Area guide · N11
House Extensions in Friern Barnet (N11)
Planning a house extension in Friern Barnet? From the 1930s semis along Friern Barnet Lane and around the village green to the Edwardian terraces towards New Southgate, N11 is covered end to end by our design, planning and build service. Two numbers frame most projects here: £45,000–£90,000 to build a typical single-storey rear, and, in Friern Barnet itself, one council — Barnet — making the call. Better still, hip-to-gable loft conversions and single-storey rears — the two staple schemes on Barnet's 1930s streets — are tailor-made for Friern Barnet's housing. The free site visit comes first; that's where we tell you what your own street will carry.
Planning in Friern Barnet
What Barnet Council approves on houses like Friern Barnet's
Guesswork is a poor way to start an extension, which is why we read Barnet's published decisions before we draw. The dated list on this page is Barnet's Friern Barnet ward, refusals included, and it covers more than the N11 streets around the village green. The ward runs south into the N10 roads on Barnet's side of the Muswell Hill border and north into N20 on the Whetstone side, so all three postcodes turn up in it.
On the hipped-roof semis along Friern Barnet Lane, the two schemes to look for are the hip-to-gable loft with a rear dormer and the single-storey rear. On the terraced streets the roof work changes shape: a dormer over the main roof, sometimes with a second over the back addition. Each decision shows the route it took, and the refusals are the useful ones to read, because they show where Barnet drew the line on a house like yours.
Recent planning decisions around Friern Barnet
Extension, loft and basement applications decided in Barnet's Friern Barnet ward, 23 Sep 2025 to 22 Sep 2026.
The newest decisions in those wards
- ApprovedSep 2026
Hampden Road, N10
First floor rear extension including Juliette balcony. New rear rooflight window. Replacement of pitched roof over ground floor projection…
26/1718/HSE · Barnet CouncilHouseholder application
- RefusedSep 2026
Earl Close, N11
Single storey rear extension. New front door following removal of window. Erection of a rear shed
26/2580/HSE · Barnet CouncilHouseholder application
- RefusedSep 2026
Gresham Avenue, N20
Two storey side extension, single storey rear extension and extension and lowering of existing basement. New raised rear terrace…
26/2265/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
George Crescent, N10
Single storey rear extension with a proposed depth of 4.00 metres, maximum height of 4.00 metres and eaves height of 3.00 metres following…
26/2881/PNH · Barnet CouncilPrior approval, larger home extension
- ApprovedAug 2026
St Johns Avenue, N11
Roof extension with 1no. rear dormer window over main roof and 1no. rear dormer over outrigger roof, 3no. front facing rooflights and new…
26/3067/192 · Barnet CouncilLawful development certificate
- RefusedAug 2026
Coverdale Road, N11
Part single, part two storey rear extension following removal of the conservatory roof. Conversion of the existing garage into habitable…
26/2394/HSE · Barnet CouncilHouseholder application
- ApprovedAug 2026
Oakleigh Road North, N20
Roof extension involving rear dormer window
26/2834/192 · Barnet CouncilLawful development certificate
- RefusedAug 2026
Oakleigh Road North, N20
Erection of a two storey rear outbuilding with mansard roof
26/2091/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
Friern Barnet's housing stock — and what works on each
Friern Barnet is quieter than its name-recognition neighbours — and that's exactly why the value is good. Four kinds of street, four different playbooks.
The 1930s semis around Friern Barnet Lane and the village green. Stand on the Lane and you're looking at the borough's favourite raw material: bay windows, hipped roofs, proper gardens. Up top, a hip-to-gable loft with rear dormer (£55,000–£90,000) trades the wasted hip for a genuine double bedroom with en-suite. At ground level, a single-storey rear (£45,000–£90,000) dissolves the wall between kitchen and garden. Both usually avoid a full application, which makes them low-friction extensions in N11.
The Edwardian terraces towards New Southgate. Plots tighten near the station edge, and the smart money goes on the side-return extension (£35,000–£65,000) — the alley beside the kitchen becomes the missing width of a proper kitchen-diner — with dormer loft conversions the other proven move.
Princess Park Manor and the apartment stock. The converted Victorian hospital in its parkland is the local landmark — but apartments aren't extension candidates: flats have no permitted development rights, and managed estates bring their own consent layers. If you're trading an apartment for a nearby semi with extension potential priced in, we'll happily tell you what a house could become before you offer on it.
Post-war and infill streets. Where the plots square off and garages appear, good pound-per-metre gains come from garage conversions (£18,000–£35,000) and simple, efficient rear additions.
Every street is different. That's the point.
We design to Friern 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 Friern Barnet in 2026
No postcode premium applies in Friern Barnet — you're buying construction at the honest North London baseline. The table gives genuine build figures: labour and materials to a good standard, with VAT, professional fees and the kitchen fit-out costed separately:
| Extension type | Typical Friern 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 |
Run the numbers at £2,800–£4,200 per square metre — the North London baseline — and a 21m² rear addition pencils out at roughly £59,000–£88,000 of build cost. When the quote comes, after a free site visit, it comes fixed and itemised: the total on page one is the total on the final invoice.
Permissions, handled
Planning permission in Friern Barnet — what you need to know
Start with the good news: a full application is often unnecessary in N11. Before any application is made, the permitted development rules give a semi or terrace 3m of single-storey rear extension and a detached house 4m; add prior approval under the larger home extension scheme and the limits move out to 6m and 8m. Lofts get a generous volume allowance of their own — the reason so many hip-to-gable schemes in N11 need no full application.
Full permission still applies to: two-storey and wrap-around schemes, front extensions, and all flats and maisonettes — including everything at Princess Park Manor, where estate consents add a further layer. Conservation status we never assume: your address goes against the council's conservation map during the free consultation, because a conservation designation strips back permitted development rights.
On timing, budget about eight weeks from validation for Barnet to decide a standard householder application. Party walls come with the territory in a neighbourhood of semis and terraces — allow £1,000–£2,500 per affected neighbour if surveyors are appointed, and open the conversation over the fence early; the formal notices are ours to prepare and serve. And whenever a project runs under permitted development, we secure a Lawful Development Certificate, putting the works beyond question when you sell. Where N11 crosses into Enfield or Haringey, the rules shift with the council; our guide to house extensions in North London takes the three boroughs in turn.
How it works
How it works
- Free site visit — we come to your N11 home, look at the roof, the garden and the side access, and give you a frank read on feasibility, cost and route.
- Design & drawings — a proper drawing package with 3D visuals, moulded to your house and the life inside it.
- Planning, handled — the Barnet Council paperwork is ours from first draft to final decision.
- Fixed-price build — our established North London team builds it through to building control sign-off and a tidy, complete handover.
Our work
Recent work near Friern Barnet
For a flavour of the build team's work, see the full house transformation in Hadley Wood that took a family home from 120m² to 360m² in the Hadley Wood write-up. Whichever direction you're leaning in Friern Barnet, ask at the site visit and we'll talk it through.
Questions, answered
Friern Barnet extension FAQs
Which schemes does Barnet Council approve on N11 semis?
Hip-to-gable loft conversions with rear dormers, and single-storey rear extensions, come up again and again in Barnet's decisions. Both are tailor-made for N11's 1930s semis.
How much is a hip-to-gable loft on a Friern Barnet semi?
£55,000–£90,000 for the build, typically 6–10 weeks on site, and usually achievable under permitted development thanks to the generous loft volume allowance. It converts the dead hip space into a full double bedroom with en-suite.
Will my N11 extension need a planning application?
Often not. Rear extensions up to 3m (4m detached) are permitted development, the prior approval route stretches that to 6m/8m, and most lofts fit the volume allowance. Two-storey schemes, wrap-arounds and front extensions need full permission — and we recommend a Lawful Development Certificate for anything built without one.
Can apartments at Princess Park Manor be extended?
Realistically, no — flats have no permitted development rights and the managed estate brings its own consent requirements. If you're weighing a move from an apartment to a nearby N11 house, we'll assess the house's extension potential before you commit.
What's the timeline from first call to finished extension?
Site visit within days; design and drawings 4–8 weeks; Barnet's decision around eight weeks (quicker for lawful development routes); then 2–4 months on site for a single-storey scheme or 6–10 weeks for a loft. Most families are in their new space within 6–9 months of picking up the phone.
Which areas around Friern Barnet do you cover?
All of them — North Finchley, Whetstone, New Southgate, Southgate, Muswell Hill, East Barnet and the Wood Green border.
What we build in Friern Barnet
The same team designs, gets planning and builds — one fixed, itemised price whichever route your Friern Barnet project takes.
- Kitchen extensions in Friern Barnet
- Side return extensions in Friern Barnet
- Double-storey & wrap-around in Friern Barnet
- Loft conversions in Friern Barnet
- Orangeries in Friern Barnet
- Garden rooms & offices in Friern Barnet
Checking the rules for Friern 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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