Having the Beams team on hand to manage the project and provide extra reassurance on build decisions was incredibly helpful and made the whole experience stress free.
Kerry
London
They have been extremely efficient and reassuring. It was a complex project but they took it all in their stride. They recommended very good contractors who were all punctual, polite and capable.
Andrew
London
All about trust. I felt comfortable with my money, my project, and my home knowing that the outcome would be to my satisfaction or would be made good.
Chris
London
Lambeth's basement conversion experts
Many Lambeth terraces around Clapham, Kennington and Stockwell already have a cellar or shallow basement that can be converted into proper living space. Others need a new excavation. Either way, our vetted builders specialise in the structural and waterproofing work a basement demands, and Beams keeps design, planning and build under one fixed-price contract.
Cellar conversion, basement conversion or new basement?
Cellar conversion: Upgrading an existing cellar into usable, habitable space.
Basement lowering: Digging down to create full head height in an existing basement.
New basement excavation: Building an entirely new basement beneath a home that does not have one.
How basements are waterproofed
Every basement conversion follows BS 8102, the British Standard for waterproofing below ground, using a combination of tanking, cavity drain membranes and, where needed, external drainage. Getting this right from the design stage is what keeps a basement dry for decades rather than years.
What your Lambeth basement could become
A home cinema, a guest suite, a gym, a self-contained flat for rental income, or simply extra living space to relieve a busy household. On the terraced streets around Brixton and Clapham, a basement is often the only way to add significant space without touching the garden.
What a basement conversion costs in Lambeth
Basement work is priced on the scope of excavation, waterproofing and structural support required. Based on Beams estimates for London basement conversion projects, here is a general guide:
Project type | Typical estimate |
|---|---|
Lower end | £90,000 |
Most projects | £150,000 |
Larger or higher spec | £220,000 |
Top 10% of projects | £350,000 |
These are estimate ranges rather than fixed quotes. Converting an existing cellar sits at the lower end, while a full new excavation under the footprint of the house pushes it higher. Your fixed price is confirmed once ground conditions and the design are assessed.
How a Beams basement conversion works
1. Free first call: Tell us about your home and what you want the space for.
2. Design, surveys and planning: Structural and ground surveys inform the design and any application.
3. Fixed-price build: A vetted specialist builder delivers it under contract, with milestone payments.
Why a basement conversion is worth it
In dense inner London, a basement is often the only realistic way to add a substantial amount of floor space without extending the footprint of the house. Done properly, it adds genuine living space and real resale value.
Converting a basement in Lambeth
Lambeth's Victorian and Georgian terraces around Clapham, Kennington and Stockwell frequently have cellars that were built as coal stores or basic storage, ideal candidates for conversion. Lambeth has more than 60 conservation areas, including Kennington, Albert Square, Clapham Old Town and Vauxhall, and basement work here typically needs full planning permission, alongside Building Regulations approval and, on terraced or semi-detached streets, a party wall agreement with neighbours. Streatham, the borough's southern neighbourhood, is covered by its own dedicated Beams pages.
With the average Lambeth home selling for around £537,000 in the year to July 2026 (ONS/HM Land Registry, provisional), a well-executed basement conversion is a significant way to add space and value in a borough where land is scarce. We also work with homeowners across the nearby boroughs of Southwark and Wandsworth.
Other services in Lambeth
We also help Lambeth homeowners with:
Bathroom renovation in Lambeth
Basement conversion in nearby areas:
Basement conversion in Streatham
Ready to convert your Lambeth basement?
Get a free estimate and take the first step. No commitment, no sales pressure.