Diagonal Crack From the Window in a Concrete Basement Wall

About Concrete

• Concrete is a mixture of Portland cement, aggregate and water. Though the terms “concrete” and “cement” are often used interchangeably, they are different materials. Cement acts as a binder with aggregate and water to create concrete. Because concrete contains a great deal of water by its nature, it is subject to expansion and contraction that occurs when temperatures fluctuate. Water crystals freeze and thaw, creating pressure within the concrete. Settling of the soil beneath the concrete can also cause shifting of structures and cracking at the weak points. Proper concrete installation can prevent many of these problems.

Concrete Basement Wall Cracks

• Concrete basement wall cracks are common in homes. The type of crack often indicates what force is creating the problem, according to the Concrete Foundations Association of America website. Temperature and shrinkage often manifest as vertical or diagonal cracks. These cracks often begin around a window, beam packet or other opening. Horizontal cracks are most likely to be caused by load problems. Cracks in concrete walls often widen over time, creating an unsightly appearance that decreases the value of your home.

When to Be Concerned About Cracks in Basement Walls

• Because small cracks in concrete are common in nearly all concrete structures, they are generally not a cause for concern. When cracks become larger than ¼ inch in width, however, they can become a source of leaks and should be inspected by a concrete contractor to determine whether any serious structural problems threaten the building. Long horizontal cracks, for instance, can be a sign of shifting and load-bearing pressures that can eventually collapse the wall.

Repairing Basement Wall Cracks

• A number of methods are available to homeowners to repair concrete cracks, such as small diagonal cracks around windows. Narrow cracks can be repaired with concrete patching compounds that are available at home improvement and hardware stores. These compounds may be a dry material that must be mixed with water or a premixed product that is ready to use.

  Repair is generally done by cleaning the crack and removing all loose material. The homeowner must then line the crack with a “glue” made of a thin mixture of the patch compound. This glue-like layer helps to hold the unthinned patch compound to the crack. Press the patching compound into the crack and level it to a smooth surface. Allow it to dry completely. Low-pressure injection with epoxy or polyurea materials is often used for larger cracks, according to the Concrete Network website.