Area guide · EN5
House Extensions in Arkley (EN5)
Planning a house extension in Arkley? We design, gain planning permission and build large extensions on the green-belt ridge west of Barnet, where the plots are the biggest in the borough and the projects match. The average Arkley sale over the last year was £883,000, with detached homes averaging £1.31 million (Rightmove, July 2026), and the schemes that suit these houses are substantial: double-storey reworks, wrap-arounds and whole-house transformations. The one thing every Arkley project has to respect is the green belt, and that is exactly the territory we work in. A free design visit settles the two questions that matter: what your plot can carry, and which planning route gets it approved.
Live planning data
What Barnet Council is actually approving right now
Arkley sits wholly inside the London Borough of Barnet, so every application here is judged against Barnet policy. The approvals weather is steady: in the latest EN5 pull from Barnet's published planning register, the schemes clearing were single-storey rear extensions, garden buildings and annexes, and loft conversions with rear dormers. The staples work here just as they do in Barnet proper.
Arkley briefs tend to run bigger than the postcode's bread and butter, though. On plots this size the conversation is usually a wide glazed rear, a double-storey rework, or an extension plus full internal reconfiguration, and at that scale the green belt becomes the deciding layer. Barnet does approve substantial schemes in the green belt; what it refuses are additions that read as disproportionate against the original house. Winning consent is a design job: proportion, siting, materials and a case made in the language of the policy.
Source: the published planning register of Barnet Council. The numbers describe the local approvals weather, not our own project list, and any individual application is decided on its own specific merits.
Local knowledge
Arkley's housing stock, lane by lane
Arkley is a village-shaped strip of serious houses along Barnet Road and the lanes running off it, with the green belt on every side. There are three broad generations of house, and each takes a different playbook.
The Barnet Road frontage and the classic lanes. Along Galley Lane, Glebe Lane and Barnet Gate Lane, substantial detached homes sit well back on deep plots behind hedges and gates. Depth is the asset: a large glazed single-storey rear (£50,000 to £110,000) or a wrap-around (£85,000 to £170,000) fits without ever feeling tight, and the long gardens keep the extension invisible from the lane, which planners like.
The inter-war houses and bungalows. Arkley has a generation of 1920s and 1930s houses, including detached bungalows on plots that dwarf them. These are the village's biggest opportunities: a double-storey rework (£90,000 to £200,000) or a full first-floor addition can double the accommodation, subject to the green belt proportion test against the original building. This is precisely the calculation we model before drawing anything.
The modern rebuilds. Plenty of Arkley homes are already generous replacement houses, on Rowley Lane, Hendon Wood Lane and the private roads. Here the brief is usually reconfiguration plus extension: a basement leisure floor, a kitchen-garden wing, or a whole-house remodel that makes the existing volume work harder. They are exactly the projects our luxury extensions service is built around.
Every street is different. That's the point.
We design to Arkley'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 Arkley in 2026
Arkley build costs sit 20 to 30 percent above the North London baseline. The houses are large, the specification expected here is high, and green-belt sites often carry extra design and groundworks care. Realistic all-in build ranges, excluding VAT, professional fees and kitchen fit-out:
| Extension type | Typical Arkley cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £45,000 to £80,000 | 2 to 3 months | Often permitted development |
| Single-storey rear | £50,000 to £110,000 | 3 to 4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £65,000 to £130,000 | 3 to 4 months | Often permitted development |
| Hip-to-gable loft + rear dormer | £65,000 to £110,000 | 6 to 10 weeks | Usually permitted development |
| Wrap-around extension | £85,000 to £170,000 | 4 to 6 months | Full application |
| Double-storey rear | £90,000 to £200,000 | 5 to 7 months | Full application |
| Garage conversion | £25,000 to £45,000 | 4 to 6 weeks | Usually permitted development |
Expect £3,200 to £5,000 per square metre against the wider North London range of £2,800 to £4,200. Larger programmes are banded honestly in our luxury extension cost guide: the banding flexes to whatever your plot and brief actually need. Our pricing works the old-fashioned way: a free design visit first, then a fixed quote itemised line by line, and that sum is what you actually hand over.
Permissions, handled
Planning permission in Arkley: the green belt, plainly
The green belt is the layer that matters. Most of Arkley sits within Barnet's green belt. That does not mean you cannot extend; it means an extension must not amount to a disproportionate addition over the original building (the house as first built, not as you bought it). Where a house has already been extended, the remaining headroom shrinks, so we always establish the original-building baseline first.
Permitted development still applies in the green belt. Unlike some designations, green belt status does not strip PD rights. A detached house can take a 4m single-storey rear extension without an application, or up to 8m under larger-home prior approval with neighbour consultation, and generous loft allowances usually survive too. For anything built under PD we secure a Lawful Development Certificate, so the position is documented when you sell. We cover the tactics in detail in our guide to extending in the green belt.
Bigger schemes go to full application. Double-storey rears, wrap-arounds and basements are judged on design quality and on the proportion case. A householder application takes roughly eight weeks to determine. Basements are a quietly effective route here: floor area below ground changes how the proportion argument reads, and the house presents to the lane exactly as before.
Party walls and boundaries. Detached plots make formal awards less common, but excavation near a boundary can still trigger the Party Wall Act. Where surveyors are appointed, budget £1,000 to £2,500 per affected neighbour. We manage the notices as standard.
How it works
How it works
- Free design visit. We walk your Arkley plot, establish the original-building baseline and the green belt position, and talk frankly about feasibility, budget and route.
- Design and drawings. A drawing set and 3D imagery pitched at the level this market expects, composed to make the proportion case for you.
- Planning, handled. The full submission goes to Barnet under our management, and we shepherd it through to the decision notice.
- Fixed-price build. Built by the North London team we trust with our name, closed out with building control sign-off and an immaculate handover.
Questions, answered
Arkley extension FAQs
Can I extend a house in the Arkley green belt?
Yes, in most cases. Green belt policy allows extensions provided they are not disproportionate additions over the original building, meaning the house as first built. The judgement is about scale and design rather than a flat ban, and permitted development rights usually still apply. We establish your original-building baseline and remaining headroom before any design work begins.
What should I expect to pay for an Arkley extension?
Plan on £3,200 to £5,000 per square metre, roughly 20 to 30 percent above the North London norm, reflecting plot sizes and specification. A glazed single-storey rear typically runs £50,000 to £110,000 and double-storey schemes £90,000 to £200,000, excluding VAT and fees. You receive a fixed, itemised quote after a free visit.
Does Arkley fall under Barnet Council?
Yes. Arkley sits wholly within the London Borough of Barnet, so Barnet policy decides every application, including the green belt proportion test. A standard householder application takes roughly eight weeks to determine.
My house has already been extended. Can I still add more?
Sometimes, and the answer depends on arithmetic as much as design. The green belt test measures all additions against the original building combined, so earlier extensions use up headroom. Basements and outbuildings can change the equation. We calculate the position exactly at the design visit.
Is a basement realistic in Arkley?
Frequently, yes. On large green-belt plots a basement adds serious floor area while keeping the house's presence at the lane unchanged, which helps both the planning case and the street. Basements are full-application projects with proper engineering behind them, and party wall procedures where excavation nears a boundary.
How long will my project take?
Allow a few weeks for survey and design, around eight weeks for a council decision once submitted, and an on-site period from three or four months for a single-storey scheme to seven for a double-storey rework. We give honest programme dates with the quote.
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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”
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