The prolonged extreme drought in the Netherlands was reported to be increasing problems with house foundations, with nearly half a million homes said to be at risk. Foundation restoration companies were receiving more calls from residents who had found cracks in their walls after returning from holiday, and further damage was expected in the coming years. According to soil subsidence expert Otto Levelt of Deltares, homes with shallow foundations on clay soil could suffer damage because drought causes the clay to shrink and move beneath the foundations. This can lead to cracks in walls and doors or windows becoming stuck. Extreme weather associated with climate change can worsen the problems.