States / District of Columbia
1 counties · median score 9
Crawl space moisture in District of Columbia
Most of District of Columbia drains well: only 0 of 1 counties score high or elevated, and the median is 9. District of Columbia is the exception at 9; crawl-space moisture problems here usually come from grading, gutters and plumbing rather than the soil itself.
- 1Wettest county District of Columbia
- 2High or elevated 0 of 1
- 3Median score 9
- 4Driest county District of Columbia
District of Columbia's soil, taken as a whole
Across the 44,160 acres mapped in these 1 counties, 2% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 10% of acres report a seasonal water table within about two metres. That is a dry figure; wet soils here are confined to river bottoms and wetlands. 1 of the 1 counties have mapped soils subject to occasional or frequent flooding.
| Drainage class | Share of mapped acres |
|---|---|
| Somewhat excessively drained | 7.6% |
| Well drained | 77.7% |
| Moderately well drained | 12.9% |
| Poorly drained | 1.6% |
| Very poorly drained | 0.2% |
Radon. By EPA zone, 0 District of Columbia counties here are zone 1 (highest potential), 0 zone 2 and 1 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 District of Columbia county
Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.
What drives the District of Columbia numbers
The wettest county, District of Columbia, is 78% well drained by dominant condition, with a seasonal water table averaging 2.1 ft below grade across the 10% of acres that report one, and sits in EPA radon zone 3. The driest, District of Columbia, is 78% well drained. No District of Columbia 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.