States / Indiana
92 counties · median score 44
Crawl space moisture in Indiana
Most of Indiana sits on soil that holds water: 57 of its 92 counties score high or elevated, led by Adams County at 73. In much of the state a vented crawl space over bare ground is working against the soil it was built on.
- 1Wettest county Adams County
- 2High or elevated 57 of 92
- 3Median score 44
- 4Driest county Lawrence County
Indiana's soil, taken as a whole
Across the 23,158,624 acres mapped in these 92 counties, 47% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 70% 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. 90 of the 92 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 1.3% |
| Somewhat excessively drained | 2.1% |
| Well drained | 30.9% |
| Moderately well drained | 19.1% |
| Somewhat poorly drained | 23.4% |
| Poorly drained | 16.5% |
| Very poorly drained | 6.8% |
Radon. By EPA zone, 56 Indiana counties here are zone 1 (highest potential), 34 zone 2 and 0 zone 3; 2 are not in the EPA table. With most of the state in zone 1, any crawl-space sealing project here should start with a radon test and be designed to take a radon fan.
Every Indiana county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Indiana numbers
The wettest county, Adams County, is 50% somewhat poorly drained by dominant condition, with a seasonal water table averaging 0.7 ft below grade across the 98% of acres that report one, and sits in EPA radon zone 1. The driest, Lawrence County, is 74% well drained. 20 Indiana 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.