The strength, design flexibility and water resistance of concrete walls keep residential basements sturdy and dry. Although concrete walls are essentially maintenance-free, cracks are common and often inevitable. Fortunately, most cracks in basement walls are minor and generally elicit no structural damage to homes. There are several types of cracks, including vertical and horizontal, and each are caused by different sources. Knowing how to properly interpret cracks in a basement wall can give you insight on any structural problems that require attention.
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Inspect the basement walls for vertical or diagonal cracks. Vertical and diagonal cracks that emerge from the corners of windows or beam pockets are often caused by thermal contraction or concrete shrinkage. Erosion, poor drainage and vertical movement of the foundation can also cause vertical and diagonal cracks to start at the floor and spread up to the ceiling.
Analyze the walls for horizontal cracks. In many cases, horizontal cracks are indications of poorly constructed foundation walls. Horizontal cracks form when an applied load, such as backfill dirt, presses up against a wall’s exterior.
Examine the walls for stair-step cracks that emanate from a window or door. Stair-step cracks indicate vertical movement among two or more foundation sections. These cracks signify either a settling or heaving foundation and indicate that a foundation need stabilizing.
Search for any thin cracks in the walls. Hairline cracks are the most prevalent in basements and can appear only weeks after foundations are poured. The curing of a home’s foundation generally causes hairline cracks in a basement's walls.