Wet basements

Keep surface water away first

The residential building code requires lots to drain surface water away from foundation walls, with the ground falling at least 6 inches in the first 10 feet (ICC, 2024 IRC). University of Minnesota Extension recommends a steeper slope: at least 1 inch per foot for at least 6 feet (UMN Extension).

Downspouts are where the sources disagree most. UMN Extension calls for at least one downspout per 50 feet of eave, with extensions that discharge at least 4 feet beyond the wall (UMN Extension). EPA's building guidance asks for sloped leaders that carry the water at least 10 feet from the foundation (EPA).

When the water comes from below

Saturated soil pushes on basement walls with hydrostatic pressure, which grows with depth, so basement walls take more pressure than the walls above them, and the weight of the wet soil adds to it (FEMA P-312). A sump pit relies on a pump to lift the water outside, and that pump can fail (UMN Extension).

A dehumidifier treats the humidity and the smell, not the water. UMN Extension warns that in a basement with a moisture problem it can make the damage worse (UMN Extension).

Where the water table is shallow

USDA's soil survey flags a saturated zone within about 6 feet of the surface for part of the year as a limit for basements. Counties with 50,000 or more homes where it covers the most land:

Ohio cities

Ohio cities with 5,000 or more homes, measured inside city limits. What waterproofing costs.