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, 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 — and note that the schemes approved in NW7 in the latest decision window, hip-to-gable lofts and single-storey rears, are exactly what this housing was made for. Book a free site visit and we'll give you the honest verdict for your particular street.
Live planning data
What Barnet Council is approving in Mill Hill right now
We keep a running log of every residential planning decision in North London, so what the council will accept is a matter of record here, not conjecture. In the most recent two-week decision window, Barnet Council approved 63 residential schemes borough-wide, six of them in NW7. These are real Mill Hill approvals from that window:
- 6 The Circle, NW7 — hip-to-gable roof extension with rear dormers and a Juliette balcony
- 74 Laleham Avenue, NW7 — single-storey rear extension
- 22 Worcester Crescent, NW7 — loft scheme, approved as a variation of previously approved plans
The list reads like a miniature of the borough: lofts and single-storey rears are the well-trodden paths in NW7, just as they are across Barnet. The Worcester Crescent decision carries its own small lesson — approved plans can be formally varied when a design evolves, which is far better than building something that doesn't match the consent. If your project looks like the ones above, you're on safe ground — and we design to that grain.
Source: planning decisions published by Barnet Council. They're cited to show the local approvals current — these aren't our commissions, and any given application succeeds or fails on its own specifics.
Local knowledge
Mill Hill's housing stock — three markets in one postcode
Few postcodes change character as quickly as NW7. 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 — is a conservation area, and the most sensitive corner of NW7. Permitted development rights are restricted here, 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 highest-value 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. The NW7 approvals above — hip-to-gable lofts, dormers, a single-storey rear — show exactly this kind of scheme passing locally.
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 estimateHonest 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 keep appearing in the approvals list. 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 Village conservation area — where permitted development rights are restricted — 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.
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 the North London tradespeople we've worked with for years, 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
The build team's recent North London work spans a full house transformation taking a family home from 120m² to 360m², a 55m² garden room with kitchen and bathroom, and an Edwardian conversion in neighbouring Finchley. Let us know what you're considering and we'll walk you through the most relevant of them at your 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.
What has Barnet actually approved in Mill Hill recently?
Six NW7 residential schemes in the latest two-week window — including a hip-to-gable roof extension with rear dormers and Juliette balcony at 6 The Circle, a single-storey rear extension at 74 Laleham Avenue, and a loft scheme at 22 Worcester Crescent approved as a variation of earlier plans.
I'm in Mill Hill Village — does the conservation area stop me extending?
No — it changes the approach. Permitted development rights are restricted around The Ridgeway, so schemes go through full applications with materials and rooflines under real scrutiny. 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?
The same pair the approvals data keeps endorsing: 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. 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.
Nearby areas we cover
What clients say
Rated 5.0 on Google
“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.…” read the full review
“Really impressed with the entire project. The side extension and conservatory have been finished to a very high standard and the team made the process straight forward and stress-free. It’s transformed the space and added so much value, would definitely recommend.”
“Brilliant experience with the extension company, transparent from the word go. Completed a double story extension for me and I couldn’t be more pleased. Thank you”
“I got the extension company to do a bathroom refurb for us a January they done a great job they managed to fit in a large shower as well as a bath”
Reviews shown word for word from our Google profile. Read all 8 reviews on Google
Free site visit
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Free site visit anywhere in Mill Hill, honest feasibility advice and a fixed, itemised price — design, planning and build handled end to end by the Pine Grove team.
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