Area guide · EN4
House Extensions in Cockfosters (EN4)
Planning a house extension in Cockfosters? We design, gain planning permission and build extensions and loft conversions across EN4, from the 1930s avenues to the larger detached houses towards Trent Park and Hadley Wood. A single-storey rear extension here typically costs £50,000–£100,000 to build, your application goes to Enfield or Barnet depending on which side of the borough boundary your house sits, and the hipped roofs on the avenues lend themselves to a hip-to-gable loft conversion. Book a free site visit and we'll tell you what your house can take.
Planning in Cockfosters
What Enfield Council has been approving in Cockfosters
The decisions below are Enfield's, from its Cockfosters ward. That ward is bigger than the village around the station: it runs north-west through Hadley Wood and south-east past Bramley Road into N14 towards Oakwood, so some cards carry an N14 address. The EN4 streets on the Barnet side of the boundary fall in Barnet's East Barnet ward, and their decisions are on our East Barnet page.
Two things help when reading the cards. Enfield's notices rarely say "hip to gable": they describe the same loft as an extension of the roof to the side to form a gable, usually with a rear dormer and front rooflights. And a prior approval card states the depth and height applied for, which makes it a handy yardstick if you are weighing a deeper single-storey rear under the larger home extension rules. Refusals are counted alongside the approvals, and they are just as useful when a scheme is being shaped.
Recent planning decisions around Cockfosters
Extension, loft and basement applications decided in Enfield's Cockfosters ward, 23 Sep 2025 to 22 Sep 2026.
The newest decisions in those wards
- ApprovedSep 2026
Gloucester Gardens, EN4
Extension of roof to side to form gable with flank window, rear dormer and front roof lights.
26/03308/CEA · Enfield CouncilLawful development certificate
- ApprovedSep 2026
De Bohun Avenue, N14
Demolition of existing kitchen and erection of single storey rear/side extension with part flat, part pitched roof and rooflights with…
26/02499/HOU · Enfield CouncilHouseholder application
- ApprovedSep 2026
Sovereign Mews, EN4
Single storey rear extension with roof lights.
26/02576/HOU · Enfield CouncilHouseholder application
- ApprovedSep 2026
Gloucester Gardens, EN4
Single storey rear extension 6m deep x 3.3m high (3m high to eaves).
26/03304/PRH · Enfield CouncilPrior approval, larger home extension
- ApprovedAug 2026
Addison Avenue, N14
Single storey side/rear wraparound extension involving demolition of existing rear conservatory, garage and front store.
26/02206/HOU · Enfield CouncilHouseholder application
- ApprovedAug 2026
Cowper Gardens, N14
Single storey rear extension 4m deep x 3m high (3m high to eaves).
26/02781/PRH · Enfield CouncilPrior approval, larger home extension
- ApprovedAug 2026
Kent Drive, EN4
Extension of roof to side to form gable with new flank window, rear dormer and front roof lights.
26/02587/CEA · Enfield CouncilLawful development certificate
- RefusedJul 2026
Westpole Avenue, EN4
Part single, part two-storey rear/side extension and front porch incorporating a rear dormer with front rooflights, Juliet balcony to the…
26/01996/HOU · Enfield CouncilHouseholder application
Look a reference up on the council’s own register: Enfield 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
Cockfosters' housing stock — and what works on each
Cockfosters grew up around the tube. The Piccadilly line terminus opened in 1933, and the wide avenues of hipped-roof semis and detached homes followed it — generous plots, side passages, deep gardens, with Trent Park on the doorstep. Here's how we'd extend each part of it.
The hipped-roof avenues (around Westpole Avenue, Kent Drive and Gloucester Gardens, and west towards Heddon Court Avenue). Classic tube-boom stock: bay-fronted, hipped-roof, and built for two moves. The hip-to-gable loft with rear dormer (£60,000–£100,000 here) adds a double bedroom and en-suite without touching the garden, and roof schemes of this kind recur through the ward's decisions; our Cockfosters loft conversion guide takes the loft options roof by roof. The single-storey rear extension (£50,000–£100,000) opens the kitchen across the full width of the plot; under the larger home rules a 6m depth is achievable with prior approval. Plenty of owners phase both a year or two apart.
Detached Cockfosters — towards Trent Park and the Hadley Wood border. The bigger detached homes carry the area's premium. Permitted development stretches further on detached houses — 4m rear as standard, up to 8m with prior approval — and the plots take double-storey rear extensions (£85,000–£180,000) and wrap-arounds (£80,000–£160,000) comfortably. Trent Park itself is both an Enfield conservation area and green belt, so for houses on its edge we check the constraints before anyone falls in love with a scheme. Further north, Hadley Wood has a conservation area of its own around the Crescents and Lancaster Avenue.
The two-borough streets. The boundary between Enfield and Barnet does not follow Cockfosters Road. West of the road, Enfield's side reaches a short way in, taking in Chalk Lane, and Barnet begins around Games Road and, just south-west of the station, Mount Pleasant. Further south the line cuts across Heddon Court Avenue and Cat Hill: both have had applications decided by each council in the past year, so neighbours on the same road can be dealing with different councils. The national permitted development rules are the same either side; validation checklists, local policies and case officers are not. We prepare applications for either council, so whichever side of the line you're on, the paperwork is handled.
Trent Park's conservation area. It is more than the park. The designation takes in houses along Cockfosters Road and Bramley Road, and Enfield's 2006 Article 4 direction covers some of the Cockfosters Road houses: on elevations facing or visible from a road or open space, changes to windows, roofs, porches, front walls and brickwork need planning permission there. On the Barnet side, the eastern tip of the Monken Hadley conservation area reaches Games Road.
Every street is different. That's the point.
We design to Cockfosters'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 Cockfosters in 2026
Cockfosters is a premium pocket — build costs typically run 10–15% above the North London baseline, reflecting larger houses and higher finish expectations. These are realistic all-in build ranges, excluding VAT, professional fees and kitchen fit-out:
| Extension type | North London baseline plus 10–15% (apply across EN4) | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £40,000 – £75,000 | 2–3 months | Often permitted development |
| Single-storey rear | £50,000 – £100,000 | 3–4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £60,000 – £125,000 | 3–4 months | Often permitted development |
| Hip-to-gable loft + rear dormer | £60,000 – £100,000 | 6–10 weeks | Usually permitted development |
| Wrap-around extension | £80,000 – £160,000 | 4–6 months | Full application |
| Double-storey rear | £85,000 – £180,000 | 5–7 months | Full application |
| Garage conversion | £20,000 – £40,000 | 4–6 weeks | Usually permitted development |
The North London baseline runs £2,800–£4,200 per square metre; in Cockfosters budget £3,100–£4,700/m². Once we've walked your property on the free site visit, your quote comes back fixed and broken down line by line — and the figure on the contract is the figure on the final invoice.
Permissions, handled
Planning permission in Cockfosters — what you need to know
Start with the council question. Most of Cockfosters, including Trent Park and the avenues south-east of the station, is Enfield's. The streets from Games Road and Mount Pleasant westwards are Barnet's, and on Heddon Court Avenue and Cat Hill it depends on the house. It changes where your forms go and whose local policies apply — we confirm it from your address on day one. For how the two councils compare with Haringey, see our borough-by-borough guide to North London.
Plenty of Cockfosters extensions don't need a full application. Under permitted development a semi can push a single-storey rear extension 3m out — detached homes get 4m — and the larger home prior-approval process stretches those depths to 6m and 8m respectively. Loft conversions have their own volume allowance, which is why hip-to-gable schemes on EN4 semis can go through as lawful development. None of that applies in the same way inside the Trent Park or Hadley Wood conservation areas, where the larger home route and roof enlargements fall away.
Where you do need permission: double-storey rears, wrap-arounds, flats and maisonettes, and homes where previous owners have already used up permitted development rights. Whichever side of the boundary you're on, plan for roughly eight weeks from validation to decision — both councils work to the same householder target.
Party walls: much of the avenue stock is semi-detached, so the Party Wall Act applies to a large share of projects here — budget £1,000–£2,500 per affected neighbour if surveyors are appointed, and start the conversation early. We serve the notices and manage the process.
Paperwork that pays: wherever a project proceeds under permitted development, we recommend a Lawful Development Certificate — it makes your extension bulletproof when you come to sell, and at Cockfosters prices that matters.
How it works
How it works
- Free site visit — we walk your property, talk through what you want, and give straight answers on feasibility, cost and which council you're dealing with.
- Design & drawings — we draw the scheme up properly: scaled plans and 3D visuals shaped around your EN4 house and the way your family actually uses it.
- Planning, handled — we prepare and submit to Enfield or Barnet, whichever side of the boundary you're on, and manage it to decision.
- Fixed-price build — Pine Grove Design & Build's own team takes it on site, through building control sign-off, and leaves the place tidy on handover day.
Our work
Recent work near Cockfosters
Just along EN4 in Hadley Wood, we took a family home through a full house transformation from 120m² to 360m² — you'll find it, with photos, in the Hadley Wood case study. When we come round, ask about it — we'll talk through whatever sits closest to your own brief.
Questions, answered
Cockfosters extension FAQs
Which council decides my extension in Cockfosters?
Enfield for most of it: its Cockfosters ward covers Trent Park, the avenues south-east of the station and Hadley Wood. Barnet decides the streets from Games Road and Mount Pleasant westwards, which sit in its East Barnet ward. The boundary is not Cockfosters Road itself, and it runs through Heddon Court Avenue and Cat Hill, where both councils have decided applications. We confirm your council from the address before any design work starts.
How much should I budget for an extension in EN4?
Around £50,000–£100,000 for a single-storey rear build, £60,000–£100,000 for a hip-to-gable loft, and £85,000 upwards for double-storey schemes — excluding VAT and fees. Cockfosters builds at roughly £3,100–£4,700/m², about 10–15% above the North London norm.
What suits Cockfosters' 1930s houses?
The hipped roofs make a hip-to-gable loft with rear dormer the natural first move, and on Enfield's side it will be described as an extension of the roof to the side to form a gable. At ground level, a single-storey rear extension opens the kitchen to the garden.
Can I build a 6m rear extension in Cockfosters?
On many semis, yes — via the larger home prior-approval route (up to 8m on detached homes), which involves notifying the neighbours rather than making a full application. The route is not available in a conservation area, so houses inside Trent Park's or Hadley Wood's need planning permission instead. We'll confirm your eligibility at the site visit.
Does living near Trent Park restrict what I can build?
Living near the park doesn't in itself remove your permitted development rights. The Trent Park conservation area does take in houses on Cockfosters Road and Bramley Road, though, and some of the Cockfosters Road houses are also under an Article 4 direction covering their street-facing elevations. The park is green belt as well. We check your address against both councils' conservation and constraint maps before designing — it takes minutes and avoids expensive surprises.
Do Barnet and Enfield handle applications differently?
The national permitted development rules and the eight-week householder target are the same at both. What differs is each council's validation checklist, local plan policies and design guidance, so the drawings and supporting documents are prepared for whichever council will decide.
What we build in Cockfosters
The same team designs, gets planning and builds — one fixed, itemised price whichever route your Cockfosters project takes.
- Kitchen extensions in Cockfosters
- Side return extensions in Cockfosters
- Double-storey & wrap-around in Cockfosters
- Loft conversions in Cockfosters
- Garage conversions in Cockfosters
- Annexes in Cockfosters
- Loft conversions in Cockfosters — local guide
Checking the rules for Cockfosters 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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