How to Build a Watertight Basement Wall

Install a good gravel drainage system at the base of the perimeter basement walls; they should be deep enough to go past the footing under the wall. Make it firm but leave enough space between stones that water can filter through. Put perforated plastic pipe in this bed at the junction of the wall and footing to catch and drain water to areas in the lawn or away from the house foundation. Place these protective systems around all walls, draining away from the house.

Seal the exterior of the wall with a good moisture-proofing compound. Use a traditional asphaltic or black tar material or one of the newer polymer-based products; polymers are preferable and will last longer. Apply these materials to seal all the pores in the concrete basement wall.

Backfill the dirt around the foundation to slope away from the house so no water will collect right at the top of the wall. Make sure there are no dips or holes that will retain water near the basement wall. Install gutters and downspouts on all roof edges, with spouts running far away from the house to carry water away from the basement walls.

Paint the interior of the basement walls with a good waterproofing paint, preferably a cement-based type which will fill tiny pores in the concrete to block any seepage from outside.