States / South Carolina
46 counties · median score 25
Crawl space moisture in South Carolina
South Carolina is mixed: 18 of 46 counties score high or elevated, concentrated where drainage is poorest — Beaufort County tops the list at 67 — while Oconee County scores just 2. Where you are in the state matters more than the state itself.
- 1Wettest county Beaufort County
- 2High or elevated 18 of 46
- 3Median score 25
- 4Driest county Oconee County
South Carolina's soil, taken as a whole
Across the 19,626,569 acres mapped in these 46 counties, 34% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 56% 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. 46 of the 46 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 4.2% |
| Somewhat excessively drained | 3.2% |
| Well drained | 46.1% |
| Moderately well drained | 12.9% |
| Somewhat poorly drained | 10.4% |
| Poorly drained | 14.1% |
| Very poorly drained | 9.1% |
Radon. By EPA zone, 1 South Carolina counties here are zone 1 (highest potential), 8 zone 2 and 37 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 South Carolina county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the South Carolina numbers
The wettest county, Beaufort County, is 44% very poorly drained by dominant condition, with a seasonal water table averaging 0.8 ft below grade across the 78% of acres that report one, and sits in EPA radon zone 3. The driest, Oconee County, is 98% well drained. 7 South Carolina 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.