The laser level and total station are the first tools on site for a raft foundation in Luton, but the real work starts with the drilling rig. We mobilise a tracked window sampler rig across the tight urban plots and former brickworks of Bedfordshire to extract continuous disturbed and undisturbed samples. The chalk bedrock under Luton is notoriously variable—the Upper Chalk can be intensely fractured within the top few metres, while the overlying clay-with-flints can shift moisture content sharply between summer and winter. We combine the field data with a CPT test to read the cone resistance and sleeve friction in real time, which tells us where the soft lenses sit before a single cubic metre of concrete is poured. This physical evidence feeds directly into the bearing capacity and settlement analysis required under BS EN 1997-1:2004, ensuring the raft geometry matches the ground, not just architectural loads.
In Luton, a raft designed without accounting for chalk dissolution features can cost three times the original foundation budget in remedial grouting.
