But during a building’s lifetime, arising from normal wear and tear and the expansion and contraction that takes place during winters and summers, small cracks will appear in the concrete. These cracks can allow water inside, water that can freeze, expanding and creating a deeper crack. This type of attrition and erosion is what all stone buildings have to put up with. It is also what mountains have to put up with, which is how they get eroded. To prevent stone or concrete structures being similarly afflicted, maintenance of their fabric needs to be carried out every fifty years or so.