Service
Basement Conversions in London
Converting and extending London’s lower-ground space — engineered, waterproofed and detailed properly, because basements forgive nothing.
Completed basement — media room, kitchen or family space
Space where London has run out of it
Where lofts and gardens are exhausted, the basement is what remains — and in high-value streets it is often the most cost-effective space a house can gain. Projects range from converting an existing cellar or lower-ground floor to full excavation beneath the house and garden.
This is unforgiving work. Structure, underpinning, drainage, and above all waterproofing must be designed — not improvised — and built by people who do it repeatedly. We engineer every basement with a structural engineer and a waterproofing design that carries a real warranty.
Light and ceiling height decide whether a basement feels like the best room in the house or a converted cellar: light wells, courtyards and generous stair openings are where the design effort goes. Basements often anchor a whole-house renovation.
What's included
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Feasibility & engineering
Ground conditions, neighbouring structures and a realistic budget before commitment.
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Excavation & underpinning
Sequenced underpinning and excavation, monitored throughout.
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Waterproofing design
Designed waterproofing systems with warranties — not a single coat of tanking slurry.
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Light wells & glazing
Front and rear light wells, courtyards and structural glazing for natural light.
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Services & ventilation
Drainage pumps, heating, ventilation and electrics designed for below-ground use.
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Fit-out & finishing
From cinema rooms to kitchens to self-contained flats, finished to house standard.
What does a basement conversion involve — and cost?
Basements are the most engineering-heavy residential work there is, and cost reflects ground conditions, depth and area more than finish. Planning permission is required for excavation, and party wall agreements with neighbours are almost always needed — we manage both.
Read the guide: basement conversion costs in London.
Basement conversion FAQs
Is my house suitable for a basement?
Most London houses can technically be excavated; the real questions are ground conditions, water table, neighbouring structures and whether the value gained justifies the cost. Our feasibility stage answers those before you spend seriously.
How long does a basement take?
Converting an existing cellar can take three to four months; a full excavation typically runs six to twelve months depending on size. We phase the noisiest work and agree working hours with neighbours up front.
Will it be dry — permanently?
A properly designed system with maintained drainage should keep a basement dry for its lifetime. That is why we insist on designed waterproofing with a warranty rather than a builder’s tanking job.
Thinking about going down?
Book a consultation and we’ll assess feasibility honestly — ground, neighbours, budget and value.
Book a Consultation