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Bespoke House Extensions That Add Space, Light and Lasting Value
At Armstrong Simmonds Architects, we design bespoke house extensions for homes across London. Whether you are planning a light-filled rear extension, a side return, a wrap around or a full double storey addition, we create tailored solutions that make the most of your home’s footprint, complement its character, and stand the test of time. Founded in 2010 and RIBA Chartered Architects, our Battersea studio has guided homeowners through every stage of their extension, from first sketch to finished space.
Aside from a beautiful design, your architect must navigate the complex planning laws that regulate the construction industry, so appointing a practice with the right experience is the key to a smooth project delivery. Choosing a RIBA Chartered practice matters too, as it means the practice follows a strict code of professional conduct and ethics that safeguards quality throughout.
Local knowledge matters just as much. Whilst the National Planning Policy Framework (NPPF) provides the backbone for planning policy, each London borough has its own guidance. Having designed house extensions across Central, South-West, West and North-West London since 2010, we understand how to approach a period terrace, a semi-detached home or a listed building with the sensitivity it deserves.
Our portfolio includes a range of kitchen-focused side return extensions in London, from compact interventions in Victorian terraces to larger open-plan transformations. Each project is developed with a focus on spatial clarity, light and long-term usability.
A well-designed house extension is one of the most effective ways to add space and improve how your home works, without the cost and upheaval of moving. Extending towards the garden or into a side return lets us reimagine your ground floor with an open-plan kitchen, dining zone or a versatile family space filled with daylight.
With space at a premium across London, a considered extension offers flexibility and a real uplift in value. From a modest three metre rear extension to a modern addition on a period home, we tailor every scheme to your brief, your budget and your lifestyle.
No two extensions are alike. Our portfolio ranges from contemporary additions in glass to traditional brick-built designs that blend with period façades. The house extension types we design most often include:
We work with contemporary glazing, bespoke joinery and materials chosen to suit your brief and budget, whether you favour a modern extension on an older house or a design that sits quietly within a conservation area. An extension can also form part of a wider house renovation.
From our Battersea studio, we offer a complete architectural service tailored to each house extension:
Concept & Feasibility. We understand your aims and survey the site, exploring house extension design options that make the most of space, natural light and flow.
Planning & Permissions. We prepare the drawings and plans and submit your planning application, liaising with the local authority to give the scheme its best chance of approval.
Design Development. We refine the details, from glazing and rooflights to sliding doors and landscaping, for a cohesive indoor-outdoor space.
Technical Design. We produce technical drawings and coordinate with structural engineers to deliver a complete building control package.
On-Site Support. We administer the contract, carry out site visits and oversee the build so your extension is delivered as intended.
The cost of a house extension in London depends on its size, structural complexity, level of finish and property type, so we provide a tailored estimate once we understand your brief rather than a one-size-fits-all figure. Investing in considered design early on helps you control costs and avoid expensive changes later.
Many single storey rear and side extensions can be delivered under permitted development, whilst larger schemes, flats and homes in conservation areas or listed buildings usually require planning permission. We assess exactly what your project needs at the outset and advise you clearly. Where specialist consultants are required, such as a structural engineer or party wall surveyor, we can help you appoint them.
As a RIBA Chartered practice with a strong portfolio of residential work, Armstrong Simmonds Architects is well regarded amongst homeowners across London. We combine creative thinking, technical precision and deep local knowledge to deliver house extensions that are as functional as they are enduring.
We are glad we found Armstrong Simmonds Architects to help us on our first project. We had bought a run-down terraced house near Clapham Common with the goal of extending and refurbing to increase value. John initially impressed us by first listening carefully to what we wanted to do, then showing us creative ways to achieve the results and finish we were looking for.
Safe to say we certainly have managed that and both John and Alan have been instrumental in doing so. The guidance and consideration at every step have exceeded our expectations and Alan’s attention to detail during the build has been critical for the high standards we have set for this project.
They have provided us with a service which reflects every stage of the design and build. Starting with the initial drawings, schedule of works, tendering and interior design. We also employed ASA for Contract Administration to be the key middle-man between us and the builder, which they were happy to help.
We are now underway with our second project with ASA and they have been able to deliver the final drawings for planning within a fairly tight time frame, without hindering on quality. I know the whole team worked hard to help bring our vision to life and it’s been brilliant working with them over the last 18 months. They have shown a great ability to solve any issues that arose quickly and are able to communicate effectively with different contractors at all levels. I have no doubt the next redevelopment project will go well.
We chose Alan and John for our extensive project and incredibly pleased with that choice and the result. We have a Victorian terraced house and wanted to do a classic loft conversion and ground floor extension. The Armstrong Simmonds team provided a vision which achieved our goals, but with a design we could have never have thought of ourselves which we love. We used them from start to finish and are incredibly glad we did. Alan supported us through the tender and renovation processes, and we are incredibly pleased with the end-product and the quality of work of builder Cezar of Vecchini. We would highly recommend Armstrong Simmonds for their vision, design thoughtfulness and exceptional assistance through the project. Thanks team!
We worked with Alan and the team from Armstrong Simmonds for 3 years from start to finish to achieve the full renovation of a London townhouse. It was a challenging brief given the nature of the property but collectively what has been achieved is an outstanding end result. Alan and John thoughtfully incorporated our vision with the realities of converting an old Victorian house and the scrupulous attention to detail, symmetry and balance achieved in the design were instrumental in us choosing Armstrong Simmonds in the first place.
In addition Alan supported us through the tender and during the renovation working with our excellent builder Cezar of Vecchini to deliver the brief. I would highly recommend if you are looking for a team to turning your vision to the end product with a very high attention to detail while still being good humoured and a generally great guy to work with. Thanks again team. Dom and Kamilla
John and his team have been brilliant to work with for our full house renovation and extension in SW London. Our house is quite unique and that combined with it being in a conservation area we knew it wouldn’t be a straight forward planning process – but Armstrong Simmonds did a fantastic job and helped us navigate us through every step. We couldn’t be happier with the detailed design and outcome.
If you are thinking about a house extension in London, we are here to guide you. Whether you have a clear vision or are still exploring, let’s unlock the potential of your home together.
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Architect's studio/ House Extension Architects in London
