How to Repair a Concrete Foundation

foundation in need of repair
  • 1-4 hours
  • Intermediate
  • 0-500
What You'll Need
Circular power saw
Masonry blade
Steel rebar
Shrink-resistant repair mortar
Crack chaser blade
Steel trowel
Water hose
Epoxy gel adhesive
Putty knife
Epoxy resin
Concrete grinder
Leveling compound
Concrete sealant

Ordinarily, concrete foundation repair is not necessary because concrete is a very long lasting material. In fact, some concrete foundations built more than a hundred years ago in Colorado's gold country villages still stand today. Not all concrete foundations are as sturdy and lasting as those ones.

Some deteriorate after years of weather and wear. When they do, they often need to be repaired. If you find yourself needing to repair a concrete foundation, follow these five steps to complete the project.

Step 1 - Remove Damaged Portions

Use a circular saw with a masonry blade to cut and remove the damaged portion of your concrete foundation. If you find steel rebar in the foundation, leave it in place and remove the rust, concrete debris, and dirt which is stuck to it. Replace any damaged rebar with new, clean bars.

In removing the damaged section of concrete, cut out a square of the damaged concrete, with the damaged portion located in the center of the square. Be sure that in cutting the concrete into a square, you make the edges 90°. Leave a one-inch margin between the edge of the square and the damaged concrete.

Step 2 - Fill Cut Out Areas

Use your repair mortar to fill areas where you have removed damaged or deteriorated concrete. Use a steel cement trowel to level the new mortar.

Step 3 - Route Cracks

crack in concrete

Replace the masonry blade in your circular saw with a crack chaser blade, then route open cracks until they are one-inch deep. The surface of the new crack sides should be vertical when you've finished routing.

Use water to flush debris and dirt from the crack, then allow the crack to dry until there is no moisture left in the crack. Ensure that all moisture has evaporated. Moisture prevents the epoxies that you will add in Step 4 from adhering to the surface.

Step 4 - Apply Epoxies

Apply your epoxy gel adhesive to the surfaces of larger cracks with a putty knife. When the adhesive has dried, inject epoxy resin until the crack is completely filled.

Step 5 - Level the Surface

Once the mortar and resin have cured, use a concrete grinder to grind and level the foundation's surface, leaving it slightly rough. Afterwards, wash the entire surface with warm water so that all dirt and debris are washed away.

Pour leveling compound into the foundation until you've covered the entire surface with .5-inches of compound. Trowel the surface level, allow it to dry, then grind it until it has a smooth surface.

To repair other damaged areas of the foundation, follow the same procedure as above, waiting until all epoxies and mortar have completely set before making further cuts in the foundation.