For detailed information on process, pricing tiers, technical specifications, and FAQs, see our comprehensive basement conversions guide.
View Full Basement Conversions Guide →Basement work in Central London is where design ambition meets structural discipline. These projects can unlock a full extra floor for family rooms, guest suites, gyms, utility space, wine storage or staff accommodation without changing the street-facing appearance of the property.
They are also the most technical residential projects we deliver. Across Central London, listed building consent, leasehold approvals, conservation controls and premium neighbour sensitivities combine with neighbour impact, waterproofing strategy, sequencing and temporary works to make early engineering input essential.
We manage basement feasibility, planning, structural design, excavation and fit-out across Marylebone, Mayfair, Belgravia, and Knightsbridge and the wider Central London region, so the commercial scope stays grounded in what is realistically buildable.
The right basement type depends on your existing foundations, soil conditions, budget and the amount of space you need.
Converting an existing cellar by lowering the floor level, waterproofing the structure, installing ventilation and fitting out as habitable space. The most cost-effective option.
Excavating an entirely new basement level. Involves mass excavation, sequential underpinning, reinforced concrete slab, full waterproofing and mechanical ventilation. Maximum space and ceiling height.
Double or triple-depth excavation creating multiple subterranean floors — often extending beneath the garden. For pools, cinemas, wine cellars, gyms and plant rooms.
Basement construction follows a strict engineering sequence. Every phase depends on the one before it.
We commission geotechnical bore holes to determine soil type, bearing capacity, water table depth and contamination risk. Our structural engineers review existing foundations and party wall conditions. Our architects assess spatial potential, light well options and staircase positions. You receive a comprehensive feasibility report with a fixed-price quotation covering the entire project.
Architects produce the basement layout, engineers design underpinning sequences and waterproofing specs. We submit planning applications, building regulations drawings and party wall notices in parallel. Most boroughs now require a Basement Impact Assessment addressing hydrology, structural monitoring and construction logistics — we prepare the full BIA.
Foundations are underpinned in careful sequence — never more than one metre at a time — using mass concrete pours. Soil is removed by conveyor belt, typically 6–10 lorry loads per day. We install monitoring systems (crack gauges, level surveys) on your property and neighbours throughout. Once fully underpinned, the reinforced concrete floor slab is poured.
Waterproofing system installed — Type A (barrier), B (structurally integral) or C (drained cavity) depending on conditions. Sump pumps with battery backup installed where required. Light wells constructed to bring natural daylight below ground. Mechanical ventilation (MVHR) installed for habitable-room air quality.
Insulation, plasterboarding, electrics, plumbing, staircase, bathroom fit-out, flooring, joinery and decoration. For luxury basements: cinema acoustic treatment, wine cellar climate control, gym flooring, pool tiling and plant rooms. Building control sign-off, completion certificate and handover with 10-year structural and waterproofing warranty.
Guide prices per sqm for complete basement conversions. All prices include design, engineering, excavation, waterproofing, fit-out and decoration.
Basement construction demands specialist engineering rigour and coordination.
Underpinning sequences, reinforced concrete design, temporary works and monitoring — all designed by our own engineering team, not outsourced to external consultants.
Every basement carries a 10-year warranty on structural and waterproofing systems, backed by an independent insurance-backed guarantee. We install the waterproofing ourselves.
Our fixed-price includes a soil investigation before pricing — no hidden ground condition surprises. If we encounter unexpected conditions, that's our risk, not yours.
Full BIA preparation covering hydrology, construction methodology, monitoring strategy and traffic management for all London boroughs.
RICS surveyors manage all notices, schedules and monitoring. Basement party wall agreements are complex — our experience accelerates the process.
Front, rear and internal light wells including glazed walkways and courtyard wells — transforming basements from dark cellars to bright living spaces.
Real-time crack gauges, level surveys and vibration monitors on your property and neighbours throughout excavation and underpinning.
Skip lorry scheduling, route planning, highway licences and disposal to licensed sites — typically 6–10 loads per day during excavation.
MVHR systems designed to meet Building Regulations Part F for habitable rooms — fresh air circulation and humidity control below ground.
Specialist plumbing including macerators or pumped drainage where gravity drainage to the sewer isn't available at basement level.
Acoustic isolation for cinemas, climate-controlled wine storage, sprung gym flooring, pool tiling and plant room design.
Selected basement conversions completed across London.
Full dig-down creating living room, utility and bathroom with front light well. Planning approved in conservation area.
Existing cellar deepened to create wine room, home office and WC. Sensitive approach to listed fabric with lime-based waterproofing.
Two-level basement with cinema, gym, spa, 12m pool and plant room extending beneath the rear garden.
Need a same-day repair or maintenance visit in NW London?
Visit Hampstead On Demand →The soil investigation before quoting made all the difference. Other companies quoted blind and hit us with variations for unexpected ground conditions. Hampstead Renovations did bore holes first, priced accordingly and delivered exactly on budget. The light well brings so much daylight that visitors don't realise they're underground.
Converting our Victorian cellar was far more complex than anticipated — but the team handled every challenge without drama. The party wall process with three neighbours was managed seamlessly, the waterproofing is flawless and we now have a proper home office and guest bedroom where we used to store bicycles.
Our double basement in Highgate was the single largest project we've ever undertaken. The engineering precision during underpinning — monitoring every millimetre of movement — gave us complete confidence. The cinema acoustics are extraordinary and the pool area feels like a five-star spa.
Common questions about basement excavation, engineering and construction in London.
Use the area pages below to jump straight to the streets, councils and property types most relevant to your project.
Basement excavation, underpinning and lower-ground fit-outs for mansion flats, Georgian townhouses and medical-quarter apartments.
Basement excavation, underpinning and lower-ground fit-outs for premium apartments, lateral reconfigurations and heritage-led interiors.
Basement excavation, underpinning and lower-ground fit-outs for grand stucco houses, mews properties and basement-heavy schemes.
Basement excavation, underpinning and lower-ground fit-outs for luxury apartments, townhouses and high-spec fit-outs.
Basement excavation, underpinning and lower-ground fit-outs for listed terraces, institutional-grade approvals and complex party-wall contexts.
Basement excavation, underpinning and lower-ground fit-outs for stucco terraces, lower-ground homes and compact townhouse footprints.
Book a free consultation to discuss your central london project. We will assess feasibility, planning context, likely budget and the most efficient route from design to construction.
We survey your property, assess feasibility and provide an honest appraisal — completely free, no obligation.
Book Basement SurveyGuide prices including VAT. Final costs depend on specification and site conditions.