For London’s finest streets
Large & luxury house extensions
Design-led double-storey schemes, basements and whole-house transformations for the finest streets in London and Hertfordshire. Fixed price, planning handled, one team from drawings to handover. Projects from £150,000.
How this market buys
Certainty is the luxury
At this end of the market nobody is shopping for the cheapest quote. They are buying confidence that the number is real, the site is quiet and one person answers for everything.
The number you sign is the number you pay
A fixed, itemised proposal, line by line, VAT stated. Not an estimate that grows.
One point of contact
A dedicated project lead from first visit to handover, so one person answers for everything.
A quiet, respectful site
Tidy hoarding, managed deliveries, neighbours informed before we start. Your street stays your street.
Design-led planning
Approvals at this level are won on proportion, materials and landscaping. We submit schemes composed to pass.
What we build at this level
Projects sized for the plot, not the postcode average
Houses on these streets are large and the briefs match: structural glazing, second storeys, floors below ground. Every project is priced on its design and quoted as one fixed, itemised figure. If you want to gauge budgets before we talk, the honest numbers live in the luxury extension cost guide.
Whole-house transformation
Extension plus full internal reconfiguration in one programme. What most £150,000-plus briefs actually are: the house rethought, not just enlarged.
Double-storey extension
Bedrooms and bathrooms above, open living below. The scheme that changes what the house is, not just its footprint.
Basement leisure floor
Gym, cinema or guest suite below ground without changing how the house presents to the street. Serious engineering, properly managed.
Wrap-around extension
Side and rear combined. Generous plots carry a wrap-around without crowding the boundaries.
Large glazed rear
Slim-framed sliders or full structural glazing opening the back of the house to the garden. The signature scheme of the premium postcodes.
Annexe or garden building
A fully serviced second building: multigenerational living, staff or guest space, or a serious garden office.
Where we do it
London’s finest streets, area by area
Each area guide covers the housing stock street by street, what the local council is approving right now and honest 2026 costs, written for the scale of project these postcodes actually commission.
Large projects travel: if your street is not listed here, ask us anyway.
The knowledge
Guides for complicated postcodes
How much does a luxury extension cost in 2026?
Honest banding from £150,000 to £500,000 and beyond, and what actually drives each band.
Extending in the green belt
Arkley, Totteridge and the Hertfordshire villages share one rulebook. How the proportion test works and how to design for it.
The Hampstead Garden Suburb Trust, explained
Why the Suburb needs two consents, what the Trust looks for, and how we run both applications.
Extending in a conservation area
What the designation really changes, and the design moves that win consent on protected streets.
The Party Wall Act on premium streets
Notices, surveyors and neighbours handled properly, so the boundary never delays the build.
Architect or design-and-build?
The honest comparison for large projects, including where the other route genuinely wins.
Extension planning fees, explained
Every fee on the road to consent, itemised, so nothing on the planning side surprises you.
Questions, answered
Luxury extension FAQs
What counts as a luxury extension?
Scale and finish rather than any single feature. In practice it means projects from £150,000 upwards: double-storey schemes, basements, wrap-arounds and whole-house transformations, finished with structural glazing, bespoke joinery and stone at a specification the house deserves.
How much does a luxury house extension cost in London?
Honestly: it depends on the design, which is why we quote each project as one fixed, itemised figure after a design visit. Most projects we take on start around £150,000, and our luxury extension cost guide sets out the realistic banding and what drives it.
Which areas do you cover for large projects?
London’s finest streets and the Hertfordshire border: Hadley Wood, Totteridge, Arkley, Hampstead, Highgate, Muswell Hill, Mill Hill, Brookmans Park, Cuffley, Chigwell and Loughton among them, all served from our base in Cockfosters. If your postcode sits nearby, ask: large projects travel further.
Do you handle planning for green belt and conservation areas?
Yes. Many of these areas sit under a protective layer: green belt around Arkley and Totteridge, conservation areas in Highgate and Monken Hadley, and the Trust regime in Hampstead Garden Suburb. We design for the constraint from day one and manage every application to the decision notice.
Is the price really fixed?
Yes. After the design visit you receive an itemised, line-by-line proposal with VAT stated, and that is the figure you pay. Changes only happen when you choose to change the scope, and they are priced and agreed in writing before any work proceeds.
Find out what your plot could carry
A private design visit, an honest conversation about feasibility and budget, then a fixed, itemised proposal. No obligation, no pressure.
Or call us: 020 3051 9430