Some of the larger hydropower dams in Sweden are buttress dams, consisting of up to 100 concrete monoliths formed by a front plate with a supporting buttress. Cracks have been observed in some dams, through the buttresses and at the base close to the rock foundation. The combined effects of restrained thermal displacements and loads caused by water are studied through finite element analysis. The results demonstrate the use of a non-linear material model and show that it is possible to follow the formation and propagation of the cracks. The analyses indicate that thermal stresses in combination with the loads caused by external water pressure are the reason for the cracking.