Most concrete foundations can and will crack over the years. Most small cracks are insignificant and nothing to worry about. However, if the crack starts to grow, and penetrate through your entire slab of concrete, it can make the foundation vulnerable to water leaks through the bottom. This could be particularly problematic foundations in basements. So, if you have exposed foundations in your basement or garage that are cracking, it could be very helpful if you seal them with crack filler.