Cracks in the foundation wall, cause, effect and solution

There are no perfect houses and that would include their foundations. Whether you have a new house or one that is a hundred years old, the foundations of houses crack. Houses change and settle after construction. Homes will have cracks in cosmetic finishes or structural components. Most of these cracks are of no structural significance. Common types of foundation wall cracks will include;

Vertical (or almost vertical) cracks; Just because a wall has cracked doesn’t mean it has failed or corrective action is required. If the crack is narrow (1/8 inch or less), is nearly vertical, has no lateral separation between adjacent parts of the wall, and no water seeps through the crack, then generally no action is required. This is a shrinkage crack and occurs when moisture in the wall evaporates, causing the wall to shrink into the voids created by escaping water. These types of cracks are controlled, or minimized, but not eliminated, by the use of horizontal reinforcing steel, which helps distribute stresses in the wall. If horizontal steel is present, you are more likely to have several very small cracks rather than one or two much wider cracks. Another method to limit shrinkage cracks is to control the amount of water used in the concrete mix.

reentrant cracks; Whenever a concrete element has an acute angle, there is a stress concentration. This almost always results in a crack called a reentrant crack emanating from the inside corner. It can be vertical, horizontal or diagonal when leaving the corner. This phenomenon exists in almost all materials. Round openings can dissipate stress, but this is impractical in concrete wall construction. The typical remedy to reduce this type of crack is the placement of steel reinforcement in the corners. It won’t eliminate these cracks, but it will keep them tight and in check.

Horizontal cracks; Horizontal cracks require more scrutiny. Most residential foundation walls are designed to span from the base or floor slab to the upper story framing connection. An 8-inch concrete wall in normal soil conditions is generally strong enough to withstand the forces exerted on the wall without vertical reinforcement. Exceptions include areas with high groundwater conditions or expansive soil conditions. If there is a vertical brace in the wall, a horizontal crack is probably not a concern. An expert should be consulted before the appearance of a horizontal crack to assess whether there is a structural risk.

These cracks usually result from one or more of the following;
1. Settling of the soil under the foundation results in downward movement of the foundation and displacement is common in most newly built homes.

2. Alteration of the local water table every time a new house is built. Specifically, the ground under the house dries up; the resulting soil contraction causes minor settlement of the footing, which can cause very little cracking in the foundation walls.

3. A new house, without furniture or effects, does not impose a significant load on the foundation. Once all of your furniture and appliances have moved, the weight supported by the foundation and overall structure increases, causing some flexing (or movement) of structural members throughout the building. This increased load can cause hairline cracks in the foundation.

4. Shrinkage by drying. As poured concrete dries and hardens, it will shrink. The main factor influencing drying shrinkage is the total water content of the concrete. As the water content in the poured concrete increases, the amount of shrinkage increases. Significant increases in sand content and significant reductions in the size of coarse aggregate used in poured concrete increase shrinkage because the total water content is increased and the smaller size coarse aggregate provides less internal resistance to shrinkage.

5. Thermal expansion and contraction of concrete. Concrete poured during high daytime temperatures will shrink as it cools overnight, which may be enough to cause cracking if the concrete is contained.

6. Restricts; The restriction of the free movement of fresh or hardened concrete after the completion of placement (concrete pouring) in the formwork or within a confined space; The constraint can be internal or external and can act in one or more directions.

7. Settlement or movement of the subgrade. The detachment of the soil or footing due to their mass, the loads imposed on them, or the contraction or displacement of the underlying support.

Most foundation cracks are minor and insignificant; are common to poured concrete and block foundations. Structural (horizontal) cracks in residential foundations are often the result of settlement and/or horizontal loading. They can be the result of hydrostatic pressure or the use of heavy equipment next to the foundation. The possible implication of foundation cracks is the penetration of moisture, moisture that can ruin wall coverings, floor coverings, and finished furniture.

Water will seep through a foundation crack if there is enough hydrostatic pressure to force water through the crack. If a waterproofing system was installed during construction, the basement may not leak even if there is a large crack. Keep in mind that waterproofing is not the same as waterproofing. Installing an exterior waterproofing system after the wall has been filled can be prohibitively expensive. The best solution is the use of an epoxy injection system. It will stick to the side of the cracks and can actually strengthen the wall. These systems can be DIY, but it is highly recommended that they be applied by a professional.

If you remove anything from this article… take this. All foundations crack, your foundation, my foundation, and most of these cracks are insignificant and have no structural implications. If you have any doubts about the size and type of crack, call a professional to evaluate it.