House Extension Architects in London
A well-planned extension is the most direct way to add space, light and value to your home. We design rear, side return, wraparound, two-storey and basement extensions across London and the South East — opening up kitchens and living spaces, improving the connection to the garden, and adding real square footage. As a RIBA Chartered Practice we manage the whole process, from first design to planning approval and construction.
Types of extension we design
Single-storey rear extensions are the most popular way to create open-plan kitchen and dining spaces; side return (side infill) extensions make use of the often-wasted alley beside Victorian and Edwardian terraces; wraparound extensions combine the two for a transformative ground floor; two-storey extensions add bedrooms and bathrooms above new living space; and basement extensions create high-value space below ground where above-ground options are limited. We test the options for your property and recommend the approach that best balances space, light, cost and planning risk.
Planning permission & permitted development
Some single-storey rear extensions can be built under permitted development — broadly up to 3 metres deep for terraced and semi-detached houses and 4 metres for detached houses, with a maximum height of 4 metres. Deeper single-storey rear extensions (up to 6 and 8 metres respectively) may be possible under the Larger Home Extension prior-approval process, which involves a neighbour consultation. Side, wraparound, two-storey and basement extensions, and any property in a conservation area or under an Article 4 Direction, generally require full planning permission. We establish the correct route and handle the application and any Certificate of Lawful Development.
Design, planning & delivery
We start with a measured survey and concept design, develop scaled drawings and 3D visuals, and prepare and submit the planning application with the supporting Design & Access Statement where required, responding to officer queries to protect your approval. After consent we produce building regulations drawings, coordinate structural engineering, drainage and party wall awards, and can manage the contractor and the build on site through to completion.
Recent house extensions
A selection of real, completed Shorplans projects.
Single Storey Side Extension
Sidcup, Kent
Basement & Rear Extension Scheme
Fulham, London
Frequently asked questions
How big can I build an extension without planning permission?
Single-storey rear extensions of roughly up to 3 metres (terraced/semi-detached) or 4 metres (detached) can often be built under permitted development, with deeper extensions possible under the Larger Home Extension prior-approval route. Side, wraparound, two-storey and basement extensions, and homes in conservation areas, normally need full permission. We confirm the position for your property first.
Do you handle the planning application as well as the design?
Yes. We prepare and submit the full application, produce the Design & Access Statement where it's required, and liaise directly with the local planning officer — responding to queries and, if needed, managing re-submissions or appeals. We hold a 97% planning approval success rate.
Will an extension need party wall agreements?
Often, yes — particularly for extensions close to or on a boundary, or for basements. We identify party wall matters early and coordinate the notices and awards with your neighbours so the build can proceed without delay.
Planning a house extension?
Tell us about your project and we'll send a free, no-obligation fee proposal tailored to your home and site.
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