Area guide · EN4–EN5
House Extensions in New Barnet (EN4 & EN5)
Planning a house extension in New Barnet? We design, gain planning permission and build extensions and loft conversions across New Barnet — from the Victorian grid around the station to the 1930s avenues that filled in around it. Building a single-storey rear here generally runs to £45,000–£90,000, decisions rest with Barnet Council, and the council's latest decisions for the area are listed below, each with its reference and consent route. Arrange a free site visit and we'll give you chapter and verse on what your particular street allows.
Planning in New Barnet
What Barnet Council has approved in New Barnet
Barnet publishes its planning decisions, so you can see what the council passes in New Barnet instead of guessing. New Barnet sits in Barnet's Barnet Vale ward, which runs from the streets around the station and Lyonsdown up to the edge of Hadley Common, with a strip of N20 around Friern Mount Drive at its southern end. The decisions below come from that ward.
Three consent routes run through Barnet's decisions, and it helps to know which is which. A lawful development certificate confirms that a loft or a modest rear extension is permitted development. A prior approval covers a single-storey rear deeper than the standard 3m or 4m, up to 6m on a semi or 8m on a detached house, and any prior approval card gives the depth and height the owner applied for. A householder application is the full test, used for side, front and two-storey work, and it is where most refusals come from, although a prior approval can be refused too.
Recent planning decisions around New Barnet
Extension, loft and basement applications decided in Barnet's Barnet Vale ward, 23 Sep 2025 to 22 Sep 2026.
The newest decisions in those wards
- ApprovedSep 2026
Greenhill Park, EN5
Single storey rear extension following demolition of the existing conservatory and roof alterations of the existing single storey rear…
26/2303/HSE · Barnet CouncilHouseholder application
- RefusedSep 2026
Cromer Road, EN5
Two storey rear extension with new decking area. New front porch. New PV panels to front and rear roof
26/2593/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
The Linkway, EN5
Roof extension involving hip to gable, rear dormer window, 2no. front facing rooflights and new side gable window
26/3142/192 · Barnet CouncilLawful development certificate
- ApprovedAug 2026
Longmore Avenue, EN5
Single storey rear extension with raised patio and associated privacy screens. Side and front extension and new front porch following the…
26/2300/HSE · Barnet CouncilHouseholder application
- ApprovedAug 2026
Grasvenor Avenue, EN5
Single storey rear extension with a proposed depth of 3.70 metres, maximum height of 3.00 metres and eaves height of 3.00 metres…
26/2040/PNH · Barnet CouncilPrior approval, larger home extension
- ApprovedAug 2026
King Edward Road, EN5
Single storey extension to rear of attached garage, enlargement of the existing roof from hip to a gable end and enlargement of the rear…
26/2723/192 · Barnet CouncilLawful development certificate
- ApprovedAug 2026
Clifford Road, EN5
Single storey rear extension following the demolition of existing canopy
26/2809/192 · Barnet CouncilLawful development certificate
- ApprovedAug 2026
Sherrards Way, EN5
Single storey rear extension with a proposed depth of 5.14m, maximum height of 3.33m and eaves height of 2.50m following the demolition of…
26/2343/PNH · Barnet CouncilPrior approval, larger home extension
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
New Barnet's housing stock — and what works on each
New Barnet is a railway suburb in the most literal sense — the Great Northern station arrived in 1850, decades before most of the streets — and the housing tells that story in layers.
The Victorian and Edwardian grid around the station. The first wave: bay-fronted terraces and villas on the streets closest to the line. The strongest moves are the side-return extension (£35,000–£65,000), turning the alley beside the kitchen into one wide kitchen-diner, the single-storey rear (£45,000–£90,000), and the two combined as a wrap-around (£70,000–£140,000). Victorian roof shapes vary, so loft feasibility is street-by-street — we check pitch and ridge height before promising anything.
The 1930s infill avenues. Between and beyond the Victorian grid came the hipped-roof semis — and this is hip-to-gable country. A hip-to-gable loft with rear dormer (£55,000–£90,000) typically adds a double bedroom and en-suite, with front rooflights keeping the street elevation tidy, and on an unextended semi it can usually be confirmed as lawful development rather than argued through a full application.
Gardens with room to spare. New Barnet's plots often run long, which makes the garden building a natural option: a home office, gym or studio at the end of the garden. Garden rooms have their own permitted development allowance (single-storey, with height limits near boundaries), making them a quick route to serious extra space.
The larger homes towards the EN5 side. West towards High Barnet, plots and houses grow — supporting double-storey rears (£75,000–£160,000) and substantial side schemes for families planning to stay put for the long haul.
The streets by Hadley Common. At the ward's northern edge, Latimer Road, The Crescent and parts of Clifford Road fall inside the Monken Hadley conservation area, which takes in the common and some of the streets at its edge. Houses there lose the larger home prior approval route and the right to add a roof extension without planning permission, and side extensions always need consent. A few hundred metres south, the same kind of house has the full permitted development allowance, so the address decides the route.
Every street is different. That's the point.
We design to New 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 estimateHonest numbers
What a house extension costs in New Barnet in 2026
Realistic New Barnet build budgets look like this — decent-spec labour and materials, with VAT, professional fees and the kitchen itself costed on top:
| Extension type | Typical New Barnet cost | 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 |
Pricing here tracks the usual North London band of £2,800–£4,200 per square metre — multiply that out and a typical 20m² rear scheme needs a build budget running from the mid-£50,000s to the mid-£80,000s. Garden rooms price by specification, from simple insulated shells to fully plumbed studios. The quote you receive after the free site visit is fixed and itemised down to the line.
Permissions, handled
Planning permission in New Barnet — what you need to know
The permitted development routes work hard here. A semi or terraced house gets 3m of single-storey rear extension as of right and a detached house 4m — and with prior approval through the larger home extension scheme, those depths double to 6m and 8m. Lofts carry a generous volume allowance, which is how many New Barnet hip-to-gables go through as lawful development, and garden buildings have an allowance of their own.
Note the phrase "lawful development" on the certificate cards above: each one is an owner getting formal confirmation that the work needed no planning permission. That's a Lawful Development Certificate, and we recommend one for every PD project we build — it costs little, and it's the piece of paper that satisfies solicitors and surveyors when you sell or remortgage.
Full applications are needed for wrap-arounds, double-storey rears, flats, and homes where PD rights are already spent. For a standard householder application, Barnet's turnaround typically runs to about eight weeks.
Party walls: with terraces around the station and semis everywhere else, the Party Wall Act touches most New Barnet projects — budget £1,000–£2,500 per affected neighbour if surveyors are appointed. We prepare and serve the notices as part of the job, and we check your address against the council's conservation map before design starts. For the wider picture across Barnet, Enfield and Haringey, see our guide to extending in North London.
How it works
How it works
- Free site visit — we come out to your New Barnet home, talk through the brief, and give you an unvarnished view of feasibility, budget and the right consent route.
- Design & drawings — measured plans and 3D visuals built around the house you have and the life you want in it.
- Planning, handled — whether it's a full submission to Barnet Council or certifying the lawful development route, we run the paperwork all the way to decision.
- Fixed-price build — delivery by our proven North London team, signed off by building control and handed over tidy.
Our work
Recent work near New Barnet
New Barnet owners can read up on a recent job by our build crew, the Hadley Wood house extension: a full house transformation in Hadley Wood, taking a family home from 120m² to 360m². Raise your own plans at the site visit and we'll talk you through what a project like that involves.
Questions, answered
New Barnet extension FAQs
How much should I set aside for an extension in New Barnet?
Build costs sit at standard North London rates of roughly £2,800–£4,200/m² — so £45,000–£90,000 for a single-storey rear, £55,000–£90,000 for a hip-to-gable loft, £35,000–£65,000 for a side-return on the Victorian terraces. VAT and professional fees are on top; our quotes are fixed and itemised.
Do I need planning permission for a garden room or office in New Barnet?
Often not — outbuildings have their own permitted development allowance, provided the building stays single-storey, keeps within the height limits near boundaries and covers no more than half the garden. Inside the Monken Hadley conservation area the rules are tighter, and all of it matters, so we confirm your plot's position before designing.
What loft conversion suits my hipped-roof semi?
Usually hip-to-gable with a rear dormer and front rooflights. It's the template for New Barnet's 1930s semis — typically a double bedroom plus en-suite, usually achievable as lawful development under the loft volume allowance, unless the house is in the conservation area by Hadley Common.
Is a Lawful Development Certificate worth the bother if I don't need permission?
Emphatically yes. We obtain them as standard: the certificate proves your extension was lawful on the day it was built, which is exactly what a buyer's solicitor will demand years later. Skipping it saves pennies and risks pounds.
What works best on the Victorian terraces near the station?
A side-return extension, a rear extension, or both together as a wrap-around — these terraces were built with narrow back kitchens that open-plan living has outgrown. Party wall agreements with both neighbours are usually part of the package; we manage them.
How long does the whole process take in New Barnet?
Roughly: a few weeks for survey and design, around eight weeks for a Barnet householder decision (lawful development certificates are often quicker), then two to four months on site for single-storey work — longer for two-storey schemes. We give real programme dates with the quote.
What we build in New Barnet
The same team designs, gets planning and builds — one fixed, itemised price whichever route your New Barnet project takes.
- Kitchen extensions in New Barnet
- Side return extensions in New Barnet
- Double-storey & wrap-around in New Barnet
- Loft conversions in New Barnet
- Orangeries in New Barnet
- Garden rooms & offices in New Barnet
Checking the rules for New Barnet first?
Nearby areas we cover
What clients say
Rated 5.0 on Google
“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.”
“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.”
“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.”
“Really pleased with the work from The Extension Company. We had our extension done in Hampstead and the whole experience was excellent. Great communication from start to finish, The quality of the finish is excellent and we’re really happy with the result. Would definitely recommend them if you’re thinking about an extension.”
Reviews shown word for word from our Google profile. See 9 more client reviews · Read all 16 reviews on Google
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