Area guide · EN5 & EN4
House Extensions in Barnet (EN5 & EN4)
Planning a house extension in Barnet? We design, gain planning permission and build extensions and loft conversions across High Barnet, East Barnet and New Barnet. A single-storey rear extension here typically costs £45,000–£90,000 to build, many can go ahead under permitted development without a full application to Barnet Council, and the hipped roofs on Barnet's 1930s semis are made for a hip-to-gable loft conversion. Book a free site visit and we'll tell you exactly what's possible on your street.
Planning in Barnet
What Barnet Council has recently approved
Barnet Council publishes its planning decisions, so you don't have to guess what it will accept or turn down. The records below come from the two council wards that cover the town itself: High Barnet, which takes in the town centre, Hadley Green, Monken Hadley and Arkley, and Underhill, the streets around Mays Lane. New Barnet and East Barnet have their own wards, and their decisions sit on their own pages.
Read each card for the route as well as the outcome. A hip-to-gable loft with a rear dormer can go through as a lawful development certificate, which only asks whether the work is permitted development. A side or wrap-around extension goes in as a householder application, where the council weighs how it sits on the street and against the neighbours. Refusals count as much as approvals because they show where Barnet draws its lines, and for work like this the route turns on depth, height and position, so we settle it before any detailed drawing starts.
Recent planning decisions around Barnet
Extension, loft and basement applications decided in Barnet's High Barnet and Underhill wards, 23 Sep 2025 to 22 Sep 2026.
The newest decisions in those wards
- ApprovedSep 2026
Alston Road, EN5
Single storey wraparound extension with rooflights, new internal courtyard and extension to the existing patio area following removal of…
26/2743/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Fitzjohn Avenue, EN5
Roof extension including hip to gable, rear dormer window, 2no. rear and 3no. front facing rooflights and raising the ridge height
26/2946/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Old Fold View, EN5
Single storey rear extension with 3no rooflights. Removal of side window and chimney stack.
26/3010/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Normandy Avenue, EN5
Part single, part two storey side/rear extension with 3no. rooflights, raised decking area with glass balustrade following demolition of…
26/2622/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Queens Road, EN5
Roof extension involving hip to gable, rear dormer window, 3no. front and 1no. side facing rooflights and new side gable window and…
26/3186/192 · Barnet CouncilLawful development certificate
- ApprovedSep 2026
Snowberry Close, EN5
Single storey rear extension with 2no. rooflights, new retaining wall and alterations to existing patio area
26/2668/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Barnet Road, EN5
Conversion of existing integral garage to habitable room, insertion of windows to replace garage doors. New front detached double garage…
25/3540/HSE · Barnet CouncilHouseholder application
- RefusedSep 2026
Cavendish Road, EN5
Single storey side and rear wraparound extension with 4no. rooflights following demolition of existing garage and conservatory. Single…
26/2727/HSE · Barnet CouncilHouseholder application
Look a reference up on the council’s own register: Barnet Council planning search.
Source: GLA Planning London Datahub, 23 Sep 2025 – 22 Sep 2026. Data updated September 2026. This list last changed 23 September 2026. The datahub can lag a council’s own register by a few weeks.
These are council decisions on applications in these wards, shown as local planning context. They are not necessarily projects undertaken by us, and they are not our approval rate. Planning outcomes depend on your specific property and proposal.
Local knowledge
Barnet's housing stock — and what works on each
Barnet isn't one market; it's three or four, and the right extension depends on which street you're on.
The 1930s semi belt (East Barnet, New Barnet, Oakleigh Park, parts of EN5). This is classic Metroland: bay-fronted, hipped-roof semis with decent gardens and side passages. Two moves do the heavy lifting here. The hip-to-gable loft with rear dormer converts the wasted hip into a full double bedroom and en-suite, typically £55,000–£90,000, and our Barnet loft conversion guide matches loft types to the town's rooftops. The single-storey rear extension opens the kitchen into the garden, typically £45,000–£90,000 depending on size and spec.
Victorian and Edwardian terraces (High Barnet, around Wood Street and the High Street). Narrower plots with rear additions — the play here is the side-return extension (£35,000–£65,000), reclaiming the dead alley beside the kitchen to create a full-width kitchen-diner, often combined with a rear extension as a wrap-around. Party wall agreements with both neighbours are usually needed; we manage that process.
Detached and semi-rural Barnet (Arkley, Hadley, the green-belt edge). Bigger plots take double-storey rear extensions (£75,000–£160,000) and substantial wrap-arounds. Some of this edge sits in the green belt, where volume limits bite — we check before you fall in love with a scheme.
Monken Hadley and the conservation streets. Monken Hadley and Wood Street are conservation areas, covering the historic houses around Hadley Green and along Wood Street. Permitted development rights are restricted, materials matter, and rooflights and dormers are scrutinised. Both areas also carry Article 4 directions, and on the parts of each area they cover, even extending the house needs a planning application. Extensions absolutely still happen here; they just need conservation-literate design. That's a service, not a problem.
Every street is different. That's the point.
We design to Barnet'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 estimateKitchen extensions in Barnet
Where the kitchen sits in a Barnet house decides how you extend it. On the 1930s semis of East Barnet, New Barnet and Oakleigh Park it is usually at the back, beside the side passage, so a single-storey rear extension can join kitchen and dining room into one room facing the garden. Permitted development allows 3m on a semi, and the prior-approval route takes that to 6m where the garden is deep enough to spare it. High Barnet's Victorian and Edwardian terraces keep the kitchen in a narrow rear addition, so the extra width comes from infilling the side return, or from wrapping round the back as well, which usually means a full application. In the Wood Street and Monken Hadley conservation areas the 6m prior-approval route isn't available, and anything built out beyond a side wall needs planning permission, which catches a typical side return. To see how Barnet treats these schemes in practice, look up its single-storey rear and wrap-around decisions for the High Barnet and Underhill wards, starting with the records above. Our kitchen extensions page covers layouts, glazing and fit-out.
Honest numbers
What a house extension costs in Barnet in 2026
These are the North London baseline ranges, and they apply across Barnet — labour and materials to a good standard, excluding VAT, professional fees and kitchen fit-out:
| Extension type | North London baseline costs (apply across EN5 & EN4) | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £35,000 – £65,000 | 2–3 months | Often permitted development |
| Single-storey rear | £45,000 – £90,000 | 3–4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £55,000 – £110,000 | 3–4 months | Often permitted development |
| Hip-to-gable loft + rear dormer | £55,000 – £90,000 | 6–10 weeks | Usually permitted development |
| Wrap-around extension | £70,000 – £140,000 | 4–6 months | Full application |
| Double-storey rear | £75,000 – £160,000 | 5–7 months | Full application |
| Garage conversion | £18,000 – £35,000 | 4–6 weeks | Usually permitted development |
As a rule of thumb, Barnet build costs run £2,800–£4,200 per square metre, the North London baseline, driven by London labour and the care period properties need. We quote fixed, itemised prices after a free site visit, so the number you sign is the number you pay.
Permissions, handled
Planning permission in Barnet — what you need to know
Many Barnet extensions don't need a full planning application. Permitted development covers single-storey rear extensions up to 3m deep on semis and terraces (4m on detached homes), and up to 6m/8m under the larger home extension scheme with prior approval. Loft conversions have a separate volume allowance, which is why a hip-to-gable with rear dormer on a semi can often go ahead as lawful development.
Where you do need permission: double-storey and wrap-around extensions, side extensions and larger rear extensions in the conservation areas (Monken Hadley, Wood Street and others), flats and maisonettes, and homes where previous owners have already used up permitted development rights. Barnet aims to decide standard householder applications in around eight weeks.
Party walls: on a semi or a terrace the Party Wall Act usually applies — budget £1,000–£2,500 per affected neighbour if surveyors are appointed, and start the conversation early. We prepare the notices as part of the job.
Our approach: we design to what Barnet Council's published decisions show it approving and refusing, starting with the ward records above. Where a Lawful Development Certificate is the smarter route, we'll tell you and obtain it, so your extension is bulletproof when you sell.
Across the London Borough of Barnet
Barnet the town is one corner of a large borough. Cross it and the postcode changes, sometimes the council does too, and so do the designations that shape what you can build. What to know in each area, with our guide to each (for Enfield and Haringey too, start with our North London extensions guide):
- Monken Hadley, EN5: the Monken Hadley conservation area around Hadley Green reaches into the green belt.
- Arkley, EN5: much of it is green belt, where Barnet weighs an extension against the size of the original house.
- New Barnet straddles EN4 and EN5; whichever your postcode, the application still goes to Barnet.
- East Barnet, EN4: Barnet decides here, although the EN4 postcode also runs into Enfield and Hertsmere.
- Totteridge, N20: its conservation area overlaps the green belt, which shapes both the size and the look of an extension.
- Whetstone shares N20 with Totteridge, so an N20 address alone won't tell you whether the Totteridge conservation area applies.
- Friern Barnet, N11: Barnet's side of a postcode that also reaches into Enfield and Haringey.
- North Finchley, N12: wholly within Barnet, with the Moss Hall Crescent conservation area inside the postcode.
- Finchley, N3: the Finchley Church End and Finchley Garden Village conservation areas restrict permitted development on the streets they cover.
- East Finchley, N2: Barnet decides, though N2 is shared with Haringey, and part of the postcode lies inside the Hampstead Garden Suburb conservation area.
- Hampstead Garden Suburb, NW11: a conservation area where the Hampstead Garden Suburb Trust has to consent as well as Barnet.
- Golders Green, NW11: Barnet planning, a Golders Green conservation area of its own, and Trust consent on the Suburb side of the postcode.
- Hendon, NW4: Hendon Church End and Hendon The Burroughs are both conservation areas.
- Mill Hill, NW7: the Mill Hill conservation area around the old village takes in green-belt land.
- Edgware, HA8: Barnet decides east of the High Street, but HA8 also crosses into Harrow and Brent, so the address settles which council you apply to.
- Hadley Wood, EN4: Enfield, not Barnet, decides Hadley Wood's applications, and its conservation area is an Enfield designation. Barnet's side starts at the western end of Camlet Way, inside the Monken Hadley conservation area.
How it works
How it works
- Free site visit — we walk your Barnet property, talk through what you want, and give honest guidance on feasibility, cost and the planning route.
- Design & drawings — detailed plans and 3D visuals tailored to your house and how you live.
- Planning, handled — we prepare and submit everything to Barnet Council and manage it to decision.
- Fixed-price build — our own team at Pine Grove Design & Build carries out the work, through to building control sign-off and a tidy handover.
Our work
Recent work near Barnet
One recent project is next door in Hadley Wood: a full house transformation that took a family home from 120m² to 360m². The Hadley Wood case study has the photos. Ask at your Barnet site visit and we'll talk you through the parts that match your plans.
Questions, answered
Barnet extension FAQs
How much does a house extension cost in Barnet?
Typically £45,000–£90,000 for a single-storey rear extension build, £55,000–£90,000 for a hip-to-gable loft, and £75,000+ for double-storey schemes — excluding VAT and fees. Barnet sits on North London rates of roughly £2,800–£4,200/m². We give a fixed, itemised quote after a free site visit.
Do I need planning permission for an extension in Barnet?
Often not — standard rear extensions and many loft conversions proceed under permitted development, ideally backed by a Lawful Development Certificate. You will need permission for two-storey schemes, wrap-arounds, and side or larger rear extensions in conservation areas like Monken Hadley or Wood Street.
How long does Barnet Council take to decide?
Around 8 weeks for a standard householder application once validated. Design and drawings before that typically take 4–8 weeks; lawful development certificates are usually quicker.
What suits a 1930s semi in East Barnet or New Barnet?
Usually a hip-to-gable loft conversion with rear dormer, which puts a double bedroom and en-suite in the roof, a single-storey rear extension for an open-plan kitchen-diner, or both phased together. The hipped roof is what makes the loft work; the garden depth is what makes the rear extension work.
Do you cover all of Barnet?
Yes — High Barnet, Chipping Barnet, East Barnet, New Barnet, Oakleigh Park, Arkley, Monken Hadley and the Hadley Wood border, plus neighbouring Whetstone, Totteridge and Cockfosters.
Is my house in a conservation area?
Barnet has a number of conservation areas, including Monken Hadley and Wood Street around the town, and Totteridge, Mill Hill and Hampstead Garden Suburb further across the borough. We check your address against the council's conservation map as part of the free consultation, before any design work starts.
What we build in Barnet
The same team designs, gets planning and builds — one fixed, itemised price whichever route your Barnet project takes.
Nearby areas we cover
What clients say
Rated 5.0 on Google
Including three reviews from clients in Barnet.
“From the initial site visit onwards to my property in Barnet, we felt that the team actually listened to what we wanted. They suggested a few changes to the layout that we hadn't considered, and those changes have made a huge difference. Would definitely use again and recommend”
“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. The hip-to-gable and rear dormer gave us a big double bedroom with an en-suite. Tidy, professional and finished on schedule. Would recommend to anyone in North London thinking about a loft conversion.”
“Excellent experience with The Extension Company. They completed our loft conversion and delivered exactly what they promised. The new bedroom and en-suite have added valuable space to our property in Barnet, the quality of the workmanship is first class. The team were friendly, knowledgeable and always happy to answer questions throughout the build.”
“The Extension Company built a 5m single storey rear extension on our Victorian terrace in Crouch End. Went down the permitted development route so no planning application needed, which they explained up front and saved us months. Kitchen-diner now opens onto the garden with sliding doors. £87k all in, matched the quote.”
“We had been putting off our loft conversion for years because the whole process felt overwhelming. The team made it much easier than expected and handled the drawings, planning and build for us. We now have a lovely extra bedroom and shower room.”
“Our wrap-around extension has completely transformed the ground floor. We now have the open plan kitchen and family space we wanted without losing all of the garden. Thanks to everyone involved.”
Reviews shown word for word from our Google profile. See 9 more client reviews · Read all 16 reviews on Google
Free site visit
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