's rear extension with rooflights among them — are this playbook in action.
Nearby areas we cover
Ready to see what's possible on your street?
Free site visit anywhere in East Finchley, honest feasibility advice and a fixed, itemised price — design, planning and build handled end to end.
Or call us — 020 3051 9430