States / Missouri
113 counties · median score 39
Crawl space moisture in Missouri
Missouri is mixed: 54 of 113 counties score high or elevated, concentrated where drainage is poorest — Audrain County tops the list at 80 — while Carter County scores just 11. Where you are in the state matters more than the state itself.
- 1Wettest county Audrain County
- 2High or elevated 54 of 113
- 3Median score 39
- 4Driest county Carter County
Missouri's soil, taken as a whole
Across the 44,226,846 acres mapped in these 113 counties, 32% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 66% 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. 113 of the 113 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 1% |
| Somewhat excessively drained | 8.2% |
| Well drained | 29.5% |
| Moderately well drained | 29.1% |
| Somewhat poorly drained | 18.3% |
| Poorly drained | 12.1% |
| Very poorly drained | 0.5% |
| Subaqueous | 1.4% |
Radon. By EPA zone, 11 Missouri counties here are zone 1 (highest potential), 94 zone 2 and 7 zone 3; 1 are not in the EPA table. 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 Missouri county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Missouri numbers
The wettest county, Audrain County, is 73% poorly drained by dominant condition, with a seasonal water table averaging 0.9 ft below grade across the 99% of acres that report one, and sits in EPA radon zone 2. The driest, Carter County, is 46% somewhat excessively drained. 15 Missouri 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.