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Why Is There a Crack in the Basement Wall?

Why Is There a Crack in the Basement Wall?

Basement cracks are often the result of an underlying structural issue, a leak, or both. Not all cracks are structural, however, and the crack that is giving you sleepless nights may be merely cosmetic.

The severity of a basement crack depends on several factors, including the crack’s size, location, direction, and shape. The time it took for the crack to form can also be an indication of its seriousness.

In this article, we will be taking a look at the different types of basement cracks as well as the various causes of each type of crack. Keep reading to learn more.

Types of Cracks

Shrinkage Cracks

A shrinkage crack is a thin, meandering crack that runs along the surface of a basement wall. It is typically shallow, and it is one of the most common types of basement wall cracks (especially with poured-in-place concrete walls). If you notice shrinkage cracks in your basement wall, the good news is that they are usually more cosmetic than structural.

Vertical Cracks

Homeowners with poured basement walls may sometimes encounter vertical cracks. These cracks are normally wider at the top than at the bottom.

If left unfixed, a vertical crack’s length and width will increase, leading to a crack that is ¼” wide or more.

Vertical cracks typically form after construction projects, and they can extend below the floor. In some cases, a vertical crack can result in water infiltration and moisture damage.

The only vertical cracks that are not considered to be structural are shrinkage cracks and cold joints.

Horizontal Cracks

When horizontal wall cracks start forming, it is usually in concrete block construction. The location of these cracks determines their severity.  This type of crack is widely considered to be the most severe and costly to repair.

Usually, horizontal cracks are near the ground, and their width and length depend on the cause of the crack. If you notice a horizontal wall crack, schedule a professional assessment as soon as possible to prevent further damage (and higher repair costs).

Diagonal or Stair-Stepped Cracks

Diagonal cracks typically run from the top of the basement wall down to the floor. In some cases, the wall can tilt inwards above the crack. Stair-stepped cracks are also diagonal cracks, but they typically occur in concrete block basement walls.

Like horizontal cracks, diagonal cracks may also require immediate attention to prevent further damage.

Causes of Cracks

Each type of basement wall crack has its own range of possible causes. Nonetheless, generally speaking, basement wall cracks are usually the result of:

  • Foundation movements as the result of soil issues,
  • Lateral pressures against the basement wall
  • The shrinkage process of concrete
  • Hydrostatic pressures

Shrinkage Cracks

When concrete is mixed, extra water is often used to hydrate the mixture. When this water evaporates, the concrete shrinks and shrinkage cracks start to form. To prevent shrinkage cracks, the concrete has to be poured at low temperatures.

Another way to prevent shrinkage cracks is to use more water throughout the concrete mixing process.

Vertical Cracks

Vertical cracks are typically the result of a cracked footing and differential settling. If the bottom of the vertical crack is thinner than the top, it is usually because a footing cracked and the one side shifted downward.

If the vertical crack is close to a corner, there may be two reasons for the crack. The first is that a segment of the basement wall is carrying more pressure than it is built to withstand. Thus, the perpendicular walls at the corner have to provide additional support to the edge.

The second reason for vertical cracks near a corner is if the roof gutters dump water on the soil just outside the house (near the corner), causing excessive water build-up. When this water freezes, it can cause vertical cracking in the basement wall. Changing the gutter system to drain the water elsewhere can prevent this problem from happening again.

Horizontal Cracks

Horizontal cracks are often the result of contractors who backfilled the exterior space between the basement wall and the edge of the hole that was dug (for the basement) before the wall was strong enough to withstand the lateral pressure of the soil.

A new basement wall takes around a month before it is strong enough to withstand the weight of backfilled soil.

Another common cause of horizontal cracks is when there is downward pressure on the soil next to the basement wall, which, in turn, adds to the lateral force on the basement wall. Vehicles and equipment can cause additional downward pressure.

If the horizontal cracks are in the top third of the basement wall, loading pressure on the soil at the top area of the wall is usually the cause.

If the soil next to the wall is heavily laden with water, it can also cause horizontal cracks. Addressing high water tables and poor drainage will usually prevent this problem from recurring.

Diagonal Cracks

The causes of diagonal cracks include lateral pressure against the top and mid-sections of the basement wall, shifting or expansive soil, and footing compaction issues. A diagonal crack can also be the result of a damaged first-floor sill plate.

If the exterior space between the basement wall and the hole was backfilled before the first floor of the house was framed, it can also cause diagonal cracks to form in the basement wall.

Contact Us

Basement wall cracks can form over a long time. In most cases, vertical, horizontal, and diagonal cracks are the result of things like foundation damage and backfilling issues. If you don’t address these problems, they can eventually affect the structural integrity of your house.

MTdrains is a plumbing and waterproofing company that services the entire Greater Toronto Area. If you notice a crack in your basement wall, we can provide you with professional foundation (and wall crack) repairs.

We will come to your home, assess the problem, and provide you with a free, no-obligation quote to address the initial cause and repair the damage. Contact us today to restore your home and save on future repair costs.



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