How to Stop a Stone Foundation From Leaking

Inspect the exterior of the structure and the surrounding landscape. Look for clogged gutters, downspouts that drain near the structure or soil that slopes toward the foundation.

Address the simple exterior problems if they exist. Remove any debris from gutters that causes water to overflow and extend downspouts so they drain several feet away from the foundation. Regrade the yard so that water flows away from the foundation.

Coat the interior of the stone foundation with masonry sealer. Masonry sealers can be based in tar, cement or silicone and are most suitable for correcting only minor seepage. Apply these materials according to manufacturer instructions.

Excavate the area next to the stone foundation if intensive treatment to the exterior of the foundation is necessary.

Replace or apply waterproofing on the foundation's exterior. Local building codes generally outline suitable waterproofing materials. The area to be waterproofed must be clean and dry, and the surface may require priming or other preparation. Waterproofing options may include polymer-modified asphalt or coal tar polyurethane (both applied as liquids), bentonite clay and sheets of solid waterproof membranes.

Install a subsurface drain at the base of the foundation. Dig a trench with a slope at the bottom of about 1 to 2 percent that leads to an outlet or sump pump. Place a perforated PVC pipe at the bottom of the trench, cover the pipe with at least 12 inches of coarse, clean gravel and lay filter fabric on top of the gravel to block sediment but allow water to pass through.

Back-fill the area next to the foundation with gravel or a well-drained soil. The waterproofing material may need to dry for a certain amount of time before this can be done.