Where in Barnet does a house extension actually get determined?
Barnet postcode by postcode: what the housing is, and which council validates an extension application there. The fee column reproduces government's statutory England rates for 2026 and has nothing to do with what we charge to draw.
| Postcode | Area | Dominant stock | What it means for a house extension |
|---|
| NW7 | Mill Hill | Georgian villas, 1930s detached and semi-detached | NW7 is Mill Hill and nothing else; Barnet Council handles the extension, and case officers read it against the NW7 conservation-area map. |
| NW9 | Colindale / Kingsbury | Post-war flats, new-build | NW9 spans Colindale and Kingsbury, and either Barnet Council or Brent Council may determine an extension there. Both policies maps get checked first. |
| NW11 | Golders Green / Hampstead Garden Suburb | Arts & Crafts houses, Edwardian villas | Golders Green and Hampstead Garden Suburb both sit inside NW11, entirely within the borough, so Barnet Council validates every extension application from an NW11 address. |
| EN4 | East Barnet / Cockfosters | 1930s semi-detached dominates; Edwardian villas in Muswell Hill | EN4 takes in East Barnet and Cockfosters, shared between Barnet Council and Enfield Council. Confirm which authority validates before EN4 drawings are issued. |
| EN5 | Barnet / Arkley | Georgian fragments, 1930s semi-detached | Barnet town and Arkley sit wholly inside EN5, so the council validates every extension application coming from an EN5 address. |
| HA8 | Edgware / Burnt Oak | 1930s semi-detached, post-war flats | HA8 covers Edgware and Burnt Oak. Barnet Council determines applications there, under the Local Plan policies it has adopted for that corner of the borough. |
| N10 | Muswell Hill | Edwardian villas, 1930s semi-detached | N10 is Muswell Hill, where the boundary crosses the district: either Haringey Council or Barnet Council may determine an extension, decided street by street on the N10 map. |
| NW2 | Cricklewood / Neasden | Edwardian villas and terraces | NW2 covers Cricklewood and Neasden and is shared three ways, between Brent Council, Barnet Council and Camden Council. The address is checked against all three policies maps at the outset. |
Which Barnet neighbourhoods suit a house extension best?
In Barnet it is usually plot depth that decides an extension, with roof pitch and wall construction changing street to street on top of that. All three get measured before a design begins.
- Mill Hill (NW7) — house extension work in Mill Hill means georgian villas, 1930s detached and semi-detached. Mill Hill is Georgian and 1930s detached. Georgian rear elevations here are usually the listed or locally listed face of the building throughout NW7. Barnet Council decides the Mill Hill application, and Mill Hill Village anchors the Mill Hill location plan.
- Edgware (HA8) — house extension work in Edgware means 1930s semi-detached, post-war flats. Edgware is 1930s semi-detached, post-war flats. 1930s semis here have the deepest rear gardens in the area throughout HA8. Barnet Council decides the Edgware application, and Edgware Tube anchors the Edgware location plan.
- Colindale (NW9) — post-war flats, new-build defines Colindale, where post-war flats, new-build set what a house extension can do. Post-war houses on these estates often sit under an estate management scheme across NW9. Any Colindale house extension is validated by Barnet Council, with Colindale station the usual Colindale reference point on the site plan.
- Whetstone (N20) — a house extension in Whetstone starts from 1930s semi-detached, edwardian villas, and Whetstone reads as 1930s semi-detached, Edwardian villas. Edwardian plots here are wider in N20. Barnet Council assesses Whetstone house extensions against its own Whetstone character guidance, and the location plan we draw for Whetstone references Totteridge & Whetstone.
- East Finchley (N2) — Edwardian terraces, 1930s semi-detached defines East Finchley, where edwardian terraces, 1930s semi-detached set what a house extension can do. Edwardian plots here are wider across N2. Any East Finchley house extension is validated by Barnet Council, with Phoenix Cinema the usual East Finchley reference point on the site plan.
- Barnet (EN5) — a house extension in Barnet starts from georgian fragments, 1930s semi-detached, and Barnet reads as Georgian and Victorian high street, 1930s residential. Georgian rear elevations here are usually the listed or locally listed face of the building in EN5. Barnet Council assesses Barnet house extensions against its own Barnet character guidance, and the location plan we draw for Barnet references Barnet High Street.
- Finchley (N3, N12) — 1930s semi-detached, Edwardian villas defines Finchley, where 1930s semi-detached, edwardian villas set what a house extension can do. Edwardian plots here are wider across N3. Any Finchley house extension is validated by Barnet Council, with Finchley Central the usual Finchley reference point on the site plan.
How do conservation areas and Article 4 affect a house extension in Barnet?
Conservation areas covering Barnet: Barnet Council runs 20, and Mill Hill, Hendon, Golders Green are the ones Barnet owners meet most. A house extension inside a Barnet conservation area loses permitted development, so the Barnet submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Hampstead Garden Suburb a house extension is judged on the street elevation first.
Article 4 and your Barnet house extension: Barnet Council has made no borough-wide direction, so permitted development for a house extension in Barnet generally survives outside Barnet conservation areas and listed curtilages. A Lawful Development Certificate at £274 is how a N2 owner records that a house extension was lawful.
The building fabric around Barnet: 1930s semi-detached dominates; Edwardian villas in Muswell Hill, Finchley; Garden Suburb Arts & Crafts in Hampstead Garden Suburb; post-war flats in Colindale. Suburban outer-London borough; permitted development used heavily; Hampstead Garden Suburb has its own residents' trust with additional design controls. A house extension in Barnet is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to Barnet Council.
Which neighbouring authorities border Barnet?
- Camden — the Camden boundary runs against Barnet, so a house extension a street from Barnet is decided by Camden Council instead. Camden runs 40 conservation areas across NW1 and its neighbours, which is why house extensions priced for Barnet are re-checked against Camden policy whenever the Barnet address sits on that edge.
- Haringey — adjoining Barnet, with 29 conservation areas centred on N4. A house extension on the far side of the Barnet line is determined by Haringey Council, so the Barnet quote for house extensions is checked against Haringey guidance before it is issued.
- Enfield — the Enfield boundary runs against Barnet, so a house extension a street from Barnet is decided by Enfield Council instead. Enfield runs 22 conservation areas across EN1 and its neighbours, which is why house extensions priced for Barnet are re-checked against Enfield policy whenever the Barnet address sits on that edge.
- Harrow — adjoining Barnet, with 29 conservation areas centred on HA1. A house extension on the far side of the Barnet line is determined by Harrow Council, so the Barnet quote for house extensions is checked against Harrow guidance before it is issued.
Sources for this Barnet house extension page: borough policies maps and
conservation-area registers (2025–26), Royal Mail postcode district boundaries,
the Town and Country Planning (Fees for Applications) (England) Regulations, the Town
and Country Planning (General Permitted Development) (England) Order 2015 as amended,
and the Party Wall etc. Act 1996.
