- 1). Make a keyhole cut in the crack with a cold chisel and hammer by widening the base of the crack so it is wider than the crack's surface. Make the cut no deeper than a ½ inch. Brush away debris with a wire brush.
- 2). Spray expanding insulating foam from the bottom of the crack up to the top. This will help to prevent water from entering the foundation and damaging it further.
- 3). Follow the hydraulic cement's manufacturer's instructions for mixing. Spread thin layers of hydraulic cement into the crack with a putty knife by starting at the bottom of the crack and working upward. Fill the crack by applying more layers of hydraulic cement until the area is slightly higher than the surrounding foundation.
- 4). Feather out the edges of the repair area with a trowel until the repaired area is flush with the surrounding area. Let the hydraulic cement dry.
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