States / Florida
67 counties · median score 62
Crawl space moisture in Florida
Most of Florida sits on soil that holds water: 52 of its 67 counties score high or elevated, led by Hendry County at 77. In much of the state a vented crawl space over bare ground is working against the soil it was built on.
- 1Wettest county Hendry County
- 2High or elevated 52 of 67
- 3Median score 62
- 4Driest county Okaloosa County
Florida's soil, taken as a whole
Across the 34,994,489 acres mapped in these 67 counties, 74% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 77% 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. 62 of the 67 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 9.1% |
| Somewhat excessively drained | 1.5% |
| Well drained | 8.6% |
| Moderately well drained | 7% |
| Somewhat poorly drained | 8.7% |
| Poorly drained | 40.4% |
| Very poorly drained | 24.2% |
| Subaqueous | 0.5% |
Radon. By EPA zone, 0 Florida counties here are zone 1 (highest potential), 9 zone 2 and 57 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 Florida county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Florida numbers
The wettest county, Hendry County, is 72% poorly drained by dominant condition, with a seasonal water table averaging 0.5 ft below grade across the 98% of acres that report one, and sits in EPA radon zone 3. The driest, Okaloosa County, is 43% excessively drained. 36 Florida 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.