Ground investigation revealed Made Ground overlying London Clay, with a high volume change potential and shallow groundwater. Traditional shallow foundations were ruled out due to heave risks and tree influence zones. Following review of alternative methods, SPEEDECK recommended a Continuous Flight Auger (CFA) piled raft solution, providing both structural efficiency and long-term stability. This eliminated the need for multiple subcontract trades, offering the client a streamlined and accountable foundation package.
Concept Design
Design Engineering
SPEEDECK’s design centred on a 225mm reinforced concrete raft slab with 225mm voidformers to protect against ground heave. Using Eurocode-compliant calculations, piles were designed to carry safe working loads of up to 230kN, with pile lengths ranging from 6.0m to 8.5m.
The solution supported a total raft area of 423m², removing the need for ground beams, substructure brickwork, and precast flooring. This reduced complexity, accelerated programme delivery, and ensured full compliance with NHBC and warranty provider requirements.
Construction
SPEEDECK managed the complete foundation package, including piling, integrity testing, underslab drainage, reinforcement fixing, and raft construction. A lightweight piling rig was used, removing the need for an engineered piling mat. Voided raft construction addressed heave risks, while single-team delivery streamlined site coordination.
The works were completed within a 6-week programme, ensuring timely handover and smooth progression to superstructure.
