What Causes Foundation Cracks?

Whether you have a foundation made of concrete block, brick, or poured concrete, cracks can be alarming. Your first initial thought may be if the crack is superficial or disastrous. Below, we will go over what causes foundation cracks and the different types. 

Top Causes of Foundation Cracks


When there isn’t enough moisture, soil can shrink. When this happens it pulls away from the foundation and creates a gap. When the foundation is not supported properly it can shift and cracks will appear. 

• Storms, Flooding, and Plumbing Leaks

Inverse to the drought, too much moisture can cause the soil to soak up water and expand. This forces soil around the foundation to push against the foundation, causing cracks and bowing walls. 

• Freezing

When the temperature changes between freezing and thawing, concrete expands and contracts. 

• Extreme Heat

Under extreme sun and heat the concrete can expand, and then overnight as it cools the concrete will shrink and retreat back to its original position. 

• Earthquakes

It is obvious when the ground moves, your foundation will shift and crack. Thankfully large earthquakes are not extremely common, however even small earthquakes can create cracks and threaten your home’s stability. 

Types of Foundation Cracks

• Vertical Foundation Cracks

Vertical foundation cracks tend to be common in many homes, and often non-threatening. As seen above, they can be caused by shrinking of the concrete when the foundation was built. Most times these cracks are common and there is no reason for concern. Keep an eye on the crack to make sure there is no water leaking. 

• Horizontal Cracks

Beware of horizontal foundation cracks. These cracks often occur when the water and ground force presses against the exterior of the basement walls causing it to bow. These can indicate a serious structural problem. 

• Stair-Step Cracks

Beware of stair-step cracks. Similar to horizontal cracks, stair-step cracks occur due to pressure exerted on the wall pushing it inward. Concrete block foundation wall cracks respond by cracking along mortar joints between blocks. These cracks may be indicating that your wall is pulling apart from itself in all four directions and requires stabilization.

• Basement Floor Cracks

Most floor cracks are benign and occur shortly after the concrete floor is poured and shrinks as it cures. These are usually hairline cracks that never change over time. The two concerns for basement floor cracks are heaving and sinking. Signs of this are uneven cracks where the floor on one side is higher than the other. Keep an eye on these cracks to make sure they are not widening and no water is seeping through. 

Is My Foundation Crack an Issue?

Foundation cracks can grow and worsen over time which will compound your problems. If left unattended, foundation cracks can create a wet basement. Beyond the potential for a flooded basement, once moisture enters your basement it creates a perfect condition for mold to grow.

If you’d like a professional evaluation of your foundation cracks contact ‘58 Foundations & Waterproofing for a free foundation repair estimate.