How to Repair Stone Foundation Walls


Stone foundation walls are common on many older homes. Although they can look very attractive, the mortar joints are prone to weakening or cracking over time. This causes water leaks that lead to further decay of the mortar. Eventually, you can be left with loose and missing stones, or bulging and collapsing foundation walls. Follow these regular repair and maintenance routines to avoid expensive structural damages.

Things You'll Need

  • Gloves
  • Mortar
  • Trowel
  • Bucket
  • Wire brush
  • Shovel
  • Caution tape
  • Spray cement sealant

Repairing the Exterior

  • Shovel approximately one foot down along the entire length of the exterior stone foundation needing repair. Place noticeable caution tape or flags to indicate the area is being worked on.

  • Inspect the foundation for loose and missing stones or mortar joints. Pull the loose stones from the foundation wall and use a wire brush to clean debris from the hole. Loose debris will adversely affect the new mortar from bonding with the old mortar.

  • Mix the amount of mortar needed according to the package instructions. Use a trowel to place a layer of fresh mortar into the openings that held the loose stones. Replace the stones and smooth out the mortar joints with the trowel. Areas with missing stones will need to be completely filled with mortar.

  • Fill any areas with missing mortar joints by troweling in the cement mixture. Allow three or days to dry and then replace the dirt around the foundation wall.

Repairing the Interior

  • Check the entire interior stone foundation wall for loose or missing stones and cracked or missing mortar. Sweep areas out with a wire brush. Mix the needed amount of mortar for the job following the package instructions. It's always better to be conservative by initially mix too little, rather than too much. More can be made if needed.

  • Use the trowel to re-coat mortar in areas with loose stones. Replace all the stones and smooth out the mortar joints. Refill all areas with missing mortar joints and stones with the new mixture.

  • Allow a month for the exterior and interior mortar to cure. Spray cement sealant on the stone foundation. Concentrate the sealant on the mortar joints and repaired areas.

Tips & Warnings

  • Run wire brush along all mortar joints. It is sometimes hard to detect loose joints visually. Place additional mortar around joints that are near areas where water seems to collect.
  • Use gloves when working with cement products because they can chemically burn skin. Follow safety precautions on the cement sealant label.


  • Photo Credit The image is courtesy of the Photobucket photo pool.
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