Unit 23, Battersea Business Centre
99-109 Lavender Hill
London SW11 5QL
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Get a free consultation today





    0207 228 1324 Get in touch via phone
    [email protected] Get in touch via email
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    Basement Architects in London

    Reimagining the spaces beneath your home.

    At Armstrong Simmonds Architects, we specialise in transforming underused basement levels into light-filled, elegant living areas. Whether you’re seeking to expand your home with an extra bedroom, family lounge, cinema room, or a spacious open-plan kitchen, our team brings vision, technical precision, and experience to every project in basement conversion London and basement extensions London. We understand that basements in London are more than just additional space — they are an opportunity to create something truly bespoke, with direct access to gardens, innovative glazing, and clever use of natural light.

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    Looking for Experienced Architects in London?

    Aside from providing you with a beautiful design, your architect needs to navigate complex
    planning and building laws that regulate the construction industry. Therefore, appointing a
    practice with the right amount of experience is the key to a smooth project delivery. Although
    not essential, appointing a RIBA chartered practice is also an important factor to consider.
    Being RIBA Chartered means that the practice must adhere to a code of conduct of
    professionalism and ethics which ensure quality control within the Architectural industry. The
    experience of the practice within London is another important factor to consider, particularly,
    as each borough has different modes of operation which can influence the design process.

    Whilst the National Planning Policy Framework (NPPF) provides the backbone for planning
    policy, each individual borough will have its own set of policy and guidance. A particular
    challenge within the borough of London is the planning process for basement design. For
    such a complex undertaking, stringent planning requirements must be met in the form of
    traffic reports, geology surveys and more. Another challenge is the added complexity of
    working with historic buildings. If your building is within a conservation area, a designated
    building of interest, or a listed building, any work to that building or surrounding area will be
    subject to strict requirements that are typically more rigorous than standard planning
    requirements. London Architects and designers must ensure their clients are advised
    appropriately on the process and that suitable consultants are appointed to conduct the
    necessary work.

    Get a free consultation today





      Why Choose a Basement Conversion

      Maximise space without expanding upwards.

      In many parts of Central and South West London, extending below ground is often the most effective way to increase square footage without altering the external footprint of your home. Whether your property is listed, in a conservation area, or faces planning constraints, a basement can provide valuable space while preserving the architectural character of your house. A London basement extension or basement conversions London can unlock the potential of your property and add significant value.

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      Natural Light, Seamless Design

      Our basement designs focus on creating liveable spaces that feel anything but underground. We prioritise the intelligent use of lightwells, internal courtyards, and full-height glazing to ensure rooms are bright and connected to the outdoors. These lower ground areas often open directly onto garden terraces, creating a seamless indoor-outdoor living experience. As experienced basement architects and a leading architect studio, we understand how to make the most of natural light and innovative design for every basement extension London project.

      From Concept to Completion

      As a RIBA Chartered Practice based in Battersea, we guide you through the entire process:

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      Initial Survey & Feasibility

      Assessing site potential, existing structure and planning context.

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      Concept & Scheme Design

      Developing ideas tailored to your vision and lifestyle, drawing on our expertise in architect for basement design.

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      Planning Applications

      Liaising with local councils, navigating permissions and regulations.

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      Technical Design

      Producing detailed construction drawings with structural coordination.

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      Tendering & Contractor Selection

      Recommending trusted local builders.

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      On-site Support

      Regular visits, contract administration, and quality control during construction.

      We work across all RIBA stages, delivering fully integrated basement projects that are functional, stylish, and highly tailored through our comprehensive architectural services. Our approach as a basement design studio and architect basement design experts ensures a smooth and transparent process.

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      How We Deliver Your Project

      We combine creative thinking with technical expertise to guide you through every stage of your project — from concept to completion. The process typically includes the following key phases.
      1

      Concept

      Briefing & Survey
      Armstrong Simmonds Architects will work with you to develop a concept design, sketching layout options to explore the potential of the property. We will also carry out a full measured survey of the property and its surroundings, allowing us to produce an accurate set of drawings.
      2

      Planning

      Application & Scheme Design
      Following on from the briefing we will prepare a set of scale drawings reflecting the range of ideas discussed. We will prepare and submit the planning application, liaising with the council as needed throughout the process. Our extensive experience will help facilitate a smooth planning process.
      3

      Visualisation

      3D Modelling Services
      To help you visualise the space in three dimensions we can produce internal and / or external views of your project. This can also be a useful tool to demonstrate the merits of the scheme to planners.
      4

      Technical

      Building Control and Detailing
      We will produce detailed technical drawings including drainage and electrical layouts, consulting with you to ensure the design meets your needs. We will then submit to building control and manage the approval process. As part of our architectural services during this process we can assist you in appointing other consultants, for example the structural engineer or party wall surveyor.
      5

      Specification

      Interior Architecture and Schedules
      We offer interior architecture and design for a high spec finish. We can produce further detailed information integrating specialist glazing components, floor finishes, joinery and bespoke staircase design as required.
      6

      Interior Design

      Furniture, Fittings & Equipment
      We provide Interior design architecture services ourselves or through collaboration with other London based Interior Designers, who may also be appointed by the client.
      We are happy to specify FF&E (furniture, fittings and equipment) for the project, providing a complete “one-stop” shop for your development.
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      Tendering

      Prices and Builders
      We will help you make an informed choice on an appropriate contractor. We maintain a selective tender list of contractors especially in the local London area, who we have experience working with on site. We will prepare tender documentation and appraise their quotes.
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      On Site

      Contract Administration
      Armstrong Simmonds Architects facilitates the implementation of the design by administrating a contract between you and the contractor. Amongst a wide array of architectural services, this will include undertaking site visits to monitor the quality of construction and handle any on-site queries from the contractor.
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      Our Expertise in London Basements

      With years of experience working in some of London’s most desirable boroughs, including Kensington, Chelsea, Clapham, Wandsworth and Fulham, we understand the local planning climate and technical challenges of basement construction. From complex site conditions to listed properties and tight urban plots — our team brings practical knowledge and design creativity to every brief. We provide bespoke solutions for London basement conversion and London basement extensions, tailored to each client’s needs.

      Customer
      reviews

      go to more reviews:
      Michael van Ree
      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.
      Linda Roberts
      Architects Armstrong Simmonds were appointed by us to turn our concept of open plan living into reality, which they did with extraordinary vision and design flair. The AS team listened carefully to our ideas and transformed an ordinary detached house into a breathtakingly beautiful home that offered light, space and a lifestyle that exactly reflected our needs and requirements. AS worked closely with us and our builder, and their focus to detail in the design and build was impressive. This young architectural practice in our opinion, offers something more. They listen, understand and are unique in their ability to conceptualise, plan and build with imagination, whilst considering aesthetics and functionality. Linda and Allan Roberts ...>>
      Rowena Carter
      I cannot recommend Armstrong and Simmonds architects highly enough. Within minutes of John meeting us at our home he had understood our brief and was sharing a vision that ticked all of our boxes.We had met with other architects who did not inspire us and told us the shape we wanted for our extension would not be possible. John had excellent knowledge of the local planning rules, researched planning submissions in the immediate area and was confident that he would get our application through - and he did! During the detailed design process John and his team listened closely to how we wanted to use the space. He came up with many design features and solutions to save costs and keep our dream design within our budget. Throughout the process they delivered an innovative plan that felt personal to us in a professional and timely manner. We found John and his team to be responsive, helpful and caring. They went above and beyond to get our project over the line and I have no hesitation in recommending the firm to anyone looking at home extension/improvement. We would not look anywhere else for any future builds! ...>>
      Rebecca Wheelhouse
      We had a fantastic experience with John and the team at Armstrong Simmonds. We have a beautiful home and would happily use them for our next project.... hopefully even bigger next time! Flawless from beginning to end, I thoroughly recommend them.

      Start Your Basement Journey

      If you’re considering a basement project in London, we’d love to hear from you. Whether you have a clear idea or are just exploring possibilities, our team will help you unlock the full potential beneath your home. We can advise on the cost of basement conversion London and support you from initial concept to completion.

      Contact us today to arrange a consultation
      0207 228 1324 Get in touch via phone
      [email protected] Get in touch via email
      Armstrong Simmonds Architects Ltd
      Unit 23, Battersea Business Centre,
      99-109 Lavender Hill, London, SW11 5QL

      Get a free consultation today





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        Explore More of What We Do

        We offer a wide range of architectural solutions - explore more of what we can help you with.