Foundation Cracks occur because as the foundation is curing the concrete shrinks due to water loss.

Every Foundation Will Have Cracks

The typical places that cracks form are at:

How Can I Prevent Foundation Cracks From Leaking?

The best way to prevent foundation cracks from leaking is to have the foundation coated with a Waterproofing Material during construction. Damp Proofing is not Waterproofing and will crack with the foundation. Waterproofing is designed to be able to stretch over foundation cracks as they form. The Waterproofing will bridge over these cracks and prevent them from causing leaks.

How Do I Know If I Have A Crack In My Foundation?

If your basement is finished the only way to know for sure what the problem is would be to remove the drywall and insulation to expose the foundation. Alternately you may be able to dig out the outside of the structure to find the leak source (more difficult).

How Do I Know If A Crack Has Been Leaking?

Obviously if the crack is wet there is a leak, but if a leaky crack has dried up it will have a white or brown powdery substance called effervescence (salts and minerals). This is made up of mineral deposits and salts that are left behind as the water dries. This residue will be on the wall where the water has leaked in before.

I Still Can't Find The Source Of The Leak... How Do I Do A Water Test?

If your basement is finished make sure to at least pull the carpet back so you can visually see where water starts to build up.