What Are Foundation Cracks: Causes, Types, and Repair (2024)

By Amanda Lutz Updated May 13, 2024

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Discovering structural issues in a home can be scary. But if you’ve noticed some cracks in your crawl space, basement walls, or concrete foundation, you don’t necessarily need to contact a foundation repair company. Some small cracks around a home are completely normal and safe, while some need to be addressed by a structural engineer to prevent further damage.

Below, we explain different types of foundation issues, what they mean, and when it’s time to call a pro.

What Causes Foundation Cracks?

Even a well-designed, solid foundation can develop problems. Here are the main culprits.


The leading cause of foundation cracks is poor drainage around a home’s foundation. Too much rainwater causes a buildup of hydrostatic pressure against concrete foundation walls and leads to structural integrity issues. This can sometimes be remedied via waterproofing, whether it’s installing gutters with extended downspouts, fixing grading issues, or applying protective membranes around the home’s foundation.

Other moisture-related foundation damage can stem from traumatic weather events, such as frost heaves, floods, or frequent bouts of extended rain. Even if you have the perfect drainage system, a home can simply receive too much wear and tear from Mother Nature, leading to wall cracks or a cracked foundation.

Poor Materials

Substandard materials could be the root cause of structural damage. For example, if faulty cinder blocks were used or the concrete poured to make your basement floor wasn’t mixed and cured properly, you may see structural problems over time.

Homes with foundation problems caused by shoddy construction materials sometimes need extensive work, but that’s not always the case.

Soil Conditions

Three types of soil issues may contribute to cracking foundations:

  1. Expansive soil: If the house was built atop soil with lots of clay, the earth beneath and around your foundation changes every time weather shifts. Heavy rainfall causes the clay to expand, while periods of drought cause it to shrink.
  2. Soil creep: Homes that aren’t properly graded can have erosion issues over time. Heavy rainfall causes soil to drift downhill, which creates soil pressure against the home. If this happens, improving landscaping via a professional grading company is crucial.
  3. Uncompacted soil during construction: Construction companies hasty to begin a building project may not have properly packed down the soil before laying the foundation. This can lead to differential settlement, which is when one part of the house settles at a different angle and rate than the rest of the house, causing serious structural damage.

Types of Cracks in Foundations

There are five types of foundation cracks you should know about.

Diagonal Cracks

Diagonal foundation cracks are likely the result of foundation settlement. They often occur in homes with concrete foundations and do not suggest a serious structural problem. Homeowners can fix diagonal cracks with a simple DIY epoxy injection.

Hairline Cracks

Hairline cracks are common in new homes as they settle and can be found in concrete slabs or drywall. Shrinkage cracks can usually be fixed with a masonry crack filler, which you can purchase via Amazon for around $15.

Horizontal Cracks

Horizontal cracks in a home’s foundation can be caused by shifting soil or too much water pressure on the foundation. These structural problems need to be professionally addressed as soon as possible. Repair companies will often use a carbon fiber wall strap to repair the horizontal crack. This material is extremely strong and can even stop bowing in the walls. Repair costs vary and typically depend on the horizontal crack’s size.

Stair Step Cracks

Concrete block foundations are prone to stair-step cracks (thus named because the cracks resemble steps going up the concrete blocks). While stair-step cracks can be caused by a few different things, they’re commonly due to moisture or settlement sinking.

Unfortunately, stair-step cracks generally require a foundation repair expert, but if the crack only appears on the mortar joints, it may only require a reapplication of mortar. If the blocks themselves appear displaced or damaged, more extensive repair may be needed.

Vertical Cracks

Vertical foundation cracks are most likely not a problem. They sometimes occur when concrete cures or the foundation settles, but they can often be fixed with DIY repair methods. Common fixes include applying polyurethane or epoxy injections.

Structural vs. Nonstructural Foundation Cracks

A structural foundation crack is one that will pose structural problems if left unremedied. They require more than caulk and paint to remedy. According to the National Association of Homebuilders (NAHB), if the cracks are horizontal or larger than 3/16 inches, you need to call a professional. Contractors will likely need to reinforce the foundation to remedy and prevent future damage.

A nonstructural foundation crack does not represent an immediate threat to a home’s structural integrity but is still a bit of a nuisance. Homeowners with these types of foundation cracks may notice leaking during rainstorms or snow melts. Because water can wreak havoc on a home, nonstructural cracks should be treated quickly to prevent mold or water damage.

When Should I Be Worried About Foundation Cracks?

Homeowners should be worried about horizontal foundation cracks. This is a sign the interior walls are bowing under intense pressure. As mentioned, this can be caused by soil displacement or hydrostatic pressure. Not only will the home need work, but it may need landscaping.

How to Repair Foundation Cracks

Crack repair can be a feasible DIY project. Many homeowners feel competent to handle epoxy injections or use a masonry repair kit.

More extensive cracks should be left to professionals who will likely use a pier, such as a helical pier. Helical piers look like giant corkscrews and are installed directly underneath the perimeter to push the foundation up and keep it level. Multiple piers are often needed, and each pier comes with its own installation cost.

Our Recommendation

Foundation cracks should not be ignored because they may indicate structural problems that lead to long-term damage. Most foundation cracks are fixable, but they may not be cheap. If piers are needed, the cost can increase significantly. Plus, homes that require piers generally need more than one. Structural foundation cracks should be left to a professional foundation repair company.

To prevent cracks moving forward, homeowners should take the following steps:

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Foundation Cracks FAQ

What size of foundation crack is a concern?

According to the NAHB, foundation cracks that exceed 3/16 inches should be addressed. This holds true for both horizontal and vertical cracks.

Is it OK to have cracks in the foundation?

It’s normal to have some cracks in your foundation. Hairline cracks often occur when concrete dries and hardens, but repair is needed if the crack is significant in size.

What can I do about foundation cracks?

Foundation cracks can be addressed with DIY remedies or calling a professional. Foundation crack repair sometimes requires helical piers, slab piers, drilled concrete piers, and underpinning with piers. Homeowners should consider contacting a professional foundation repair contractor if the problem is not easily remedied.