A recent three-storey apartment development off the Station Road ran into trouble within the first two metres of excavation. The grey-brown boulder clay that defines so much of Newbridge’s subgrade was wetter than any desk study had predicted, and the standard strip footing solution collapsed into a logistical and geotechnical headache. We were called in to redesign the foundation system, and the answer was a rigid raft that spanned the soft lenses without over-excavation. In Newbridge, where the glacial till transitions sharply between stiff matrix and pockets of laminated silt, a raft/mat foundation is rarely just an option—it becomes the most rational engineering path when bearing pressures drop below 100 kPa. The design process couples structural load distribution with a detailed ground model, often informed by CPT testing to map the vertical variability that boreholes alone can miss. With IS EN 1997-1:2005 as the governing code, every raft we design for Newbridge projects is checked for both ultimate limit state punching and serviceability settlements under the characteristic combination of loads.
On Kildare boulder clay, a rigid raft routinely cuts differential settlement to under 15 mm—well within the IS EN 1997-1 serviceability envelope.
