A common mistake we see in Slough is assuming the stiff orange-brown clay at the surface will stay that way. Developers dig a trial pit, see dry material, and proceed with a standard strip footing. Six months later, cracks appear. The culprit is almost always the desiccated crust of the London Clay formation reacting to seasonal water content changes, something a basic site walkover simply misses. Our shallow foundation design process avoids this by combining precise in-situ testing with laboratory classification to model long-term volume change potential. For projects near the Jubilee River or older brickearth deposits, we often recommend supplementing the investigation with a plate load test to verify the modulus of subgrade reaction before finalising the bearing pressure.
Designing for London Clay in Slough means managing a high plasticity material that can heave or shrink by over 40mm seasonally.
