What Are the Steps to Repairing Crumbling Basement Walls?

To repair crumbling basement walls, remove the old mortar, clean the walls with a wire brush and repair with new mortar. The type of mortar used is dependent on the type of stone used in the wall as well as the condition of the stone itself.

Basement walls made of stone are common in many older homes. The walls were built to expand and contract with the temperature of the soil. Over time, this leads to deterioration and crumbling of the mortar and, sometimes, the stones as well. While it is best to have an experienced stonemason do the repairs, the steps are quite simple.

  1. Remove the crumbling mortar
  2. Use a hammer to gently tap on the mortar surrounding the stones. A hollow sound indicates an area that needs to be replaced. Use a chisel to dig out the crumbling mortar, stopping once solid mortar is reached. Repeat until all of the old mortar is removed.

  3. Clean the wall
  4. Use a wire brush to clean the wall. This removes any loose mortar that might remain, and it preps the surface for the application of the new mortar.

  5. Apply the new compound
  6. Mix the new mortar compound according to package directions. Another good mix is one part cement to three-quarters part limestone, sand and water. Mix that to the consistency of pancake batter, and pack the joints of the stones.