Solving Mortar Problems in Your Stone Foundation

Even though they are rarely seen on new properties, stone foundations are common in older buildings. They have a special appearance; learning how to solve stone foundation mortar problems will help to protect the health of your property.

Any damage such as weak mortar joints and cracked or loose stones can result in further damage. Cracks in the foundation allows water to penetrate further into the foundation, which can wash away mortar and shift stones as it freezes in cold weather. Replacing lost mortar and protecting against water penetration will protect your foundation against long term damage.


Inspect the quality and the condition of the exposed portions of your stone foundation. Spot any damage as early as soon as possible. The earlier you catch the damage, the easier it will be to repair. Keep an eye out for any broken stones, loose stones, or mortar problems. Inspection of the walls in the basement will often give you a good idea of your foundation health. If the mortar is cracked, damaged, or missing, then you will have o take corrective action.

Loose Stones

If there are any loose stones in the foundation, carefully slide them from the hole in preparation for repairs. It's a good idea to leave them close to the original location, because you don't want to have to worry about doing a huge jigsaw and figuring out where all the stones go. A wire brush can be used remove debris from inside the holes and on top of the individual stones. Use water to clean the entire hole.

Removing Old Mortar

The old mortar needs to be removed with a chisel and a hammer. Do so carefully to avoid causing further damage to the wall. Carefully chip away at the mortar and start scraping it out. The old mortar should come out very easily if it is already cracked or damaged. At a crack, remove the mortar around the crack with the chisel and hammer. Carve a .5-inch wide path along the visible length of the crack.

Mixing Mortar

Once you've prepared the wall, mix a new batch of mortar. Follow the instructions on the packet to create a strong mix. Put the mortar not only into the gaps which you have chipped out but also around the holes where you have removed stones. Apply a layer of mortar to the loose stones and slide them back into the hole. Use a trowel can on both sides to remove any extra mortar.

If there are any small stones which have been removed from the wall, then this whole section can be filled using mortar if desired. To do so, use the flat edge of your trowel to ensure that it's level with the wall.


Once you've finished your repairs, it's a good idea to spray the repairs with concrete sealant. It will protect the mortar from future water damage and various other problems.

Regular maintenance to your stone foundations makes it much easier to keep them in good condition. Get into the habit of regularly checking and maintaining the stone wall before serious problems arise.