How to Repair Foundation Cracks


It is important to understand how to repair foundation cracks. Our house foundations are rigid structures, and over time, may develop cracks for a variety of reasons. As the building settles or the ground shifts, cracks may occur that enable water to enter your home’s basement, crawl space, or other living spaces. One thing that you must not do is to just ignore the cracks that may develop in the foundation. Because your home’s foundation is the structural base of the home, the “platform” it is built on, it is important to repair foundation cracks as soon as they are discovered so that they don’t get any larger or spread open to the point that they weaken the structural integrity of your home or building.

Concrete and concrete blocks will expand and contract due to temperature fluctuations. In the winter they contract with the cold and during the summer they expand with the heat. This movement doesn’t always result in a crack, but when it does you need to take corrective action. When any foundation crack is or becomes large enough to squeeze the tip of your finger into it, the crack is considered a severe crack and it will require immediate attention.

No matter which repair process you consider using, all foundation repairs should be made from the inside of the foundation.

How to Repair Small Concrete Foundation Cracks

  1. Clean the area of the crack using a hammer and chisel if necessary to remove any small chips, debris, and dusty particles.
  2. Use a product specifically designed for concrete foundation cracks.
  3. Lightly mist the crack with water, this will keep the moisture in the patch from being absorbed out into the concrete and stops the patch material from forming a solid bond.
  4. Use a trowel to apply the patching compound to the crack, smoothing it out as much as possible
  5. Immediately wash any patching compound off the tools you used to keep them from being ruined.

How to Repair Small Concrete Block Foundation Cracks

These types of cracks usually occur in the mortar between the individual concrete blocks.

  1. Using a cold chisel and a hammer, chip away the cracked or loose mortar.
  2. Remove the material to a depth of about ½ inch.
  3. Use a brush to apply water to the joints to be repaired.
  4. Apply a mortar patch material for brick and block mortar, forcing the product into the joint.
  5. Wait about 10 days and then seal the joint with an acrylic or silicone masonry sealer.
how to repair foundation cracksStep cracks repaired in basement

Using Epoxy to Repair Foundation Cracks

  1. Clean the crack with a wire brush and make sure that the area to be repaired is dry and not leaking any water at the time of the repair.
  2. Wipe the surface clean to remove any dust.
  3. If any moisture is present you can use a hair dryer or leaf blower to dry the area.
  4. Starting at the bottom of the crack, make a mark every 4-6 inches; these marks will indicate where each injection port will be located.
  5. Using a small amount of the epoxy from an epoxy repair kit, adhere the ports (for injecting the epoxy) along the crack and allow the ports to cure for 15 minutes.
  6. Apply a layer of epoxy approximately 4 inches wide along the length of the crack and mound the epoxy around the base of the injection port.
  7. Using an epoxy injection gun, slowly apply the epoxy into a port, starting with the lowest port and work upward.
  8. After 24 hours the injection ports can be removed by chiseling or grinding.

Using Polyurethane Foam to Repair Foundation Cracks

  1. Clean the crack with a wire brush and make sure that the area to be repaired is dry; the concrete does not have to be completely dry, but should not be actively leaking. If any paint is covering the crack it must be removed.
  2. Wipe the surface clean to remove any dust.
  3. Starting at the bottom of the crack, make a mark every 4-6 inches; these marks will indicate where each injection port will be located. The tighter the crack, the closer together the ports should be. Take care not to cover the port opening with the poly-foam.
  4. Using a small amount of the poly-foam, attach the ports on each mark and allow 10-15 minutes for the ports to set up.
  5. Apply a layer of poly-foam approximately 4 inches wide along the length of the crack and mound the poly-foam around the base of the injection port. Allow the poly-foam to cure for 30-60 minutes.
  6. Squirt water into the ports, beginning at the top. Inject the water in each port until you can see water at the next port down.
  7. Using an injection gun, slowly apply the poly-foam into a port, starting with the lowest port and work upward. Plug each port as you finish injecting into it. As it is injected, the foam expands, activated by the water.

Polyurethane vs. Epoxy

Using epoxy to repair foundation cracks has its drawbacks. Epoxy cannot be applied if the concrete is wet. And why are you repairing the crack? Because water is present and you are trying to stop a leak. So you would have to wait until the concrete and the ground were completely dry. Also, epoxy hardens and that means it is brittle. If the ground shifts again, or if the foundation expands and contracts after the epoxy repair is made, the repair may begin to leak again.

Polyurethane foam remains rubbery. It will flex if the foundation moves or the ground shifts slightly. Since it expands as it is applied and while it cures, it does a better job of filling every inch of the crack. Polyurethane foam does a better job of permanently repairing a foundation crack.

DIY vs. Professional

Sometimes the ambitious do-it-yourselfer can successfully repair smaller foundation cracks. But if you see any cracks that continually reappear, or if foundation walls begin to bulge, you need to contact a foundation repair specialist. If you would like to receive more information about how to repair foundation cracks, free advice is available 24 hours a day. Or if you would like to contact a pre-qualified foundation crack repair specialist, they are also available to talk to 24 hours a day. Either way, all you need to do is call 877-960-0491. Local experts are standing by to help solve your problems with foundation crack repairs.





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Written by Mark Huey.