What you could build at NW4 2SX: 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 Hendon Central, Barnet.
101extensions seen within 600 m in the last 10 years
10loft conversions within 600 m in the last 10 years
73.1extensions 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
Houses usually have permitted development rights: some rear extensions (typically up to 3 m deep for a semi or terrace, 4 m detached), loft conversions within volume limits, and porches can go ahead without planning permission. Larger single-storey rear extensions (up to 6 m / 8 m) can use the “prior approval” neighbour scheme.
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.
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 Hendon Central.
Move to a home 20 m² bigger (about £604,000)
Stamp duty on the new home
£20,200
Estate agent on yours 1.2% + VAT
£7,200
Solicitors, buying and selling
£3,000
Survey
£600
Removals
£1,500
Money gone
£32,500
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
−£62,400
Money gone
−£4,900
On these figures, extending loses about £37,400 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.
From energy certificates: an extension where a later certificate shows more floor space, a loft conversion where roof rooms appear. Certificates come with sales, lettings and some building work, so the year is when it was first seen.
Not every extension shows here. We only see building work when a new energy certificate is lodged, which happens when a home is sold, let or newly built. A loft or extension added since then won't appear, even with planning permission and building control sign-off, because those records aren't published as open data outside London. Missing work doesn't mean missing paperwork.
26/2605/HSE
50, Neeld Crescent, Nw4 3rr
Rear extension
Refused
Jul 2026
26/2434/PNH
27, Fuller Street, Nw4 4rr
Rear extension
Approved
Jul 2026
26/2069/HSE
14, Somerset Road, Nw4 4ep
Loft or dormer
Approved
Jul 2026
26/1852/HSE
25, Wykeham Road, Nw4 2tb
Rear extension
Approved
May 2026
26/1262/HSE
27, Fuller Street, Nw4 4rr
Rear extension
Refused
May 2026
26/1027/HSE
31, Egerton Gardens, Nw4 4bb
Loft or dormer
Withdrawn
May 2026
26/0921/HSE
29, Egerton Gardens, Nw4 4bb
Loft or dormer
Withdrawn
Apr 2026
26/0751/HSE
20, Heriot Road, Nw4 2dg
Other householder work
Approved
Apr 2026
26/0781/HSE
33, Cheyne Walk, Nw4 3qh
Loft or dormer
Approved
Mar 2026
26/0489/HSE
72, Wykeham Road, Nw4 2st
Two-storey extension
Approved
Mar 2026
26/0346/HSE
20, Heriot Road, Nw4 2dg
Side return or wrap-around
Approved
Mar 2026
26/0128/HSE
48, Crespigny Road, Nw4 3dx
Loft or dormer
Approved
Jan 2026
25/4862/HSE
70, Brent Street, Nw4 2es
Rear extension
Not needed / lawful
Jan 2026
25/4801/PNH
4a, Carla House, Rundell Crescent, Nw4 3bp
Outbuilding or garden room
Approved
Apr 2026
25/4693/HSE
16, Sydney Grove, Nw4 2eh
Two-storey extension
Approved
Jan 2026
25/4514/HSE
20, Heriot Road, Nw4 2dg
Side return or wrap-around
Refused
Mar 2026
25/4388/HSE
70, Brent Street, Nw4 2es
Rear extension
Not needed / lawful
Nov 2025
25/3984/PNH
70, Brent Street, Nw4 2es
Rear extension
Not needed / lawful
Nov 2025
25/3985/PNH
84, Bell Lane, Nw4 2ae
Rear extension
Approved
Oct 2025
25/3633/PNH
77, The Burroughs, Nw4 4ax
Rear extension
Approved
Oct 2025
25/3387/HSE
17, Prothero Gardens, Nw4 3sj
Rear extension
Approved
Sept 2025
25/3359/HSE
20, Heriot Road, Nw4 2dg
Loft or dormer
Approved
Sept 2025
25/3267/HSE
19, Rundell Crescent, Nw4 3bs
Rear extension
Approved
Sept 2025
25/3168/HSE
20, Heriot Road, Nw4 2dg
Rear extension
Refused
Sept 2025
25/3150/PNH
9, The Crest, Nw4 2hn
Rear extension
Approved
Aug 2025
25/2552/HSE
17, Babington Road, Nw4 4ld
Loft or dormer
Approved
Aug 2025
25/2456/HSE
20, Prothero Gardens, Nw4 3sl
Loft or dormer
Refused
Jul 2025
25/2458/HSE
22, Sydney Grove, Nw4 2eh
Rear extension
Approved
Jul 2025
25/2141/HSE
9, The Crest, Nw4 2hn
Rear extension
Not needed / lawful
Jun 2025
25/1934/PNH
22, Sydney Grove, Nw4 2eh
Rear extension
Refused
Jun 2025
25/1709/PNH
20, Glebe Crescent, Nw4 1bu
Loft or dormer
Withdrawn
Jun 2025
25/1421/HSE
12, Prothero Gardens, Nw4 3sl
Porch or front extension
Approved
Mar 2025
25/0559/HSE
9, Prothero Gardens, Nw4 3sj
Loft or dormer
Refused
Apr 2025
25/0520/HSE
41, Egerton Gardens, Nw4 4bb
Two-storey extension
Approved
Feb 2025
24/5612/HSE
Householder applications validated since 2023 within 600 m. The council's page has the drawings, the decision notice and who the agent or architect was. Hover a row for the description. Source: GLA Planning London Datahub.
–
94% (157)
88%
8 weeks
Basement
–
82% (92)
83%
8 weeks
Porch or front extension
–
86% (131)
81%
8 weeks
Share of decided applications approved since 2023 (number decided in brackets). Withdrawn applications aren't counted; many are withdrawn when refusal looks likely.