Rufisque soils have been for a longtime considered as formed from attapulgites that have no swelling capacity. Therefore, structural causes have been advanced to explain numerous building damages. The difference in the scales of the damage on the structures and the faulting of the substratum lead us to revisiting the question. A wide combination of investigation methods allowed revealing that Rufisque soils have actually expansive properties due to the possible neogenesis of montmorillonite from attapulgites. Moreover the presence of swelling clays must be combined to particular geomorphologic and hydrologic factors to imply significant damages.