If spring has sprung a leak in your basement wall, it is time to head to your local hardware store or lumber yard for some hydraulic cement.
Step 1: Use a chisel to enlarge any cracks bigger than an eighth inch in diameter. Inverted V-shaped cuts will allow the cement to grab behind the wall surface. Make the opening of the crack or hole at least a half inch smaller than the back portion of the hole.
Step 2: Use a stiff wire brush to remove any loose debris. A can of compressed air works well to blow away smaller debris and dust.
Step 3: For dry areas, soak the surface with water before applying the hydraulic cement. Moisture creates a stronger bond by preventing water from being leeched out of the cement and into existing masonry.
Step 4: Following the package instructions, mix clean, cold water into a portion of hydraulic cement. The cement sets up quickly, so only mix what you can use in three minutes or less. Colder water will slow the setting time slightly.
Step 5: For inactive leaks, use a trowel or putty knife to work the hydraulic cement into the crack or hole. Start at the top of the opening and work down toward the floor. Apply pressure to force the cement firmly into the crack or hole. Smooth each patched area with a trowel or putty knife before moving on.
Step 6: For active leaks, roll a small portion of the hydraulic cement in your hands until it becomes warm to the touch. Press the mixture firmly into the crack or hole. Hold the patch in place for three to five minutes and smooth the area with a trowel or putty knife.
Step 7: After the area to be patch has been filled and smoothed, allow it to dry for several days.
Step 8: When the hydraulic cement is thoroughly cured, paint the entire area with a waterproof masonry coating such as Drylock Masonry Treatment by UGL.