What you could build at W9 3NG: 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 Maida Hill, Westminster.
130extensions seen within 600 m in the last 10 years
10loft conversions within 600 m in the last 10 years
96.9extensions 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 Basement Development Permitted Rights Removed): 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 (126,300 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 Maida Hill.
Move to a home 20 m² bigger (about £720,000)
Stamp duty on the new home
£26,000
Estate agent on yours 1.2% + VAT
£7,848
Solicitors, buying and selling
£3,000
Survey
£600
Removals
£1,500
Money gone
£38,948
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
−£105,000
Money gone
−£47,500
On these figures, extending loses about £86,448 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.
13 Lancaster Road, London, W11 1ql
Rear extension
Approved
Nov 2025
PP/25/05876
59 Tavistock Road, London, W11 1ar
Windows, doors or cladding
Approved
Apr 2026
PP/25/05920
3, Second Avenue, W10 4rn
Other householder work
Approved
Nov 2025
25/05955/FULL
22, First Avenue, W10 4nl
Windows, doors or cladding
Approved
Oct 2025
25/06142/FULL
31, 31 Second Floor Flat C, Fermoy Road, W9 3nh
Loft or dormer
Approved
Oct 2025
25/05826/FULL
31, 31 Ground Floor Flat A, Fermoy Road, W9 3nh
Rear extension
Approved
Oct 2025
25/05827/FULL
39, 39 Second Floor Flat C, Fermoy Road, W9 3nh
Loft or dormer
Approved
Oct 2025
25/05828/FULL
39, 39 Ground Floor Flat A, Fermoy Road, W9 3nh
Rear extension
Approved
Oct 2025
25/05829/FULL
7, Octavia Mews, W9 3lq
Other householder work
Approved
Oct 2025
25/05774/FULL
12, 12 St Luke'S Road, London, W11 1dp
Rear extension
Approved
Oct 2025
PP/25/04807
4, 4 Malvern Close, London, W10 5yy
Rear extension
Approved
Sept 2025
CL/25/04271
4e, Shirland Mews, W9 3dy
Other householder work
Approved
Jul 2025
25/03670/P3JPA
59 Tavistock Road, London, W11 1ar
Windows, doors or cladding
Approved
Jul 2025
PP/25/02917
63, 65, Goldney Road, W9 2ar
Basement
Approved
Jul 2025
25/03274/P3JPA
7 Golborne Mews, London, W10 5sb
Windows, doors or cladding
Approved
Jun 2025
PP/25/02479
237 Kensal Road, London, W10 5db
Windows, doors or cladding
Approved
May 2025
CL/25/01981
63, 65, Goldney Road, W9 2ar
Basement
Refused
Apr 2025
25/01382/P3JPA
243 Kensal Road, London, W10 5db
Other householder work
Approved
Apr 2025
CL/25/01152
526, Basement Part And Ground Floor Front, Harrow Road, W9 3qf
Basement
Refused
Mar 2025
25/00298/P3JPA
243 Kensal Road, London, W10 5db
Rear extension
Refused
Feb 2025
PP/24/08144
63, 65, Goldney Road, W9 2ar
Basement
Withdrawn
Dec 2024
24/07654/P3JPA
39 Munro Mews, London, W10 5rz
Windows, doors or cladding
Approved
Nov 2024
PP/24/05940
40 Orchard Close, London, W10 5rb
Loft or dormer
Approved
Oct 2024
CL/24/05246
243 Kensal Road, London, W10 5db
Other householder work
Approved
Sept 2024
PP/24/04304
97 Edenham Way, London, W10 5xa
Rear extension
Approved
Aug 2024
PP/24/03099
39 Munro Mews, London, W10 5rz
Windows, doors or cladding
Refused
Jun 2024
PP/24/02269
381, Harrow Road, W9 3na
Other householder work
Under consideration
–
23/04055/APA
243 Kensal Road, London, W10 5db
Rear extension
Refused
Aug 2023
PP/23/03863
Outside 31 And 32 Orchard Close, Opposite 2 And 6 St Joseph'S Close On Bevington Road, London, W10 5ra
Other householder work
Approved
May 2023
CL/23/02309
6, Ground Floor, Fernhead Road, W9 3et
Other householder work
Refused
May 2023
23/03267/P3JPA
3, 7, Avenues Youth Project, Third Avenue, W10 4rs
Other householder work
Approved
Apr 2023
23/01934/APA
12 Mcgregor Road, London, W11 1de
Side return or wrap-around
Approved
May 2023
PP/23/01768
12 Mcgregor Road, London, W11 1de
Windows, doors or cladding
Approved
May 2023
PP/23/01778
12 Mcgregor Road, London, W11 1de
Windows, doors or cladding
Approved
Mar 2023
PP/23/00797
6 Lancaster Road, London, W11 1qp
Loft or dormer
Approved
Mar 2023
PP/23/00424
243 Kensal Road, London, W10 5db
Rear extension
Approved
Apr 2023
PP/23/00307
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.
–
88%
8 weeks
Basement
–
67% (12)
83%
7 weeks
Porch or front extension
–
–
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.