States / Maryland
23 counties · median score 28
Crawl space moisture in Maryland
Maryland is mixed: 5 of 23 counties score high or elevated, concentrated where drainage is poorest — Worcester County tops the list at 63 — while Washington County scores just 14. Where you are in the state matters more than the state itself.
- 1Wettest county Worcester County
- 2High or elevated 5 of 23
- 3Median score 28
- 4Driest county Washington County
Maryland's soil, taken as a whole
Across the 6,624,034 acres mapped in these 23 counties, 25% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 54% 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. 23 of the 23 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Excessively drained | 1% |
| Somewhat excessively drained | 2.2% |
| Well drained | 53.9% |
| Moderately well drained | 17.9% |
| Somewhat poorly drained | 3.1% |
| Poorly drained | 14.4% |
| Very poorly drained | 6.4% |
| Subaqueous | 1% |
Radon. By EPA zone, 8 Maryland counties here are zone 1 (highest potential), 8 zone 2 and 7 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 Maryland county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the Maryland numbers
The wettest county, Worcester County, is 29% poorly drained by dominant condition, with a seasonal water table averaging 0.9 ft below grade across the 86% of acres that report one, and sits in EPA radon zone 3. The driest, Washington County, is 76% well drained. 3 Maryland 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.