How To Fix a Basement Leak

Sand the surface of the wall on the inside of your basement with sandpaper to remove any paint. The patching and waterproofing compounds will not adhere correctly to painted surfaces.

Mix one part cement and two parts sand with water in a bucket. The mixture should form a stiff paste-like mortar.

Spread a thin layer of the sand and cement mortar onto any cracks and holes on the inside of the basement foundation using a mortar trowel. Cover all areas thoroughly and extend mortar about 2 inches beyond the edges of the cracks and holes. Allow the area to dry overnight.

Spray the wall with water using a garden hose. The area should be damp, however there should not be water droplets on the surface of the wall.

Prepare the waterproofing mixture according to the package directions in a large bucket. It should be a slightly thick slurry when it is mixed properly.

Using a circular motion, apply the mixture to the wall in the area that is showing signs of leakage, starting at the bottom and working to the top. The mixture should extend at least 2 inches beyond the leak affected areas and should be tapered off at edges.

Spray the area down the repaired area with water once it is dry to touch (It should not rub off onto your hand). The area should be completely saturated. Leave the area to rest overnight.

Thoroughly wet the waterproofed area with water again. It should be very damp, but not dripping with water.

Apply a second coating of waterproofing mixture. Use the same technique as the first coat, taking care to feather the edges about 2 inches from the leaking area. Allow entire surface to dry at least 24 hours.