Latimer Road Apartment Block, Wokingham

The site ground conditions comprised Made Ground over the Bagshot Formation and London Clay. Ground investigation also identified ground gas and sulphate conditions within the Made Ground. These results were considered as part of the concrete specification, resulting in a DC-2 classification for both the raft and piles.

The proximity of the railway was an equally important consideration. The building could not simply be designed with a standard pile arrangement across the entire footprint. Pile lengths and capacities needed to be carefully controlled in the areas closest to the railway.

The live railway immediately alongside the site was one of the main challenges for the foundation design. Network Rail’s Track Support Zone placed restrictions on the piling works, meaning the pile design had to change across the building footprint.

Rather than using the same pile capacity everywhere, SPEEDECK developed a zoned piling design. Piles closest to the railway were shorter and designed for lower working loads, with pile lengths and capacities increasing further away from the railway boundary.

Pile lengths across the development typically ranged from 9m to 18m, with the maximum safe working load reaching approximately 610kN in the areas furthest from the railway. This approach allowed the foundation design to work with the site’s constraints while still providing the support required for the apartment building.

SPEEDECK designed a single 1,155m² piled raft foundation, constructed at 300mm thick and incorporating two lift pits and movement joints to suit the building layout. A key advantage of the SPEEDECK system was the ability to work from a concrete working surface rather than requiring a traditional granular piling mat across the entire site.

A lightweight piling rig was used to construct the piles from the uprated concrete blinding layer. This helped reduce the need for additional excavation, imported aggregate and muck-away across most of the footprint. However, because the site was immediately adjacent to a live railway, the area within the railway’s zone of influence required a granular piling platform to meet the relevant Network Rail requirements.

The solution therefore combined the benefits of our concrete working surface with the additional requirements imposed by the railway. The foundation was designed specifically around the building, the ground conditions and the restrictions created by the railway. The ground investigation identified no significant heave risk beneath the footprint, meaning that void formers were not required beneath the piled raft. The concrete specification was also developed to account for the DC-2 classification identified through the ground investigation, applying the appropriate requirements to both the raft and pile concrete.

By bringing the structural and foundation design together with the construction methodology, SPEEDECK was able to develop a practical solution that could be built within the constraints of the site.

SPEEDECK delivered the piling and raft slab as a single coordinated substructure package over an 8-week programme.

Across most of the site, the piles could be installed from the concrete working surface rather than a conventional piling mat. This simplified the construction sequence and reduced the amount of additional material required across the footprint. Within the railway’s zone of influence, a granular piling platform was retained to meet the necessary requirements.

Once completed, SPEEDECK handed back the finished plots ready for the following construction trades, allowing the apartment building’s superstructure works to progress.