Concrete Block Foundation: How to Repair a Collapsed Base

What You'll Need
Circular power saw with masonry blade
Repair mortar (preferably shrink-resistant)
Putty knife
Steel rebar
Water hose
Epoxy resin and gel adhesive
Putty knife
Concrete grinder and sealant
Leveling compound

Concrete block foundation repair is needed when a concrete block foundation collapses. However, since this is a rare occurrence, ordinarily, such a repair is not necessary. Regardless, although concrete is a long lasting material, it is possible that the foundation may collapse with age. Fortunately, concrete block foundations can be repaired. Here’s how you can repair a collapsed concrete foundation base.

Step 1 – Remove the Collapsed Portions

You will need to use the power saw and the masonry blade to cut out the portions that have collapsed. With both your hands, remove the concrete debris and dirt that you may find inside. If there are any damaged steel rebar with the concrete, you should remove it as well. Ideally, you should cut out the damaged portion in a square, right at the center of the area where the concrete blocks have collapsed. Take out all the unnecessary debris and clean the area completely. Cut the collapsed portions at 90 degree angles so that you can insert a new concrete block in a clean and efficient manner.

Step 2 – Fill out the Damaged Area

You will now have to fill out the areas that have been damaged. Measure the square that you have cut in and mix mortar accordingly. The mortar will be used to fill in all the areas from where the deteriorated concrete has been removed. You can then use a trowel to lay a layer of mortar and level it.

Step 3 – Treat the Cracks

There is a high likelihood that you may have several cracks in the foundation as well. Use the circular saw to route the cracks, making them at least 1-inch deep. The surfaces of the cracked sides should ideally be vertical. With the water hose, flush out the debris before filling in the cracks. Allow the cracks to dry.

Step 4 – Seal the Cracks

To seal the cracks, use an epoxy gel adhesive. You can apply the adhesive to the surfaces of the cracks that appear to be large, using a putty knife. Allow the adhesive to dry out before injecting the epoxy resin. Keep injecting till the crack is completely filled.

Step 5 – Level the Foundation

After allowing the mortar and resin to dry completely, grind the concrete foundation surface and level it using a concrete grinder. Grind till the surface seems to be completely leveled. Once you have finished, wash the surface with water so that no dirt or concrete debris remains. Allow the surface to be dry, and then pour the leveling compound on the surface and use a trowel to level the surface. Allow the surface to dry out completely. You may have to leave the compound over night on the surface. Once everything is dry, grind the surface until it becomes smooth.