Cracks are not good for any object, nonetheless the foundations of your home. Just as you mention the word crack, you are immediately associated that something is broken and not good enough. In fact, the foundation is the core of the house. Thus, it should be as firm and strong as possible. Speaking of the crack in the foundation, there are many things that can cause them. Most importantly, as soon as you notice the crack, you should find what causes it and then fix it.
Causes for the Cracks in the Foundations
Finally, if you have a crack in your home, click the link below and read something more about the things that can cause it.