Church Road, Steep Residential Development

Following a detailed geotechnical review, SPEEDECK recommended a Continuous Flight Auger (CFA) piled raft foundation system across the development. This approach efficiently transfers building loads through the weaker upper clay strata and into deeper competent material.

Due to the presence of high volume change potential clay soils within the upper ground profile, heave protection measures were incorporated into the design. Voidformers were introduced beneath the raft slab to accommodate potential ground movement and reduce the risk of uplift forces acting on the structure. This concept provided a cost-effective and warranty-compliant solution suited to the challenging ground conditions.

The engineering design was informed by the available ground investigation data and detailed pile design analysis. CFA piles were designed to achieve maximum safe working loads of approximately 310 kN, providing reliable support for the residential structures.

Pile lengths were typically designed in the range of 10.0 m to 12.0 m, allowing loads to be transferred beyond the weaker near-surface clays into more competent strata at depth. The reinforced piled raft slab was designed to integrate seamlessly with the building structure, supporting both internal loadbearing elements and the outer skin of brickwork while maintaining structural efficiency and durability.

The selected piled raft solution enabled a streamlined construction methodology. CFA piling minimised noise and vibration compared with alternative driven systems, making it particularly suitable for the rural residential setting.

Once piling works were completed, the reinforced raft slab was constructed as part of the substructure works, creating a stable platform for the superstructure. The integration of piling and raft construction simplified site sequencing and supported efficient programme delivery.