COUNTY HALL, LONDON
WATERPROOFING A HIGH-RISK LIFT PIT BELOW A HOTEL AND LEISURE SITE
SECTOR: Hospitality
SCOPE: Structural Diagnosis, Lift Pit Waterproofing, Retrofit
THE PROBLEM
Crownstone were instructed to investigate water ingress at the base of a lift pit beneath a commercial site at County Hall; a high-profile hospitality and leisure destination on London’s South Bank. Despite previous attempts at waterproofing, the lift pit was consistently filling with water, damaging lift equipment, breaching both safety, environmental and insurance compliance.
Set below high tide of the River Thames and in alluvium soil (soggy silt). A textbook high-risk environment for groundwater ingress, especially in a period property structure like a lift pit.
The lift shaft had been treated with a Type A cementitious system post-installation, but hydrostatic pressure had built up behind the waterproof layer, forcing it to bulge and fail. The result: deep contaminated water on the slab, corroded steel, and signs of salt deposits on the masonry.
THE PLAN
The survey team confirmed that, according to BS8102, the lift shaft should meet a Grade 2 environment, with no water penetration or dampness allowed. However, existing methods were fundamentally flawed: the lift pit required a Type C drained protection system that accepted and managed the inevitable ingress.
We proposed a comprehensive retrofit design using our Pitsafe™ system, tailored specifically for below-ground lift pits in high-risk environments. The aim was to create a water management system that actively prevents oil from mixing with water. The system waterproofs and manages water ingress while protecting against contamination, corrosion, and electrical failure.
CROWNSTONE’S SOLUTION
Our team installed a fully compliant Type C drained floor. This included a new sump below the lift pit floor, fitted with dual submersible pumps to manage risks of future water ingress, while a double-sealed chamber lid ensured oil from lift equipment couldn’t contaminate the drainage system.
The system included automatic fault detection with a secondary pump and mains-powered alarm providing backup in the event of primary pump failure. Surface-mounted pipework connected to the building’s foul sewer system, running discreetly through the adjacent electrical cupboard.
To meet lift industry standards, we also applied a protective cementitious barrierable to withstand 13bar of pressure, over the drainage system to capture any future oil escape and prevent environmental contamination.
A full maintenance programme was also designed and implemented, ensuring ongoing compliance and system longevity.
Our solution resolved a long-standing water ingress problem, restored compliance with BS8102, and ensured operational continuity in a busy commercial setting. The lift pit is now protected, manageable, and built to withstand the pressures of its riverside location.
