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Improving at NW4 3ST

What you could build at NW4 3ST: the planning rules at this address, what neighbours have built and how big, planning decisions nearby, rough costs and the value an extension adds, and how to get started. In West Hendon, Barnet.

99extensions seen within 600 m in the last 10 years

14loft conversions within 600 m in the last 10 years

77%of 82 householder applications nearby approved (since 2023)

45.3extensions per 1,000 homes in the neighbourhood (10 years)

● work seen on energy certificates · ● application approved · ● refused · ● pending or other · ● this postcode

The rules at this address

Mostly flats at this postcode. Flats have no permitted development rights, so almost any extension or loft conversion needs planning permission, and the freeholder's consent under the lease.
Not in a conservation area (from council registers).
Article 4 direction (Article 4 Small Houses in Multiple Occupation (HMO) Area 1): some rights normally allowed have been removed here. Check what it covers with the council before relying on permitted development.
Listed buildings need listed building consent for most changes, inside and out: check the National Heritage List.
To be certain work is permitted development, apply for a lawful development certificate (about £129 for householders in England). Building regulations apply either way.

What neighbours have built

Home	Work	Seen	Space added	Floor area	Rooms	Distance
24, High Mount	Extension	2026	+27 m²	59 m² → 86 m²	–	72 m
43, Dartmouth Road	Extension	2026	+25 m²	108 m² → 133 m²	–	217 m
32, Algernon Road	Extension	2026	+10 m²	63 m² → 73 m²	3 → 3	234 m
Flat 3, 70, Vivian Avenue	Extension	2026	+27 m²	31 m² → 58 m²	3 → 3	287 m
4, Brent View Road	Extension	2026	+24 m²	78 m² → 102 m²	–	475 m
5, Elliot Road	Extension	2026	+87 m²	128 m² → 215 m²	–	493 m

Planning applications nearby

Address	Work	Outcome	Decided	Drawings and agent
14, Neeld Crescent, Nw4 3rr	Side return or wrap-around	Under consideration	–	26/3641/HSE
45, Foscote Road, Nw4 3se	Two-storey extension	Under consideration	–	26/3658/HSE
1, Vaughan Avenue, Nw4 4ht	Loft or dormer	Under consideration	–	26/3564/HSE
10, Vaughan Avenue, Nw4 4hu	Loft or dormer	Under consideration	–	26/3538/HSE
20, Dartmouth Road, Nw4 3hu	Loft or dormer	Under consideration	–	26/3435/HSE
33, Rundell Crescent, Nw4 3bs	Loft or dormer	Under consideration	–	26/3361/HSE

How often householder applications are approved

Work	West Hendon	Barnet	London	Typical decision time
All householder applications	87% (119)	76% (5649)	80%	8 weeks
Loft or dormer	75% (16)	81% (1882)	81%	8 weeks
Rear extension	74% (31)	66% (1643)	79%	8 weeks
Two-storey extension	90% (10)	74% (662)	72%	8 weeks
Other householder work	–	65% (389)	70%	8 weeks
Side return or wrap-around	71% (7)	85% (148)	88%	8 weeks
Windows, doors or cladding	100% (47)	95% (317)	90%	8 weeks
Outbuilding or garden room	–	81% (108)	79%	8 weeks
Side extension	–	94% (120)	86%	8 weeks
Garage conversion or garage

Cost and the value it adds

Across England and Wales, homes extended by a typical 30 m² and then resold rose about 11.1% more than similar homes nearby over the same years (124,884 resales). How extensions pay off by size, type and region.

Single-storey rear or side extension: about £2,000–£3,000 per m² (London £2,500–£4,000), plus fees and VAT
Loft conversion: about £45,000–£75,000 for a dormer; more for a mansard or hip-to-gable
Two-storey extension: about £1,800–£2,800 per m² of new floor
Garage conversion: about £15,000–£30,000
Basement: about £3,500–£5,000 per m², London mostly

Build costs are rough 2026 ranges from industry guides, not quotes. Get three quotes for your plans.

Move or improve?

The money you don't get back either way, for the same extra space in West Hendon.

Your home is worthExtra space you need (m²)Homes here sell for, per m²Building cost per m²Share of that an extension adds (%)

Move to a home 20 m² bigger (about £505,000)

Stamp duty on the new home	£15,250
Estate agent on yours 1.2% + VAT	£5,760
Solicitors, buying and selling	£3,000
Survey	£600
Removals	£1,500
Money gone	£26,110

Extend by 20 m²

Building, plus 15% for design, planning and contingency	£57,500
Less what it adds to your home's value 60% of the local price	−£63,000
Money gone	−£5,500

On these figures, extending loses about £31,610 less. Moving also changes the area, the schools and the commute; extending means months of building work and depends on planning.

Building costs vary a lot (a single-storey rear extension is often £2,000–£3,000 per m², more in London). How much space adds depends on the home and street: what extensions added to resale prices. A guide, not advice; nothing you type leaves this page.

Getting started

Look at what neighbours did. Open applications above to see drawings that were approved on similar houses, and who designed them.
Check the route: permitted development (with a lawful development certificate), prior approval for larger rear extensions, or full householder planning permission.
Get a measured survey and a designer: an architect, an architectural technologist or a designer who handles planning drawings.
Apply (householder permission is about £258 in England; councils aim to decide within 8 weeks).
Building regulations through the council's building control or an approved inspector, and party wall notices to neighbours if you build on or near the boundary.
Choose a builder: written quotes, a contract, staged payments, and check their insurance and references.

Find help: RIBA Find an Architect ↗ · CIAT architectural technologists ↗ · TrustMark tradespeople ↗ · Federation of Master Builders ↗ · Planning Portal guides ↗

General guidance, not planning or legal advice. Fees and rules as checked in October 2026; confirm with the council.

Energy certificates: MHCLG (OGL). Planning applications: GLA Planning London Datahub. Conservation areas and Article 4: planning.data.gov.uk (OGL).

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Improving at NW4 3ST

The rules at this address

What neighbours have built

Planning applications nearby

How often householder applications are approved

Cost and the value it adds

Move or improve?

Getting started

Go deeper

Improving at NW4 3ST

NW4 3ST is on High Mount

The rules at this address

What neighbours have built

Planning applications nearby

How often householder applications are approved

Cost and the value it adds

Move or improve?

Getting started

Go deeper

NW4 3ST is on High Mount