New Hampshire: basement moisture and foundation risk by county
10 counties, ranked by our combined index. Highest combined risk is Carroll County (44), lowest is Coos County (29). The worst soil for foundation cracks specifically is in Carroll County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Carroll County | 44 | 43 | 30 | 66 | Glaciated New England upland |
| Belknap County | 43 | 42 | 28 | 66 | Glaciated New England upland |
| Cheshire County | 43 | 42 | 29 | 66 | Glaciated New England upland |
| Strafford County | 41 | 40 | 24 | 66 | Glaciated New England upland |
| Grafton County | 37 | 42 | 23 | 46 | Glaciated New England upland |
| Merrimack County | 33 | 42 | 12 | 46 | Glaciated New England upland |
| Rockingham County | 32 | 43 | 19 | 30 | Glaciated New England upland |
| Hillsborough County | 31 | 40 | 19 | 30 | Glaciated New England upland |
| Sullivan County | 30 | 43 | 13 | 30 | Glaciated New England upland |
| Coos County | 29 | 40 | 14 | 30 | Glaciated New England upland |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside New Hampshire
State lines are political; soil follows geology. These are the distinct ground types inside New Hampshire and why each behaves the way it does.
Glaciated New England upland
A hardpan under thin till creates a perched water table — water stands above an impermeable layer even though the regional water table is deep. It is the commonest cause of a wet basement in New England. Expansive clay is largely absent.
10 counties: Belknap County, Carroll County, Cheshire County, Coos County, Grafton County, Hillsborough County, Merrimack County, Rockingham County, Strafford County, Sullivan County
Page data updated