How to Patch a Concrete Block

Concrete blocks are a strong and versatile building material that's widely used in the construction of walls. Precast and hardened prior to use, the blocks are typically stacked and held in place with mortar. A concrete block wall can last for decades, but damage to a block can weaken the wall. You should patch cracks or holes in a block as you detect the damage and before it spreads. You can patch a damaged block quickly and efficiently using mortar, restoring the wall's strength after the patch cures fully.

• 1

  Remove any scraps of concrete from the damaged area, and then remove dirt and debris using a wire brush.

• 2

  Mix a small batch of mortar in a bucket using an electric drill with a paddle bit attachment, until you have a mix the consistency of peanut butter. Add concrete coloring to the mortar during mixing to match the color of the blocks.

• 3

  Spray the damaged area with water so that the surface is damp. Fill the damaged area with the mortar, using a trowel to force the mortar firmly into the hole or crack in the block in multiple thin layers. Pack the damaged area fully with the mortar and then level the surface of the patch using the flat of the trowel.

• 4

  Allow the patch to cure for a week. Spray the surface of the patch with a hose to keep it moist during the curing period, preventing the mortar from drying out too quickly and losing strength.

• 5

  Paint the patch to match the surrounding block surface if the other blocks in the structure are painted.