Cracks Appearing in an Outside Concrete Block Wall of a Basement

Patterns

• Cracks may be horizontal, vertical or stair-stepped. InspectAPedia notes that cracks in concrete block walls most frequently are horizontal. Horizontal cracks are considered more serious than vertical cracks and have the potential of resulting in collapse.

Shrinkage

• Mortar between blocks of concrete will shrink as it cures, according to InspectAPedia. This usually happens most toward the center of a wall and generally the cracks are a uniform width. Cracks caused by shrinkage are not a serious concern, except that they will provide access for water or radon to enter a home.

Joints

• Cracks that occur in mortar along joints might be caused by the pressure of water, frost, wet soil, the weight of vehicles being driven close to the wall or uneven footing settlement. These are the most common types of cracks in concrete block walls, according to InspectAPedia. Those found near the corners of the foundation usually are caused most often by frost and water.

Vertical Cracks

• Vertical cracks of the same width are indicative of uneven settlement that most likely involves the home's footings. A vertical crack wider at the top than the bottom might indicate that the footings have bent and settled unevenly. Vertical cracks also might be caused by impact to the wall, such as from heavy equipment used during construction.

Step Cracks

• Step cracks in a concrete block wall resemble a stairway. They are not a serious concern if the cracks are fine. However, open cracks indicate significant settling of the wall. It might be necessary to rebuild the entire wall.

Repair

• Cracks should be inspected and assessed by a professional to determine the extent of the problem. Minor cracks can be repaired using injections of epoxy and polyurethane-based materials, according to Cyberspace Marketing Corp. The National Association of Realtors recommends that individual blocks be repaired by removing and replacing the face of the block.