Maryland: basement moisture and foundation risk by county
24 counties, ranked by our combined index. Highest combined risk is Prince George's County (47), lowest is Garrett County (31). The worst soil for foundation cracks specifically is in Prince George's County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Prince George's County | 47 | 34 | 66 | 46 | Piedmont |
| Caroline County | 44 | 40 | 34 | 66 | Atlantic coastal plain |
| Charles County | 44 | 35 | 56 | 46 | Piedmont |
| Calvert County | 43 | 41 | 30 | 66 | Atlantic coastal plain |
| Dorchester County | 43 | 39 | 32 | 66 | Atlantic coastal plain |
| Howard County | 43 | 39 | 48 | 46 | Piedmont |
| Allegany County | 41 | 34 | 47 | 46 | Ridge and Valley |
| Carroll County | 41 | 39 | 39 | 46 | Piedmont |
| Kent County | 41 | 39 | 25 | 66 | Atlantic coastal plain |
| Somerset County | 41 | 39 | 25 | 66 | Atlantic coastal plain |
| Anne Arundel County | 40 | 41 | 34 | 46 | Atlantic coastal plain |
| Baltimore County | 40 | 43 | 30 | 46 | Atlantic coastal plain |
| Wicomico County | 40 | 41 | 21 | 66 | Atlantic coastal plain |
| Montgomery County | 39 | 39 | 46 | 30 | Piedmont |
| Baltimore City | 38 | 40 | 28 | 46 | Atlantic coastal plain |
| St. Mary's County | 38 | 39 | 18 | 66 | Atlantic coastal plain |
| Worcester County | 36 | 39 | 26 | 46 | Atlantic coastal plain |
| Cecil County | 35 | 38 | 34 | 30 | Piedmont |
| Harford County | 35 | 35 | 48 | 16 | Piedmont |
| Washington County | 35 | 33 | 31 | 46 | Ridge and Valley |
| Talbot County | 33 | 39 | 14 | 46 | Atlantic coastal plain |
| Frederick County | 32 | 37 | 37 | 16 | Piedmont |
| Garrett County | 31 | 34 | 39 | 16 | Appalachian Plateau |
| Queen Anne's County | 31 | 39 | 20 | 30 | Atlantic coastal plain |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside Maryland
State lines are political; soil follows geology. These are the distinct ground types inside Maryland and why each behaves the way it does.
Atlantic coastal plain
Extremely variable over short distances: sand and saturated clay side by side. A county figure means less here than anywhere else we cover — the individual parcel decides.
13 counties: Anne Arundel County, Baltimore County, Baltimore City, Calvert County, Caroline County, Dorchester County, Kent County, Queen Anne's County, Somerset County, St. Mary's County, Talbot County, Wicomico County, Worcester County
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.
8 counties: Carroll County, Cecil County, Charles County, Frederick County, Harford County, Howard County, Montgomery County, Prince George's County
Ridge and Valley
Limestone valleys mean karst: permeability is excellent until it is not. Sinkhole activity is an underrated cause of foundation failure here.
2 counties: Allegany County, Washington County
Appalachian Plateau
Water travels over bedrock under a thin skin of colluvium. A house cut into a hillside has an entire catchment behind its uphill wall — what decides the outcome here is a daylight drain, not a coating.
1 counties: Garrett County
Page data updated