Visually inspect your foundations at least annually. For concrete slabs, look for cracks, soil separation from the edges of the slab, water stains or discoloration, or evidence of pest intrusion (mud or mounds of dirt on the slab edges). In a climate with elastic soils, some cracking is not unusual. But large cracks (greater than ¼-inch) should be evaluated by an expert, especially if any buckling or warping of walls or floors is also present.