A developer rang us last month from a site off Eastern Avenue. They had stripped the topsoil and hit a mixed layer of Lias clay and river terrace gravel within 900 mm. The structural engineer needed a 150 kPa bearing pressure for a two-storey extension. Without a site-specific shallow foundation design, the building control submission would have stalled. Gloucester sits on a complicated transition between the Severn Vale alluvium and the Jurassic limestone outcrops that run toward Robinswood Hill. That means presumptive bearing values from a desk study are rarely enough. We run the investigation, log the strata, sample the cohesive layers, and produce a foundation design package that matches the actual ground, not a generic assumption. For sensitive schemes near the Gloucester Docks, where historic fill masks the natural profile, we often tie the investigation into a wider ground investigation programme to map the buried services and old dock structures before setting the formation level.
A foundation designed on presumptive values in Gloucester clay costs more to remediate than the investigation needed to get it right the first time.
