Following a review of the available geotechnical and structural information, SPEEDECK identified that traditional shallow foundations would present risks due to ground variability and anticipated settlement. A CFA piled raft foundation was therefore recommended as the most technically reliable and efficient solution. By integrating piling and reinforced concrete raft slabs into a single substructure system, the approach simplified construction logistics while reducing the number of trade interfaces. This integrated design strategy enabled consistent load transfer into the underlying strata while maintaining programme reliability across the large residential scheme.
Concept Design
Design Engineering
The substructure solution incorporated reinforced concrete raft slabs of 225 mm thickness beneath the two-storey housing plots and 300 mm beneath the apartment block, reflecting the differing structural load requirements across the development. Heave protection was incorporated where required, including 160 mm voidformers beneath plots influenced by shrinkable clay conditions, ensuring long-term durability of the foundations. The CFA pile design achieved a maximum safe working load of 490 kN. The development required a total raft slab area of approximately 1,741 m². The engineering strategy balanced structural performance with efficient pile spacing and reinforcement optimisation, delivering a technically robust and warranty-compliant design.
Construction
SPEEDECK delivered the piling, drainage and raft installation as a single coordinated package of substructure works, significantly simplifying sequencing on site. The site was located deep in a residential area, with logistical and access constraints, so forward planning was essential.
The integrated approach reduced reliance on multiple subcontract trades and facilitated efficient installation of drainage and underslab services. This streamlined construction methodology created a safe and consistent working platform for the superstructure works while maintaining programme certainty across the multi-phase residential development.
