Foundation floor cracks occur most often as the concrete cures on the basement floor. Combined with the natural expansion and contraction of concrete with moisture and temperature, they are usually not a warning sign of a foundation problem and are not cause for alarm.
However, foundation floor cracks, when combined with poor drainage, can lead to groundwater leaks into the home. As groundwater rises, they find their way into your home through these cracks, enter the home, and flood the basement.
Fixing these cracks, however, is a simple process if you have a perimeter drain installed. Perforated pipe can be installed under the floor, with a line running from the pipe to either the perimeter drain or the sump pump. This installation is very fast, and combined with the installation of a perimeter drain and sump pump should take less than two days.
If the foundation floor cracks are not leaking, you may still wish to seal them for aesthetic reasons, to keep the floor looking uniform, and to help prevent radon gas from seeping in (although sealing floor cracks is no substitute for a radon mitigation system). Sealing these cracks with a urethane or polyurethane patch is a convenient, easy way to handle this. The job is very easy and inexpensive, and should be a painless repair.