How to Repair a Stone Foundation

A stone foundation is a traditional architectural element that lends an aura of grace and antiquity to American homes dating from the colonial period to the 19^th century. Even modern homes may have stone foundations, because in addition to providing strong structural support for a home, they have a distinctive, old world charm about them. The problem with stone foundations is that, due to the particularity of this style of masonry, where large stones are essentially cobbled together with mortar, over time the stones can become loose and even fall out of place, and the mortar can start to crumble as well. This leads to a host of problems, from sagging, buckling floors to water leaking into the foundation, causing even more structural damage and leading to mold and other unpleasantness. If you’ve noticed any of these problems in your home, the good news is that you can repair your stone foundation yourself, although it is rather labor intensive. Just read the steps below to find out how.

Step 1 – Dig Deep

In order to repair your stone foundation, you need to tackle the problem from both the inside and the outside. Start with the exterior. First, use your shovel to dig out a 1-foot deep trench along the perimeter of the stone foundation.

Step 2 – Assess the Damage

Your problem is most likely that stones have become loose and out of place, so now that you can see deep to the bottom of the foundation, inspect the situation and assess the damage.

Step 3 – Clean it Up

Take any loose stones that you find out of the wall. Use your wire brush to scrub out any dirt and debris, so that you’ll have a clean surface on which to apply the mortar; otherwise, you’ll just be asking for problems down the road.

Step 4 – Mix the Mortar

Prepare the mortar according to the manufacturer’s directions. Dump it into a large bucket, and mix with water as specified.

Step 5 – Apply the Mortar

Take your trowel and spread a thick layer of the wet mortar in the areas where you removed the loose stones. Put the stones back in, and apply mortar to the areas around the stones, smoothing out the surface with the trowel. Should any stones be missing, fill the gaps in completely with mortar. Also take this opportunity to look for any areas of crumbling mortar that you can touch up.

Step 6 – Let Dry

Let the mortar dry for a minimum of 3 days. Then shovel dirt back into the trench around the house.

Step 7 – Repeat on the Interior

Now that the exterior of the foundation has been taken care of, take a look at the interior, and repeat steps 2 through 6. Look for loose stones, clean out the gaps, apply mortar, and let dry.

Step 8 – Apply Sealant

Once the repair work has been done, wait for at least one month so that the mortar can dry completely. Then, take your specially formulated cement sealant (available at your local hardware store) and spray it over the entire foundation to prevent future problems. Take extra care to apply plenty of sealant to the areas that had been damaged.