How to Fix Stair-Step Cracks in Foundation: 5 Methods

August 18, 2023

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how to fix stair-step cracks in foundation

Stair-step cracks in concrete foundations are common and can lead to further structural damage if left unaddressed. These diagonal cracks that resemble a staircase often indicate that one section of the foundation has settled more than the rest. 

So, how to fix stair-step cracks in foundation? Stair-step cracks in concrete foundations can be repaired by injecting epoxy resin or polyurethane foam into the fissures to bond the concrete back together. For more severe cracking caused by ongoing foundation settlement, mudjacking, installing supports, or full foundation replacement may be necessary.

Thankfully, there are several effective methods for repairing stair-step cracks and preventing continued foundation movement. In this article, we will look at what causes these cracks and outline five ways to fix them, from epoxy injection to concrete foundation repair.

What Are Stair-Step Cracks?

Stair-step cracks, also called stair-stepping or stepped cracks, are diagonal cracks in concrete foundations that look like a flight of stairs. They occur when one section of the foundation settles more than the adjoining section, causing the concrete to bend and crack. Stair-step cracks are most common in slab foundations and basement walls.

Stair-step cracks are concerning because they indicate differential foundation settlement. If not addressed, they can lead to further cracking and structural damage. The good news is that there are several methods to repair stair-step cracks and prevent continued foundation movement.

stair step foundation crack

How to Fix Stair-Step Cracks in Foundation in 5 Ways

1. Epoxy Injection

Epoxy injection is the most common and effective way to repair stair-step cracks. This method injects an epoxy resin deep into the cracks under pressure. The epoxy bonds to the concrete and essentially glues the cracks back together.

Here is the epoxy injection process:

  • Clean out the cracks thoroughly and seal the surface with caulk.
  • Drill holes along the length of the cracks and insert injection ports.
  • Inject low-viscosity epoxy through the ports until it fills the cracks.
  • Allow the epoxy to cure fully (usually 24-48 hours).
  • Cut off the surface caulk and injection ports. Grind the surface smooth.

Epoxy injection provides a permanent structural repair and prevents water intrusion and further cracking. It can repair cracks up to 1⁄4 inch wide.

2. Polyurethane Foam Injection

Polyurethane foam injection works similarly to epoxy injection but uses expanding foam to fill the cracks. It has some advantages over epoxy:

  • Foam molds better to the uneven shape inside cracks.
  • It creates a waterproof seal.
  • It can repair moving cracks.

The process is the same as for epoxy injection. Clean and seal the cracks, drill entry points, and inject polyurethane foam until it fills them. The foam expands to fill the space completely.

Polyurethane works best for hairline and small cracks. For large cracks, use epoxy.

3. Route and Seal Crack

For shallow stair-step cracks less than 1⁄4 inch deep, you can route and seal the crack instead of doing an injection.

Here is the process:

  • Use a concrete saw or angle grinder to cut a u-shaped channel along the crack. Go at least 1⁄2 inch deep.
  • Clean out the crack channel thoroughly.
  • Fill the channel with a concrete patch or flexible polyurethane sealant.

Routing provides a decorative repair and seals the crack from water. It stops crack growth but doesn't structurally bond the concrete like injection methods.

4. Carbon Fiber Reinforcement

For very large stair-step cracks, carbon fiber reinforcement provides structural strengthening. You apply carbon fiber fabric over the cracks with epoxy resin. The carbon fiber bonds to the concrete while remaining flexible. This bridges the cracks while adding strength.

The process involves:

  • Grinding the surface for the carbon fiber fabric to bond.
  • Applying epoxy resin.
  • Laying the fabric over the cracks.
  • Coating with more epoxy resin.

Carbon fiber is best for cracks wider than 1⁄4 inch where significant foundation movement has occurred. Use in conjunction with epoxy injection for the best results.

5. Foundation Repair

In cases of ongoing foundation settlement, you may need foundation repair methods in addition to crack repair. Options include:

  • Mudjacking - Pumping concrete grout under settled areas to lift them.
  • Pier and beam - Installing supports to stabilize settled foundation sections.
  • Foundation replacement - Removing and pouring new foundation walls or slabs.

Foundation repair aims to prevent continued differential settling that causes stair-step cracks. Diagnose and address the underlying cause of settling first.

repairing stair step foundation cracks

When to Call a Professional

While DIY repairs are possible for minor stair-step cracks, it's best to have professional foundation contractors handle large cracks or signs of ongoing settling. They have the specialized equipment and skills for effective long-term repair.

Professionals can also determine if the root cause of cracking needs correction, like grading issues or water damage. Addressing underlying problems is key to preventing cracks from recurring.

Fixing stair-step cracks in your foundation as soon as they appear is important for structural stability. These cracks can be repaired with the right methods and prevent future foundation damage. Talk to foundation repair experts near you to discuss the best solutions for your home.

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Stair-step cracks in your foundation should be addressed immediately to prevent further structural damage. While minor cracks can be repaired with DIY methods like routing and sealing, it's best to have professionals handle large cracks or signs of continued foundation movement. They can diagnose the root cause and ensure effective long-term repairs are made. Keeping an eye out for stair-step cracks and fixing them promptly will help maintain the integrity of your home's foundation.

About Lexington Foundation Repair Experts

Lexington Foundation Repair Experts specialize in fixing all types of foundation problems, including stair-step cracks. With over 20 years of experience, their experts can diagnose the cause of your foundation issues and recommend the right repair solutions. The company uses advanced techniques like epoxy injection, carbon fiber reinforcement, and mudjacking to permanently repair cracks and stabilize foundations. To learn more about your foundation repair options or schedule a free inspection, call Lexington Foundation Repair Experts today at (859) 955-1990.


How serious are stair step cracks?

Stair step cracks in concrete foundations should be taken very seriously as they indicate differential settlement of the foundation. These cracks can worsen if left unchecked, leading to further structural damage, instability, and potential foundation failure.

Should I buy a house with stair step cracks?

While minor stair-step cracking may be repaired, more severe cracking can indicate serious, expensive underlying foundation problems. Unless you receive confirmation from a foundation repair professional that the issues are minor and repairable, purchasing a home with existing stair-step cracks in the foundation is generally not advisable.

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