Home Extension Builders in Mayfair
Structural alteration in Mayfair W1J and W1K rarely goes outward, so Buildaway works within the envelope - reconfiguring, deepening and rebuilding instead.
Your Local Home Extension
Specialists in Mayfair
Searching for extension and structural specialists in Mayfair (W1J, W1K)? Buildaway
works across Mayfair - the townhouses around Grosvenor Square, Berkeley Square and
Mount Street, the buildings off Park Lane, Curzon Street and Hanover Square, and the
properties near Shepherd Market and Green Park.
Structural alteration in Mayfair rarely goes outward, so Buildaway works within the
envelope - reconfiguring, deepening and rebuilding instead. W1J and W1K stock is
largely listed and freehold-controlled, which makes consent and engineering the
project rather than an obstacle to it. Buildaway delivers to a specification that
matches the address, running structure, services and finish discreetly under one
contract with a programme that holds.
Our Home Extension Packages in Mayfair
Single-Storey Rear Extension
Ideal for expanding your living space. Includes structural survey, architectural drawings, groundworks and foundations, brickwork and roofing, bi-fold or sliding doors, heating installation, building regulation approval.
Side Return Extension (Most Popular)
Complete kitchen and living area transformation. Includes structural assessment, full groundworks, steelwork if required, brickwork and matching materials, glazing and doors, full insulation, electrics upgrade, flooring, building regulation approval, waste removal.
Double-Storey Extension
For those seeking maximum space addition. Includes architectural design, full structural alterations, steelwork and foundations, bespoke staircase, multiple room creation, bathroom or en-suite option, planning and building regulation handling.
Why Mayfair Homeowners Choose Buildaway
Discreet, expert teams with in-depth knowledge of Mayfair, Grosvenor Square, and London's luxury market
Based in your area with local expertise and reputation.
Bespoke extension designs for luxury apartments, penthomes, and period townhomes
We handle everything so you don't have to worry.
Transparent and honest pricing with no hidden fees or unexpected charges.
Clear upfront pricing with no surprises along the way.
Seamless, private project management with flawless delivery
Meticulous craftsmanship in every aspect of your extension.
Completed projects near Berkeley Square, Park Lane, and W1’s exclusive residential streets
Professional consultation and detailed quotes at no cost.
What's Included in Your Home Extensions Services
Everything you need for a seamless, stress-free home extension from structure to finish.
Full groundworks and structural build
Complete groundwork preparation and structural construction services.
Plumbing, electrics, and heating integration
Professional installation of all mechanical and electrical systems.
Roofing, windows, and external finish
Complete roofing, window installation and exterior finishing.
Plastering, flooring, and decorating
Professional plastering, flooring and decorating services.
Interior fit-out and finishing
Complete interior fit-out and professional finishing touches.
Project management and schedule control
Professional project management and timeline control throughout.
Latest Home Extension Insights
We publish detailed home extension guides and cost insights for homeowners across Mayfair and surrounding areas, helping customers plan projects with clarity before starting work.
Home Extension Cost in Mayfair
A local cost guide written specifically for Mayfair homeowners, with real figures for the area.
Home Extensions London: The Complete 2026 Guide
Everything from feasibility and planning to structure, cost and programme for a London extension.
Single-Storey Rear Extension Cost London
A realistic cost breakdown for the most common extension in London, with the variables that move it.
What Our Clients Say
Real reviews from our satisfied customers.
“It was an absolute pleasure working with Cormac and the Buildaway team. Greg is an absolute star. Cormac’s communication and advice was excellent, and the organisation and sourcing of additional materials was brilliant. A truly great team, I would thoroughly recommend Buildaway if you are after a stress free and top quality renovation.”
Sim Lewis
“From scoping to completion, Cormac was always very responsive, answering any questions we had on product selection and helped us source the products to get the best price. His team worked extremely hard and a big shoutout to Greg for his attention to detail! We couldn’t be happier with the results and would highly recommend Buildaway for any building project in the future…”
Georgina Ehmcke
“I am extremely impressed, happy and proud of what he and his team of Archie, Ben and Danny delivered. They all went beyond and far, I am very grateful for what they have done for me. I would 100% recommend Buildaway for any building, renovation etc - an excellent team with a good rapport, team spirit and working harmoniously together. Thank you Team Buildaway…”
Betty Lwanga
“The quality of the work, their high standards, and their professionalism, along with effective and proactive communication made a refreshing change from the builders I have used in the past. Even when we changed our minds and ideas during the job Cormac’s patience and support emphasised that he wanted to make sure that the finished product was exactly what we wanted…”
Michael Marks
“They were also very professional day to day - always tidy, and cleaned up really thoroughly when taking away all rubbish at the end. They stuck to the agreed timelines, and pricing was transparent throughout, with clear communication on any issues as they arose. Overall, I’m really pleased with the result and felt I could trust them throughout. I wouldn’t hesitate to recommend them…”
Sean Kelleher
“A great transformation of my bathroom into something modern and sleek. Cormac was professional to work with from the start and was very helpful in taking my ideas and sourcing products to fit the space and look aesthetically pleasing. I felt confident in working with the company as I could ask questions and I was also pleased to get suggestions and ideas…”
Vera Jajechnyk
Frequently Asked Questions
Your questions about home extensions in Mayfair, answered.
How much does a home extension cost in Mayfair?
Most Mayfair extensions land between £3,800–£5,000 and £5,000–£6,500, with double-storey schemes around Grosvenor Square and Mount Street reaching £95,000–£125,000. What people underestimate in W1J and W1K is below ground: foundations, drainage diversions and party-wall works are real cost before anything is visible. Buildaway prices them in, not after.
How long does a home extension take in Mayfair?
Twelve to twenty weeks on site for Mayfair, scheme depending. The build is the predictable part; Westminster City Council determination and party-wall awards are what stretch W1J and W1K projects. Buildaway handles both alongside design so the dates hold.
Do I need planning permission for an extension in Mayfair?
Assume it may. Mayfair extensions frequently run into conservation-area policy or listed-building consent, and W1J and W1K flats cannot use permitted development regardless. Buildaway resolves the Westminster City Council position first, because it determines what is worth drawing.
What types of extension do you offer in Mayfair?
We handle single-storey, side-return, wrap-around, double-storey and basement extensions throughout Mayfair. The right answer for your W1J and W1K property depends on drainage, boundary and Westminster City Council policy. Buildaway establishes those before proposing anything.
Do Buildaway handle both design and construction for Mayfair extensions?
We do the whole thing. Buildaway surveys your Mayfair property, designs a scheme that is genuinely consentable, secures approval from Westminster City Council, and builds it with our own team - one point of contact from feasibility around Grosvenor Square and Mount Street to sign-off.
Are your extension specialists local to Mayfair?
Yes. Buildaway works across Mayfair and the surrounding W1J and W1K streets regularly, so we know the plots around Grosvenor Square and Mount Street, the drainage runs, and what Westminster City Council has approved nearby. Local precedent is genuinely useful - knowing what got consented on the next street shapes a scheme that will pass.
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We Serve Mayfair and Surrounding Areas
Find us in the heart of Mayfair. We are proud to serve our local community.
Nearby Areas We Serve
Below are some of the local areas where you can find Buildaway transforming homes.
Ready to Transform Your Extension in Mayfair?
Buildaway specialises in stylish, durable designs that enhance prime London property value, with full discretion and premium attention to detail.