Area guide · NW7
House Extensions in Mill Hill (NW7)
Planning a house extension in Mill Hill? We design, gain planning permission and build extensions and loft conversions across NW7 — the Village on The Ridgeway, the Broadway streets and Mill Hill East. Plan on £45,000–£100,000 to build a single-storey rear, with Barnet Council handling the applications. The one thing to settle before anything is drawn is whether your house sits inside the Mill Hill conservation area, and if so, whether one of its Article 4 directions covers it too. Book a free site visit and we'll give you the honest verdict for your particular street.
Planning in Mill Hill
What Barnet Council has approved in Mill Hill
Barnet publishes every decision it makes, so what the council will accept in NW7 is a matter of record rather than conjecture. The list further down this section is Barnet's Mill Hill ward: its newest householder applications, lawful development certificates and larger-home prior approvals, refusals included, each with its reference so you can pull the drawings and the officer's report.
Read it with the hill in mind. Down around the Broadway and Mill Hill East, where the interwar semis are, roof and rear work can often go through as a certificate or a prior approval. Up on The Ridgeway, inside the conservation area, the same scheme usually has to be a householder application, because the permitted development shortcuts are narrower there. A refused certificate is worth reading closely: it means the council found the scheme fell outside permitted development, not that a planning application for it would fail.
NW7 is also bigger than the ward. The postcode spreads across several Barnet wards, and its Edgwarebury side, for one, shows up in the decisions on our Edgware page instead.
Recent planning decisions around Mill Hill
Extension, loft and basement applications decided in Barnet's Mill Hill ward, 23 Sep 2025 to 22 Sep 2026.
The newest decisions in those wards
- ApprovedSep 2026
Longfield Avenue, NW7
Single storey rear extension with a proposed depth of 6.00 metres, maximum height of 2.81 metres and eaves height of 2.81 metres…
26/3099/PNH · Barnet CouncilPrior approval, larger home extension
- ApprovedSep 2026
Parkside, NW7
Part single, part two storey rear and side extension with new patio area with screening and access steps. Single storey front extension…
26/2616/HSE · Barnet CouncilHouseholder application
- ApprovedSep 2026
Brookfield Crescent, NW7
Part single part two storey side extension. Single storey front and rear extension following demolition of outbuilding. New front…
26/1593/HSE · Barnet CouncilHouseholder application
- ApprovedAug 2026
Highwood Hill, NW7
Retention and refurbishment of the existing dwellinghouse, including demolition and replacement of two storey side extensions, replacement…
26/1226/HSE · Barnet CouncilHouseholder application
- ApprovedAug 2026
Page Street, NW7
Single storey rear extension with new raised terrace area with railings and access steps and new gate. Partial hip to gable roof…
26/2414/HSE · Barnet CouncilHouseholder application
- ApprovedAug 2026
Hatherleigh Close, NW7
Roof extension involving rear dormer window and 3no. front facing rooflights
26/2826/192 · Barnet CouncilLawful development certificate
- RefusedAug 2026
Bittacy Rise, NW7
Conversion and extension of the existing garage to rear into habitable room including insertion of windows and doors
26/2181/192 · Barnet CouncilLawful development certificate
- ApprovedAug 2026
Brookfield Crescent, NW7
Two storey side extension following the demolition of existing garage
26/2266/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
Mill Hill's housing stock — three markets in one postcode
NW7 changes character quickly. Within a mile you can go from weatherboarded cottages and open fields to interwar semis to brand-new apartment blocks — and the right extension is different in each.
Mill Hill Village and The Ridgeway. The old village along The Ridgeway — weatherboarded cottages, historic institutions, green-belt fields rolling away behind — sits inside the conservation area and is the most sensitive corner of NW7. Materials and rooflines are scrutinised, and the green-belt edge brings volume limits of its own. Extensions absolutely still happen in the Village; they need conservation-literate design, honest materials and patience with detail. We treat that as the brief, not the obstacle.
The Broadway's 1930s suburbia. Around Mill Hill Broadway station the stock is classic interwar: hipped-roof, bay-fronted semis with side passages and good gardens. The two big moves are the hip-to-gable loft with rear dormer (£55,000–£100,000), turning the wasted hip into a double bedroom and en-suite, and the single-storey rear extension (£45,000–£100,000) — 3m under standard permitted development, up to 6m with larger-home prior approval. Hip-to-gables, dormers and deep single-storey rears are the everyday business of the ward's decision list.
Mill Hill East's newer builds. The newer homes around Mill Hill East are a different animal: on modern developments, permitted development rights are sometimes removed by planning condition, so the routes that work on a 1930s semi can't be assumed. We check the original consent before designing — if PD is intact, the standard options apply; if not, a well-judged full application does the job.
Every street is different. That's the point.
We design to Mill Hill'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 estimateThe Mill Hill conservation area and its Article 4 directions
Barnet designated the Mill Hill conservation area in 1968. It follows The Ridgeway along the top of the hill, and Hammers Lane and Holcombe Hill are among the roads inside its boundary.
Being in the conservation area already changes the national rules. Roof extensions such as dormers and hip-to-gables are not permitted development there at all, and nor are side extensions, rear extensions of more than one storey or the larger-home prior approval route. A modest single-storey rear can still be permitted development, unless an Article 4 direction says otherwise.
On parts of the conservation area, one does. Two directions apply here: one made in 1970 and an Article 4(2) direction made in 2007. Neither covers the whole area; both take away the right to extend the house (Part 1, Class A), together with other roof alterations, porches, outbuildings, hard surfaces, and boundary walls, fences and gates. On those roads, even the modest rear extension needs a planning application. The council's own maps show exactly which houses the directions cover, and it is the first thing we check on a Ridgeway address, along with the green belt that wraps the ridge. Our conservation area guide explains what changes once you are inside a boundary.
Honest numbers
What a house extension costs in Mill Hill in 2026
Build budgets in Mill Hill realistically land in the bands below — labour and materials to a proper standard, with VAT, professional fees and kitchen fit-out sitting outside the figures:
| Extension type | Typical Mill Hill cost | On-site time | Usual planning route |
|---|---|---|---|
| Side-return extension | £35,000 – £70,000 | 2–3 months | Often permitted development |
| Single-storey rear | £45,000 – £100,000 | 3–4 months | Often permitted development |
| Kitchen extension (incl. mid-range kitchen) | £55,000 – £120,000 | 3–4 months | Often permitted development |
| Hip-to-gable loft + rear dormer | £55,000 – £100,000 | 6–10 weeks | Usually permitted development |
| Wrap-around extension | £70,000 – £155,000 | 4–6 months | Full application |
| Double-storey rear | £75,000 – £175,000 | 5–7 months | Full application |
| Garage conversion | £18,000 – £38,000 | 4–6 weeks | Usually permitted development |
Mill Hill spans the North London baseline of £2,800–£4,200 per square metre, with Village-side and conservation-grade work typically running up to 10% above it — careful detailing and better materials cost more, and on those streets they're worth it. Every Mill Hill quote we issue follows a free site visit and arrives fixed and itemised — the total you agree to at the start is the total you settle at the end.
Permissions, handled
Planning permission in Mill Hill — what you need to know
On most NW7 streets, you may not need a full application. Permitted development hands semis and terraces a 3m single-storey rear allowance and detached houses 4m; secure prior approval via the larger home extension scheme and you can go to 6m, or 8m on a detached home. Loft conversions enjoy a generous volume allowance, which is why hip-to-gable schemes feature so heavily among the ward's certificates. A standard householder application typically takes Barnet somewhere near eight weeks to decide.
Where permission is definitely needed: double-storey and wrap-around schemes, flats and maisonettes, the Mill Hill conservation area — where the rules above apply — and homes where PD has been used up or removed by condition, which is worth checking in Mill Hill East. The green-belt edges around the Village bring their own volume limits; we check the constraints before you fall in love with a scheme that can't pass.
Party walls: budget £1,000–£2,500 per affected neighbour if surveyors are appointed, and start the friendly conversation early. We serve the notices as part of the job.
Our approach: we design to what Barnet Council demonstrably approves, and if lawful development is the wiser path we'll secure the certificate ourselves — giving you watertight paperwork for any future remortgage or sale. For how Barnet sits alongside Enfield and Haringey, and where each council's boundary runs, see our borough-by-borough guide to North London extensions.
How it works
How it works
- Free site visit — whether you're in the Village or off the Broadway, we walk the house with you and give a candid view on feasibility, budget and the right consent path.
- Design & drawings — a thorough drawing set and 3D visuals that respond to your house's architecture and your household's habits.
- Planning, handled — from first form to final decision, the Barnet Council application is prepared, lodged and managed by us.
- Fixed-price build — built by our own North London build team, certified by building control, handed back spotless.
Mill Hill at the Ridgeway scale
The Ridgeway and the Uphill roads play in a different league from the rest of NW7: substantial detached houses where the natural project is a double-storey rework, a basement, or extension plus remodel in a single programme. That work leans on Barnet's design expectations, and on some plots meets the green belt too.
It is precisely what our large and luxury extensions service covers, with the numbers banded plainly in the luxury extension cost guide and the green belt rules covered in our guide.
Our work
Recent work near Mill Hill
For the Ridgeway-scale briefs above, see the build team's recent full house transformation in Hadley Wood, which took a family home from 120m² to 360m², in the Hadley Wood write-up. Closer still, Pine Grove's own team built a new block of flats with a penthouse here in Mill Hill, from demolition to completion. Let us know what you're considering for your Mill Hill house and we'll go through it at the site visit.
Questions, answered
Mill Hill extension FAQs
What do extensions cost in NW7?
Typically £45,000–£100,000 for a single-storey rear, £55,000–£100,000 for a hip-to-gable loft and £18,000–£38,000 for a garage conversion — excluding VAT and fees. Mill Hill spans the North London baseline of £2,800–£4,200 per square metre, with Village conservation work up to around 10% above. Fixed, itemised quotes after a free visit.
Where can I see what Barnet has decided in Mill Hill?
On this page: the newest decisions in Barnet's Mill Hill ward, each with its month, street, outcome and reference, alongside the ward's totals for the past twelve months. Put any reference into Barnet's planning register to see the drawings and the officer's reasoning.
I'm in Mill Hill Village — does the conservation area stop me extending?
No — it changes the approach. Dormers, hip-to-gables and side extensions need planning permission anywhere in the conservation area, and on the roads covered by its Article 4 directions even a single-storey rear does. Sympathetic, conservation-literate design gets approved; off-the-shelf design doesn't.
Does the green belt affect what I can build?
It can on the Village edges, where openness rules limit volume. Most NW7 gardens are unaffected, but if your plot backs onto the fields we check the constraints before any design work — it's one of the first things we confirm at the site visit.
What's the smartest project for a 1930s semi near the Broadway?
A hip-to-gable loft with rear dormer for two extra rooms upstairs, and a single-storey rear — 3m under permitted development, up to 6m via prior approval — for an open-plan kitchen-diner. Outside the conservation area both can usually avoid a full application, and together they roughly double the useful living space.
My Mill Hill East house is a newer build — am I free to extend?
Possibly, but check first: developers' planning consents sometimes remove permitted development rights by condition. We pull the original consent for your estate before designing, then route the project through PD or a full application accordingly.
What we build in Mill Hill
The same team designs, gets planning and builds — one fixed, itemised price whichever route your Mill Hill project takes.
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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