Are My Home’s Foundation Cracks Structural or Non-Structural?

If you live in the clay soil regions of Texas, it’s understandable that cracks in your foundation would be upsetting. Actually, cracks in your foundation regardless of your locality can be a serious matter. The expansive clay soil in Texas is especially destructive to foundations and it’s important that any crack you notice be given careful attention.

Cracks are broadly categorized into two types: structural and non-structural. Simply stated, structural cracks are visible structural damage to your foundation. A foundation that’s structurally damaged means its ability to support the rest of your home is compromised. Over time this damage can worsen to the point where the foundation is no longer flat and level but becomes uneven. The floors, walls, and ceilings of your home are likewise uneven, distorted, and cracked.

By contrast, non-structural cracks have no effect on the structural integrity of your foundation. Although some of these cracks are unsightly, they are otherwise structurally harmless. This doesn’t mean they can’t cause other types of problems. Depending on their size and your circumstances they may cause water seepage and insect infestations.

Causes and Appearance of Non-Structural Cracks

Non-structural cracks are most often caused by internally induced stress within the concrete. An example of this is shrinkage cracks. As concrete cures and hardens, it loses water and shrinks. During this shrinkage, the concrete steadily gets more rigid which in turn resists the shrinkage. At some point the concrete’s rigidity resists any further shrinkage. By this time however, a great deal of built-up internal stress causes the concrete to develop small cracks. These are usually hairline or less than 1/8 inch in width and tend to wander about. Sometimes they will stop at one spot and then start up again a short distance away. They often radiate out from the corners of rectangular holes in the concrete and from embedded objects such as pipes and drains. Weathering will also cause non-structural cracks on the concrete’s surface.

Causes of Structural Cracks

Structural cracks have a number of causes including poor construction, design mistakes, overloading, and soil movement. In expansive clay soil regions, the primary cause of foundation problems is soil movement. Expansive clay soil is affected by moisture in much the same way as a sponge. It expands when it absorbs moisture and shrinks when it dries out.

If it has been raining very hard where you live and the area around your home has poor drainage, your foundation can be damaged from the heaving effects of the soil as it expands. During a prolonged drought, damage occurs from soil shrinking away from your foundation. It’s the uneven movement of the soil that stresses and cracks your foundation.

Appearance of Structural Cracks

Structural cracks tend to be wider than 1/8 inch. The edges of the crack are either off-set or flush. Sometimes they are wider at one end than the other. One common pattern is the stair-step crack. This occurs in foundation walls made from concrete blocks and mortar. Because the mortar is weaker than the blocks, the crack follows the mortar in a diagonal stair case pattern.

In poured concrete, the cracks can be vertical, horizontal, and diagonal. They also occur in patterns such as diagonal cracks starting at the four corners of a wall and intersecting at a horizontal crack. If a horizontal crack is low on the wall near or below ground level such as inside a crawl space, it’s a sign that external soil pressure is causing the wall to buckle inward. If this buckling process continues, the wall eventually collapses.

If you see structural foundation cracks like the ones described above, the rest of your house is probably affected. Examples of this include uneven floors, sticking doors and windows, cracks on interior and exterior walls, and cracks between sections of your house such as between your chimney and the wall.

If you see evidence of structural cracks, get it resolved quickly because the damage gets progressively worse with time. If you have any questions or concerns about your foundation, contact us at Perma-Pier Foundation Repair.


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