A house extension can transform your home, adding valuable living space. Costs cover foundations, structural work, roofing, glazing, internal fit-out, and connection to existing services. In Mayfair (W1), costs reflect the area's Prime Central London market position, with a 25% premium over London averages.
Mayfair is London's most exclusive neighbourhood, home to world-class hotels, private members' clubs, and some of the most valuable residential real estate globally. Georgian townhouses and mews properties dominate.
| Specification | Price per sqm | Typical 25sqm Project | Includes |
|---|---|---|---|
|
Standard
Quality materials, clean design
|
£3,125 – £4,000 | £78,125 – £100,000 | All structural work, standard fixtures, full fit-out and decoration |
|
Premium
Designer brands, bespoke elements
|
£4,000 – £5,000 | £100,000 – £125,000 | Premium materials, designer fixtures, underfloor heating, smart controls |
|
Luxury
Finest materials, fully bespoke
|
£5,000 – £6,875 | £125,000 – £171,875 | Bespoke joinery, natural stone, top-tier appliances, architectural detailing |
Prices include VAT and are based on Mayfair (W1) market rates. Prime Central London pricing reflects the premium specification expectations and specialist requirements typical in this area. Actual costs depend on site-specific factors. All prices are guide estimates for 2025.
Here's what a typical 25sqm house extension project would cost in Mayfair at each specification level.
The Mayfair Conservation Area covers virtually the entire neighbourhood. Westminster City Council maintains strict controls on all alterations, with particular attention to Georgian facade preservation.
Key streets and roads in Mayfair include Mount Street, South Audley Street, Charles Street, Chesterfield Hill, Farm Street. Properties in these locations often have specific architectural characteristics that influence renovation costs, including ultra-premium specifications expected, Westminster strict planning controls, complex leasehold arrangements (Grosvenor Estate), restricted construction hours and methods, mews property access constraints.
Every house extension is unique. Let our RIBA chartered architects provide a detailed, no-obligation estimate tailored to your property and specification.
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