Types of Foundation Cracks and Their Causes

There are so many things that can occur to a home over time. Although homes are built to last, wear and tear can eventually occur. One of these issues is foundational cracks. Foundations hold up the weight of a home on the soil of the ground. This makes a foundation susceptible to different changes that can cause it to crack or fail. Many homeowners can benefit from knowing whether these cracks can develop into structural issues. This article will provide information surrounding the types of cracks that can occur in foundations and their causes.

Vertical Cracks

Vertical cracks are large cracks that typically appear when the foundation settles unevenly. These types of cracks are common in new construction. The settling of soil causes additional pressure to build up against the foundation walls, eventually leading to cracking. Vertical cracks can allow water to seep into the foundation, so these cracks should be repaired fairly quickly. Additionally, see the technical details regarding vertical cracks below:

• These cracks occur in the middle of foundation walls.
• Usually, vertical cracks are 1/8 – inch wide.
• If they are wider than ⅛ – inch, then it is a serious problem, and the homeowner should seek a professional to sort the issue.

Horizontal Cracks

Horizontal cracks typically indicate that heavy soil pressure is present on the foundation walls.  Horizontal cracks are more serious than vertical cracks because vertical cracks are a common result of a house settling. Horizontal cracks occur when the soil is overly saturated with water and pressure is being exerted against the foundation walls. These types of cracks can cause foundation walls to buckle, resulting in structural instability. Horizontal cracks are serious in nature. They usually are caused by flooding or heavy rains, which increase water pressure on the foundation. Urgent repair is required when they are discovered, or it can lead to serious damage to the home’s foundation.

Stair-Step Cracks

Stair-step cracks are often seen in retaining walls or block foundations due to excessive soil pressure or uneven settlement. The mortar joints of the blocks will tend to crack if this occurs. They are seen in a stair-step pattern throughout the walls and can indicate there is a foundational issue that needs to be addressed.

What are the Causes?

Most concrete finishes will crack over time because of the material mechanics of concrete. Concrete expands and shrinks due to temperature changes and moisture on their surfaces. One thing to note is that concrete cracks can occur during construction when a home is first built. It is hard to detect the cracking until the concrete has formed completely.

Concrete foundations will show cracks in weak points, especially where the foundation meets the walls. For example, cracks can occur at corners, the basement window frame, and pipes. Here, the list below will expand on the most common causes for concrete foundation cracks:

1. Moisture
   • Soil shrinks and behaves similar to a sponge when moisture is taken from it. When moisture is withdrawn from the soil below the concrete foundation, a gap is created. This gap then allows the foundation to alter its placement, which means the foundation can settle. The foundation now moves freely because it is unsupported due to that gap, so it can settle, causing the appearance of a crack. Similarly, when too much moisture gets into the soil, it causes the soil to expand.
2. Earthquakes
   • Earthquakes shake the ground, so once the foundation becomes unstable and unsupported, it can move and cause cracks. Some weaker earthquakes can expand existing cracks in the foundation.
3. Storms and flooding
   • Any type of storm that produces a substantial amount of drainage can damage the foundation of a home. When an overflow of drainage tries to push against a home and the soil is not prepped or capable of infiltration, the soil will begin to expand. That structure is now unstable, so it will shift and crack. There are preventative measures that can be taken to try and protect the structure during a storm event.
   • Many California homes do not have to deal with the freezing and thawing cycle that occurs during the winter months, but this is another cause of foundational cracks. Again, the mechanics of concrete contribute to this issue.
   • Flooding can be from a storm event or insufficient drainage infrastructure. Excessive flows of water can cause a buildup of hydrostatic pressure. This means the pressure exerted by the fluids builds over time and can cause a rupture in the foundation.
4. Plumbing Leaks
   • Leaks in the plumbing pipes can cause some flooding or hydrostatic pressure issues. Essentially, the excess water can cause the soil underneath the foundation to expand and push the foundation walls. Basements should be waterproofed or have a sump pump to provide potential mitigation.
5. Heat
   • Concrete does have the potential to crack under extreme heat. Heat causes concrete to expand, so once the concrete shrinks after the heat source is removed, the foundation could have shifted or changed its position.
6. Construction Defects
   • Poor reinforcement and weak-graded concrete can cause undersized footings and create construction defects. This type of scenario will make the foundation walls more prone to cracks.
7. Soil Pressure and Settlement
   • Soil underneath a foundation wall can compress or even be misplaced in a flooding situation. This will cause the foundation wall to crack vertically and settle.
   • Expansive soils such as clay, when saturated, can push against a foundation wall with significant force. If that pressure is substantial, the wall can develop horizontal or diagonal cracks. The walls can become displaced and start to tilt when this occurs.

Fixing the Cracks

There are methods available to fix cracks. Waterproofing the basement foundation walls and epoxy injections can mitigate foundation cracks. Also, concrete foundations can crack in construction, so making sure a good contractor is hired may avoid this issue. 

After looking into the types of cracks and what causes them, it is imperative to ensure the foundation is always stable and well supported. If the foundation can potentially be shifted by expanding soils or the dry soil is not packed in next to your home’s foundation, it may be time to hire a professional to look into the problem. Design Everest has a team of professionals with expertise in waterproofing the basement and epoxy injections to mitigate foundation cracks. Also, if no existing cracks are visible, Design Everest can look into preventative practices to avoid the potential of foundational cracks. Call us today to get started with a free quote and consultation.