How to repair foundation cracks (2024 Guide)

Key points

• DIY repair methods include using epoxy injection, polyurethane foam and hydraulic cement.

• Nonstructural cracks don’t affect the foundation’s structural integrity, while structural cracks can lead to significant damage.

• You can repair nonstructural cracks yourself, but structural cracks require professional repair.

Ignoring a foundation crack can lead to costly repairs and compromise your home’s integrity.

You should address foundation cracks immediately to prevent further damage. Whether you notice a crack in your basement wall or crawl space, understanding the best repair methods is essential.

To provide the most reliable advice on foundation crack repairs, we consulted with experts Joshua Parrish, co-owner of Hammer and Handsaw and licensed residential contractor, and Saddat Abid, senior property buyer and CEO at Property Saviour.

This guide will walk you through assessing foundation cracks, gathering necessary supplies and performing DIY repairs. We’ll also cover the signs of more severe issues that suggest it’s time to bring in a foundation professional.

What are foundation cracks?

Foundation cracks are fractures or openings in a home’s foundation walls or floors, often caused by settling, soil pressure or changes in moisture levels.

Understanding the types of foundation cracks is the first step in addressing them and determining the proper repair method. Here are some common types of foundation cracks:

When should you call in a professional?

Structural cracks are serious and require professional intervention, while nonstructural cracks can often be repaired with DIY methods. Here’s how to determine whether the crack falls into the nonstructural or structural category.

Nonstructural cracks

Nonstructural cracks are minor and don’t affect the foundation’s structural integrity. These cracks are often less than 1/8-inch wide and can result from the natural settling of the house, shrinkage of the concrete or minor temperature changes.

Hairline cracks and minor vertical cracks typically fall into this category and can usually be repaired with DIY methods.

If you choose not to fix a small crack right away, it’s best to keep a close eye on it to see if it gets worse. Abid recommended recording your findings and explained, “Documentation is going to be useful, probably with photos and measurements.”

Structural cracks

Structural cracks are more severe and indicate serious issues with the foundation that can lead to significant damage. These cracks are often wider than 1/8 inch and may appear as horizontal, severe diagonal or stair-step patterns.

If you notice cracks accompanied by wall bowing, bulging or significant water leakage, these are undeniable signs of structural damage. You’ll want to consult a structural engineer or foundation repair specialist to assess the situation and recommend appropriate repair methods. A DIY approach won’t be an option.

Sometimes, it can be difficult to differentiate between nonstructural and structural cracks. “Any small ‘hairline’ cracks usually aren’t concerning, but a crack with an angle or pattern like a stair-step in brick or block foundation likely means there could be an issue,” said Parrish. “Also, any crack that allows water to seep in should be addressed.”

What tools and materials do you need for DIY foundation crack repair?

Now that you know your crack doesn’t require professional repair, set yourself up for DIY success by gathering the appropriate tools and materials. You should collect the following:

• Repair kit: A foundation repair kit typically includes all the necessary materials for a first-time DIY repair, including epoxy or polyurethane foam, injection ports and application tools.
• Hydraulic cement: Designed for filling large cracks, hydraulic cement expands when cured to create a tight seal.
• Wire brush: Before applying repair materials, you’ll need a brush to clean cracks of loose debris, paint or old filler.
• Chisel and hammer: These tools widen the crack a bit so the repair material sticks better to the concrete.
• Putty knife: Used for applying and smoothing epoxy, sealant or patching compounds into cracks.
• Trowel: A trowel spreads repair materials evenly and smooths the surface after using hydraulic cement or patching compounds.
• Caulk gun: A caulk gun is needed to inject epoxy or polyurethane into narrow cracks for even application and flow.
• Injection ports: These small plastic nozzles enter the crack to ensure the epoxy or polyurethane fills it completely.
• Polyurethane foam: The flexible material fills cracks that may still move, stopping leaks and sealing cracks in foundation walls.
• Sealant: A high-quality, flexible sealant is often used to prevent water from getting into a repaired crack, adding extra protection.

Step-by-step guide to DIY foundation crack repair

With the proper tools in hand, you can start your foundation repairs. Here’s a step-by-step guide to help you fix foundation cracks using different methods.

Preparing the crack

Before starting any repair, prep the crack so the materials stick well.

1. Scrub the crack with your wire brush to clean it thoroughly. 
2. Gently widen the crack using a chisel and hammer to create a V-shaped groove.
3. Use a vacuum or compressed air to clear dust or debris from the widened crack.
4. Use a damp cloth to lightly moisten the crack with water. Avoid saturating it, as too much water can prevent proper bonding.

Option 1: Using epoxy injection

Epoxy injection is a great way to repair cracks in your foundation. Here’s how to do it.

1. After cleaning the crack, insert plastic injection ports into it, spacing them about 12 inches apart. Then, secure them with epoxy sealer.
2. Use a putty knife to apply epoxy sealer along the entire length of the crack. Cover the bases of the injection ports. Spread the sealer about 1/8-inch thick and 1 inch on either side of the crack.
3. Once the sealer has cured (typically six to 10 hours), mix the epoxy according to the manufacturer’s instructions. Insert the epoxy cartridge into a caulk gun and start injecting at the lowest port. Continue injecting until epoxy oozes out of the port above, then plug the port. Repeat this process for all ports.
4. After the epoxy has cured (usually five days), cut off the protruding parts of the injection ports. If needed, patch the severed ports with additional epoxy sealer.

Option 2: Applying polyurethane foam

Polyurethane foam is flexible and ideal for sealing cracks that might still move. Follow these steps when using this DIY approach.

1. Clean and widen the crack as described in the previous section.
2. Inject the polyurethane foam into the crack using a caulk gun. Start at the bottom and work your way up, ensuring the foam fills the entire crack.
3. Once the foam has expanded and cured, trim any excess foam with a utility knife.
4. Finally, apply a layer of sealant over the foam for added protection.

Option 3: Using hydraulic cement and filler

Hydraulic cement is excellent for filling larger cracks and making a durable repair.

1. Clean and widen the crack as described earlier.
2. Follow the manufacturer’s instructions to mix the hydraulic cement. It should be thick but workable.
3. Use a trowel to press the hydraulic cement into the crack. It should fill the entire void. Smooth the surface with the trowel for a neat finish.
4. Let the hydraulic cement cure according to the manufacturer’s recommendations. Once cured, the repair will be solid and watertight. No other steps or materials are needed.

What’s next?

If you decide to fill foundation cracks yourself, remember that cracks can appear again at any time. The best strategy is to stay vigilant and proactive in preventing them.

Remember the following:

• Keep your foundation properly waterproofed.
• Ensure proper drainage around your home to reduce soil pressure.
• Conduct routine foundation inspections to catch early signs of cracks or damage.
• Address any small cracks immediately to prevent them from becoming larger issues.
• Maintain consistent soil moisture around your home to prevent the expansion and contraction that leads to foundation shrinkage and cracks.
• Clean and maintain your gutters and downspouts to ensure water is directed away from your home’s foundation.

Parrish said that proper gutter drainage and landscape grading will prevent water from accumulating around the home, which could affect the foundation. He also talked about landscaping. “I know a lot of homeowners love having large trees and plants around their home, but they should consider planting trees further away from the foundation. Trees with heavy roots can disrupt the ground and grow under the foundation if it’s too close to the home,” he said.

While preventing every crack is impossible, staying on the lookout and acting quickly can make a significant difference. Should another crack appear, the best approach is promptly diagnosing it and determining whether professional repair is necessary or if another DIY method can be tried. 

Being proactive about repairing foundation cracks will help keep your home safe and stable, giving you peace of mind and preserving your property’s value.

Top local foundation repair companies near you

New York City, N.Y. Los Angeles, Calif. Chicago, Ill. Houston, Texas Phoenix, Ariz. Philadelphia, Pa. San Antonio, Texas San Diego, Calif. Jacksonville, Fla. Columbus, Ohio Indianapolis, Ind. Charlotte, N.C. Louisville, Ky. Seattle, Wash. Denver, Colo. Nashville, Tenn. Washington, D.C. Boston, Mass. Las Vegas, Nev. Austin, Texas