States / Delaware
3 counties · median score 41
Crawl space moisture in Delaware
Most of Delaware sits on soil that holds water: 2 of its 3 counties score high or elevated, led by Kent County at 43. In much of the state a vented crawl space over bare ground is working against the soil it was built on.
- 1Wettest county Kent County
- 2High or elevated 2 of 3
- 3Median score 41
- 4Driest county New Castle County
Delaware's soil, taken as a whole
Across the 1,308,500 acres mapped in these 3 counties, 40% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 60% 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. 3 of the 3 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 2.8% |
| Somewhat excessively drained | 1.9% |
| Well drained | 36.4% |
| Moderately well drained | 18.5% |
| Somewhat poorly drained | 3.4% |
| Poorly drained | 18% |
| Very poorly drained | 17.2% |
| Subaqueous | 1.8% |
Radon. By EPA zone, 0 Delaware counties here are zone 1 (highest potential), 1 zone 2 and 2 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 Delaware county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Delaware numbers
The wettest county, Kent County, is 34% well drained by dominant condition, with a seasonal water table averaging 1.4 ft below grade across the 62% of acres that report one, and sits in EPA radon zone 3. The driest, New Castle County, is 59% well drained. No Delaware 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.