What you could build at W1H 2PY: 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 Bryanston & Dorset Square, Westminster.
167extensions seen within 600 m in the last 10 years
7loft conversions within 600 m in the last 10 years
47.3extensions 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.
In the Portman Estate conservation area: permitted development is narrower (for example no side extensions or roof cladding), and demolition and works to trees need consent.
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.
93, 95, 93-95 Basement East And Ground Floor East, Bell Street, Nw1 6tl
Basement
Under consideration
–
26/06849/P3JPA
99, Seymour Place, W1h 5tg
Other householder work
Under consideration
–
25/09289/FULL
15, Rodmarton Street, W1u 8bl
Rear extension
Approved
May 2026
26/00539/FULL
15, 16, 15-16, Montagu Mews South, W1h 7et
Loft or dormer
Approved
May 2026
26/00330/FULL
20, Ranston Street, Nw1 6sy
Other householder work
Approved
Apr 2026
25/05135/FULL
8, Montagu Mews South, W1h 7er
How often householder applications are approved
Work
Bryanston & Dorset Square
Westminster
London
Typical decision time
All householder applications
67% (6)
83% (174)
80%
8 weeks
Loft or dormer
–
83% (18)
81%
10 weeks
Rear extension
–
73% (11)
79%
10 weeks
Two-storey extension
–
–
72%
8 weeks
Other householder work
60% (5)
84% (102)
70%
8 weeks
Side return or wrap-around
–
–
88%
8 weeks
Windows, doors or cladding
–
90% (20)
90%
6 weeks
Outbuilding or garden room
–
–
79%
8 weeks
Side extension
–
–
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 Bryanston & Dorset Square.
Move to a home 20 m² bigger (about £1,492,000)
Stamp duty on the new home
£92,950
Estate agent on yours 1.2% + VAT
£17,568
Solicitors, buying and selling
£3,000
Survey
£600
Removals
£1,500
Money gone
£115,618
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
−£163,200
Money gone
−£105,700
On these figures, extending loses about £221,318 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.
Other householder work
Approved
Aug 2025
25/04796/FULL
14, Upper Montagu Street, W1h 2pd
Other householder work
Approved
Oct 2025
25/04686/FULL
214, Edgware Road, W2 1dh
Other householder work
Refused
Jul 2025
25/03671/P3JPA
178, 180, Edgware Road, W2 2ds
Other householder work
Refused
Nov 2024
24/06598/P3JPA
63, Basement To First Floor Rear, Lisson Street, Nw1 5da
Other householder work
Approved
Sept 2024
24/05343/P3JPA
1b, Harewood Row, Nw1 6se
Other householder work
Approved
Jul 2024
24/02516/PIAPA
Street Record, Park West Place
Other householder work
Refused
Jul 2024
24/03543/P3JPA
6, Bendall Mews, Nw1 6sn
Other householder work
Withdrawn
Sept 2023
23/04106/PIAPA
65, Tresco House, Lisson Grove, Nw1 6uh
Other householder work
Approved
Jun 2023
23/02802/APA
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.