Flood Proofing There are several ways to protect a building from flood damage. One is to keep the water away by re-grading your lot or building a small floodwall or earthen berm. Another way is to make your walls waterproof and place watertight closures over the doorways. A third approach is to raise the house above flood levels.Many homes, though not in a floodplain, have sewers that back up into the basement during heavy rains. A plug or standpipe can stop this if the water does not get more than two feet deep. They are sold at hardware stores. For deeper sewer backup, speak to a plumber about...