ALL CONCRETE CRACKS. Concrete, masonry and mortar may develop hairline cracks or may develop spalling due to shrinkage, expansion and contraction. As it cures, concrete shrinks at a rate of about ¾” in every 100’. So this means that for a basement floor that is 70’ wide, the slab will shrink about 5/8”. This shrinkage will be visible as cracks in the slab. We hope and intend that the cracks occur in and are hidden by the control joints we provide according to the ACI (American Concrete Institute) guidelines. But since concrete is a natural product, it does not always crack at the intended control joint locations. These cracks or spalling do not affect the structural integrity of the building, are impossible to eliminate, are considered normal and are not warranted. Contact us if any of the cracks exceed the tolerances listed in the BIA Homeowners Manual or if cracks in the foundation wall begin to leak.