States / Michigan
79 counties · median score 37
Crawl space moisture in Michigan
Michigan is mixed: 36 of 79 counties score high or elevated, concentrated where drainage is poorest — Bay County tops the list at 72 — while Leelanau County scores just 10. Where you are in the state matters more than the state itself.
- 1Wettest county Bay County
- 2High or elevated 36 of 79
- 3Median score 37
- 4Driest county Leelanau County
Michigan's soil, taken as a whole
Across the 35,999,005 acres mapped in these 79 counties, 45% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 58% of acres report a seasonal water table within about two metres. That is a wet state by any measure; a third or more of its land holds water near the surface for part of the year. 78 of the 79 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 9.1% |
| Somewhat excessively drained | 7.8% |
| Well drained | 26.5% |
| Moderately well drained | 11.2% |
| Somewhat poorly drained | 18.4% |
| Poorly drained | 13% |
| Very poorly drained | 14% |
Radon. By EPA zone, 9 Michigan counties here are zone 1 (highest potential), 32 zone 2 and 38 zone 3. EPA says to test regardless of zone; a sealed crawl space is the cheapest moment to add radon venting if a test calls for it.
Every Michigan county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Michigan numbers
The wettest county, Bay County, is 51% poorly drained by dominant condition, with a seasonal water table averaging 0.3 ft below grade across the 97% of acres that report one, and sits in EPA radon zone 3. The driest, Leelanau County, is 45% well drained. 9 Michigan counties reach the high tier, where poorly drained soils, group D clays and a shallow water table occur together.
The score is a guide to the soil, not to a house: a well-graded lot with working gutters in a high county can have a dry crawl space, and a bad downspout can flood one in a low county. The R408 calculator sizes venting or encapsulation for any footprint.
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted; EPA Map of Radon Zones, county table (June 2024 JSON). Checked 2026-10-23.