Basements and the lower floors of split levels can be protected from surface water by construction of low walls around stairwells or using backfill. First, a waterproofing compound is applied to the walls. Walls are built up around the window wells (don’t block basement windows that are needed for emergency exits). An earthen berm can be filled against the side of the house.

A subsurface drain and one or two correctly sized sump pumps are a must. The drains and pumps can keep up with the seepage before it gets through the berm and reaches your house.

The secret is to not let floodwaters touch the house. If water on the surface of the ground gets up against the house, it probably will seep down the gap between the basement walls and the surrounding soil. This will greatly increase the amount of water pressure against the basement.

Sump pumps cannot keep up with surface water. If you have sandy or permeable soil, you should consult an engineer or soils expert to ensure that the berm will extend far enough away from the walls. Don’t forget: filling or grading in your yard requires a permit.

Precautions. The berm can only be built so high. It can be overtopped by a flood higher than expected. Being made of earth, it is susceptible to erosion from rain and floodwaters if not properly sloped and covered with grass and maintained. A berm can settle over time, lowering its protection level. The small floodwalls can crack, weaken, and lose their watertight seal.

You also need to account for water in the sewer lines, footing drain and sump pump outfall. They may carry water under the barrier and flood inside your house.

Suggested reading: Rebuild and Floodproof – Red Cross

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Cook County Sheriff Emergency Management Agency
1311 Maybrook Drive • Maywood, Illinois 60153
708.865.4766
ccsema@cookcountysheriff.org