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.

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.
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.

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.
As a RIBA Chartered Practice based in Battersea, we guide you through the entire process:
Assessing site potential, existing structure and planning context.
Developing ideas tailored to your vision and lifestyle, drawing on our expertise in architect for basement design.
Liaising with local councils, navigating permissions and regulations.
Producing detailed construction drawings with structural coordination.
Recommending trusted local builders.
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.

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.
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.

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