Common-Wall Slab Cracks - Common-wall slab cracks are generally aligned parallel to the common wall of the house, usually 2” to 15” from the wall. Often, the crack flares away from the wall at an angle near the garage door opening. The common-wall slab cracks occur due to construction practices and the way the concrete dries or hardens. The crack usually occurs because of the way the foundation concrete was installed. A common-wall slab crack does not necessarily mean the foundation is structurally compromised either. Although the crack is unsightly and sometimes alarming, there is nothing a homeowner can do to manage this crack other than to put sealant (caulk) in the crack. As a matter of reference to the common-wall slab crack, review the garage walls and ceilings for interior cracks. In conclusion, spider cracks and common-wall slab cracks in the garage slab do NOT automatically mean there is a structural condition in the foundation. Often, these types of slab cracks are only cosmetic in nature and not structural related. If one observes wall cracks, corner cracks, and/or ceiling cracks in the vicinity of the common-wall slab crack, further investigation by a licensed engineer experienced in house construction may be warranted to investigate possible structural problems.