Cracks in Cinder Block Foundations

Examine all of the walls of your home's foundation. If you notice that cracks are forming in many places, you may have a serious structural issue with your foundation. Call a building or housing inspector to look at your cinder blocks. If there is a major problem, you may have to hire a professional to rebuild the foundations. If there are are but a few small cracks, you can repair them yourself.

Put on a pair of safety glasses.

Undercut the crack using a hammer and a small masonry chisel. Use the chisel to widen the bottom of the crack. Tap the chisel with the hammer along the bottom edges until the crack is slightly larger at the bottom than it is at the top. The crack should resemble a dovetail , as it tapers from narrow down to wide at the bottom. The extra space at the bottom of the crack will give the concrete epoxy a place to expand as it dries and will prevent it from ejecting itself out of the crack as it hardens.

Remove any paint or primer from around the edges of the crack with a wire brush.

Place the nozzle of a tube of concrete epoxy at the top of the crack. Fill the crack in with the epoxy, moving from the top of the crack down to the bottom. Apply enough epoxy so that it is flush with the surface of the cinder block. Allow the concrete epoxy to dry before proceeding.

Sand the epoxy down with a fine-grit sandpaper until it is even with the surface of the cinder block. The epoxy will expand as it dries, but sanding the hardened epoxy will quickly allow you to remove the excess.

Wait two to three weeks before repainting the repaired cinder block. Paint or primer will not properly adhere to the repaired area if you attempt to paint too soon.