States / Alabama
67 counties · median score 22
Crawl space moisture in Alabama
Most of Alabama drains well: only 4 of 67 counties score high or elevated, and the median is 22. Montgomery County is the exception at 47; crawl-space moisture problems here usually come from grading, gutters and plumbing rather than the soil itself.
- 1Wettest county Montgomery County
- 2High or elevated 4 of 67
- 3Median score 22
- 4Driest county Cleburne County
Alabama's soil, taken as a whole
Across the 33,059,769 acres mapped in these 67 counties, 16% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 35% of acres report a seasonal water table within about two metres. That is a middling figure: wet ground is common in valleys and lowlands but far from universal. 67 of the 67 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 0.5% |
| Somewhat excessively drained | 6% |
| Well drained | 63.6% |
| Moderately well drained | 13.9% |
| Somewhat poorly drained | 9.1% |
| Poorly drained | 5.9% |
| Very poorly drained | 1.1% |
Radon. By EPA zone, 13 Alabama counties here are zone 1 (highest potential), 33 zone 2 and 21 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 Alabama county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Alabama numbers
The wettest county, Montgomery County, is 33% well drained by dominant condition, with a seasonal water table averaging 1.4 ft below grade across the 55% of acres that report one, and sits in EPA radon zone 2. The driest, Cleburne County, is 100% well drained. No Alabama county reaches the high tier.
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.