We see it regularly on Ashford sites: a contractor opens a cut for a basement on a residential plot near Kennington, assumes the ground will stand up for a few days, and by Tuesday morning there is a slump in the face and a call to the building control officer. The Weald Clay underlying much of the borough looks competent in the dry but weathers rapidly once exposed, losing suction and collapsing without warning. A retaining wall design done before the shovel hits the ground changes that scenario completely. Rather than reacting to instability, the job moves forward with a shape and reinforcement schedule that accounts for the actual soil pressures and groundwater perched in the sandy lenses that dot the Ashford area. Pairing the design with an in-situ permeability test lets us quantify how fast water moves through those lenses, which directly drives the drainage specification behind the wall.
A retaining wall in Ashford lives or dies by the drainage detail behind it — get that wrong and even a heavily reinforced stem will tilt within two wet seasons.
