Recent foundation and rock-excavation works have shown that the gneiss bedrock in the harbour area of Karlshamn is clay-weathered. Swelling clay minerals form part of the weathering products and this has created a number of practical problems, the choice of a suitable foundation pressure to avoid heaving being the most important one. This requires the prediction of a reasonably safe value of the swelling pressure and it is shown that the Yong & Warkentin theory can be used for this purpose, provided that the density of the clay mass is fairly moderate and that the particle orientation is taken into consideration. □ Engineering geology, foundations, settlement, rock excavation, clay-weathered gneiss, weathering, swelling clay, heaving, ground pressure, swelling pressure.