It is not uncommon to have a crack in your foundation; even new homes can have foundation cracks. Typically foundation cracks under 1/16 of an inch do not have a significant impact on the performance of the foundation. However, cracks 1/8 of an inch or larger may weaken the slab. Larger foundation cracks can be repaired by injecting structural epoxy. The bonding strength of some epoxies can actually be stronger than the concrete.