District of Columbia: basement moisture and foundation risk by county
1 counties, ranked by our combined index. Highest combined risk is District of Columbia (41), lowest is District of Columbia (41). The worst soil for foundation cracks specifically is in District of Columbia.
Where in District of Columbia the ground is worse
Every county in the state, coloured by the soil values below. Click a county to open its report; switch what the colour means with the buttons. The pattern is geology, not administration — risk stops at the edge of a physiographic region, not at a county line.
- Low (0–27)
- Moderate (28–49)
- Elevated (50–74)
- High (75–100)
County boundaries: US Census TIGER (public domain), simplified for display. Colours are our index from USDA SSURGO fields where loaded, otherwise from our regional model — each county page states which. How the index is calculated.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| District of Columbia | 41 | 35 | 56 | 30 | Piedmont |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside District of Columbia
State lines are political; soil follows geology. These are the distinct ground types inside District of Columbia and why each behaves the way it does.
Piedmont
Saprolite is weathered rock that keeps its structure, so water moves through it along relict joints unpredictably. The Triassic basins inside the Piedmont are islands of strongly expansive clay.
1 counties: District of Columbia
Page data updated