Service · Basement Construction
Single-storey, double-storey and lightwell basement excavations under existing London homes.
Overview
Basement construction under existing London townhouses, semi-detached and detached homes is high-margin, technically demanding work that HXL routinely delivers. Single-storey excavations under footprint, double-storey schemes, lightwell and sub-pavement vault construction in conservation-area streets. All schemes include temporary-works design, structural propping, BS 8102-compliant waterproofing, and party wall coordination across all affected neighbours.
How we deliver
The basement construction process.
01
Survey & design
Ground investigation, structural engineering design, party wall service, planning consent where the scheme falls outside permitted development.
02
Excavation
Underpin, install temporary works, excavate, remove spoil, construct retaining walls.
03
Waterproofing & fit-out
BS 8102 system installation, M&E first fix, plant install, second fix and finishes.
04
Sign-off
Structural sign-off, Building Control completion, waterproofing system warranty, 12-month workmanship warranty.
Questions
What clients ask about basement construction.
Single-storey under footprint: £500k to £900k. Double-storey or lightwell: £900k to £1.5m+. Costs depend on access, ground conditions, party wall scope and finish specification.
Across NW3 Hampstead, NW8 St John's Wood, W11 Notting Hill, W8 Kensington, SW3 Chelsea, N6 Highgate, and the surrounding prime-fringe boroughs. Conservation-area and Article 4 streets handled as a matter of course.
Most full basements need a planning application. Permitted development applies only to limited cases. Hampstead, Chelsea and Kensington have additional basement restrictions which we handle as part of the application.
Yes. Every basement scheme involves Party Wall Act service across the affected neighbours. We coordinate surveyor appointments and awards as part of the main contract.
Other services
The rest of HXL's capability.
Planning Coordination
Planning submissions, approvals and consents. Handled in-house alongside your architect.
Architect Partnership
Appointed as principal contractor for architect-led schemes. Drawings are the brief.
Structural & Engineering
Structural, MEP, acoustic and sustainability consultants. Procured and coordinated as part of one contract.
Enquire
Tell us the project in a paragraph. We reply within one working day.
HXL takes on a selective number of projects each year. A short note with the site, scope, appointed architect (if any) and likely timescale is all we need to open a conversation.
Private Residential
Homeowners with projects from £500k to £3m+, London and the Home Counties.
Residential Developments
Blocks of flats, multi-unit schemes, resale-ready delivery.
Heritage & Period
Listed buildings, conservation areas, period townhouses.