South Carolina: basement moisture and foundation risk by county
46 counties, ranked by our combined index. Highest combined risk is Florence County (52), lowest is Pickens County (26). The worst soil for foundation cracks specifically is in Cherokee County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Florence County | 52 | 43 | 44 | 82 | Southern Atlantic Coastal Plain |
| Cherokee County | 49 | 38 | 66 | 46 | Piedmont |
| Chesterfield County | 49 | 42 | 46 | 66 | Southern Atlantic Coastal Plain |
| Darlington County | 49 | 44 | 45 | 66 | Southern Atlantic Coastal Plain |
| Marion County | 49 | 43 | 44 | 66 | Southern Atlantic Coastal Plain |
| Lee County | 48 | 40 | 36 | 82 | Southern Atlantic Coastal Plain |
| Calhoun County | 47 | 40 | 43 | 66 | Southern Atlantic Coastal Plain |
| Colleton County | 47 | 40 | 42 | 66 | Southern Atlantic Coastal Plain |
| Sumter County | 47 | 43 | 39 | 66 | Southern Atlantic Coastal Plain |
| York County | 47 | 37 | 61 | 46 | Piedmont |
| Barnwell County | 46 | 37 | 60 | 46 | Piedmont |
| Dillon County | 46 | 42 | 37 | 66 | Southern Atlantic Coastal Plain |
| Georgetown County | 45 | 42 | 35 | 66 | Southern Atlantic Coastal Plain |
| Jasper County | 45 | 37 | 55 | 46 | Piedmont |
| Marlboro County | 45 | 42 | 33 | 66 | Southern Atlantic Coastal Plain |
| Charleston County | 44 | 40 | 21 | 82 | Southern Atlantic Coastal Plain |
| McCormick County | 44 | 34 | 57 | 46 | Piedmont |
| Berkeley County | 43 | 40 | 45 | 46 | Southern Atlantic Coastal Plain |
| Greenwood County | 43 | 36 | 50 | 46 | Piedmont |
| Horry County | 43 | 44 | 39 | 46 | Southern Atlantic Coastal Plain |
| Clarendon County | 42 | 42 | 24 | 66 | Southern Atlantic Coastal Plain |
| Dorchester County | 42 | 44 | 35 | 46 | Southern Atlantic Coastal Plain |
| Hampton County | 42 | 37 | 45 | 46 | Piedmont |
| Kershaw County | 41 | 43 | 36 | 46 | Southern Atlantic Coastal Plain |
| Richland County | 41 | 38 | 42 | 46 | Piedmont |
| Fairfield County | 40 | 39 | 37 | 46 | Piedmont |
| Newberry County | 40 | 38 | 51 | 30 | Piedmont |
| Saluda County | 40 | 37 | 52 | 30 | Piedmont |
| Bamberg County | 39 | 37 | 49 | 30 | Piedmont |
| Beaufort County | 39 | 40 | 34 | 46 | Southern Atlantic Coastal Plain |
| Orangeburg County | 39 | 39 | 35 | 46 | Piedmont |
| Lexington County | 38 | 38 | 43 | 30 | Piedmont |
| Lancaster County | 37 | 41 | 26 | 46 | Southern Atlantic Coastal Plain |
| Williamsburg County | 37 | 42 | 23 | 46 | Southern Atlantic Coastal Plain |
| Greenville County | 36 | 34 | 32 | 46 | Blue Ridge Mountains |
| Laurens County | 36 | 35 | 43 | 30 | Piedmont |
| Allendale County | 35 | 38 | 34 | 30 | Piedmont |
| Chester County | 35 | 38 | 33 | 30 | Piedmont |
| Edgefield County | 35 | 37 | 36 | 30 | Piedmont |
| Oconee County | 35 | 33 | 30 | 46 | Blue Ridge Mountains |
| Union County | 35 | 36 | 47 | 16 | Piedmont |
| Abbeville County | 33 | 31 | 39 | 30 | Blue Ridge Mountains |
| Spartanburg County | 32 | 36 | 37 | 16 | Piedmont |
| Aiken County | 31 | 37 | 33 | 16 | Piedmont |
| Anderson County | 29 | 31 | 24 | 30 | Blue Ridge Mountains |
| Pickens County | 26 | 31 | 16 | 30 | Blue Ridge Mountains |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside South Carolina
State lines are political; soil follows geology. These are the distinct ground types inside South Carolina 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.
21 counties: Aiken County, Allendale County, Bamberg County, Barnwell County, Cherokee County, Chester County, Edgefield County, Fairfield County, Greenwood County, Hampton County, Jasper County, Laurens County, Lexington County, McCormick County, Newberry County, Orangeburg County, Richland County, Saluda County, Spartanburg County, Union County, York County
Southern Atlantic Coastal Plain
Low, flat and wet. Groundwater sits close to the surface for much of the year, which is why houses here sit on slabs or piers rather than over basements. Where clays are present they are moderately expansive; where sand dominates, the risk is moisture, not movement.
20 counties: Beaufort County, Berkeley County, Calhoun County, Charleston County, Chesterfield County, Clarendon County, Colleton County, Darlington County, Dillon County, Dorchester County, Florence County, Georgetown County, Horry County, Kershaw County, Lancaster County, Lee County, Marion County, Marlboro County, Sumter County, Williamsburg County
Blue Ridge Mountains
Steep ground with deep weathering. Volume change is low, but slope stability is not: colluvium on a mountainside can creep, and debris flows during hurricane rainfall are a documented hazard. A house benched into a slope collects water behind its uphill wall.
5 counties: Abbeville County, Anderson County, Greenville County, Oconee County, Pickens County
Page data updated