Home Extension Builders in Westminster
Extending in Westminster SW1A and SW1P usually means working inside the existing envelope, so Buildaway reconfigures structure to find the space.
Your Local Home Extension
Specialists in Westminster
Looking for extension specialists in Westminster (SW1A, SW1P)? Buildaway works
throughout SW1 - the buildings around Smith Square, Horseferry Road and Millbank,
the properties near St James's Park and Victoria Street, and the streets behind
Whitehall, Westminster Abbey and the Houses of Parliament.
Extending in Westminster usually means working inside the existing envelope, so
Buildaway reconfigures structure to find the space. SW1A and SW1P sit under the
tightest planning control in the country, with listed fabric, security constraints
and restricted access shaping every decision. Buildaway holds design, consents,
structure and finishing under one contract, working to the agreed hours and keeping
the Westminster programme on the dates we committed to.
Our Home Extension Packages in Westminster
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 Westminster Homeowners Choose Buildaway
Local teams trusted across Westminster, St James's, Belgravia, and Central London
Based in your area with local expertise and reputation.
Bespoke extension designs for heritage buildings, luxury developments, and investment properties
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.
Full project management for a seamless, stress-free experience
Meticulous craftsmanship in every aspect of your extension.
Completed projects near Westminster Abbey, Victoria Street, Horseferry Road, and SW1 postcodes
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 Westminster and surrounding areas, helping customers plan projects with clarity before starting work.
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.
Planning Permission for Home Extensions
When you need permission, when permitted development covers you, and how to avoid a refusal.
What Our Clients Say
Real reviews from our satisfied customers.
“The team turned up when they said they would and kept the house tidy each day, which made a big difference while we were living in the property during the works. The quality of the finish is excellent. The bathroom looks fantastic and the bedrooms feel completely refreshed. We wouldn’t hesitate to recommend Cormac and the Buildaway team…”
Helen Sivyer
“From my first contact with Cormac, I was in good hands. His team turned my vision into reality, communicating with me every step of the way and offered helpful suggestions which turned my bathroom into an oasis. I could not be happier and would highly recommend their services. Thank you to the team of Buildaway Construction Ltd…”
Jackie Brown
“I was recommended Buildaway by a colleague as I was impressed by the work they had done for my colleague. From the moment I contacted Cormac, I knew I was in good hands. He was incredibly friendly and accommodating right from the start. The very next day, he was at my property, taking measurements and discussing design options. What really impressed me was Cormac's honesty…”
Nana A.
“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
“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
“We’ve had a genuinely fantastic experience with Buildaway. Cormac was ultra responsive and excellent at communicating with us throughout our project. The quality of the work was excellent - so much so, that we extended our project by adding a range of other building renovations to our original ask, each completed with care and precision…”
Kiran Collier
Frequently Asked Questions
Your questions about home extensions in Westminster, answered.
How much does a home extension cost in Westminster?
Most Westminster extensions land between £40,000–£60,000 and £60,000–£80,000, with double-storey schemes around Smith Square and Millbank reaching £100,000+. What people underestimate in SW1A and SW1P 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 Westminster?
Twelve to twenty weeks on site for Westminster, scheme depending. The build is the predictable part; Westminster City Council determination and party-wall awards are what stretch SW1A and SW1P projects. Buildaway handles both alongside design so the dates hold.
Do I need planning permission for an extension in Westminster?
It depends on your SW1A and SW1P property. Permitted development covers a good number of Westminster rear extensions, but if you are listed, in a conservation area, or leasehold, the answer changes and Westminster City Council consent is needed. Buildaway confirms what is achievable at feasibility rather than designing something that gets refused.
What types of extension do you offer in Westminster?
We handle single-storey, side-return, wrap-around, double-storey and basement extensions throughout Westminster. The right answer for your SW1A and SW1P property depends on drainage, boundary and Westminster City Council policy. Buildaway establishes those before proposing anything.
Do Buildaway handle both design and construction for Westminster extensions?
Both, on one contract. For Westminster clients Buildaway handles drawings, structural engineering, consents and construction. Splitting design from build is where SW1A and SW1P extension projects most often lose money, because the gap between them is nobody's problem until it is yours.
Are your extension specialists local to Westminster?
We are in Westminster constantly. Buildaway knows SW1A and SW1P property: the boundaries, the ground conditions, and how Westminster City Council treats rear additions here. That experience makes our feasibility advice reliable rather than optimistic.
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We Serve Westminster and Surrounding Areas
Find us in the heart of Westminster. We are proud to serve our local community.
Ready to Transform Your Extension in Westminster?
With landmark views and unrivalled property values, Westminster demands the highest standards - Buildaway combines expert craftsmanship with luxury design to elevate homes in one of London’s most prestigious locations.