Oregon: basement moisture and foundation risk by county
36 counties, ranked by our combined index. Highest combined risk is Coos County (53), lowest is Sherman County (20). The worst soil for foundation cracks specifically is in Clatsop County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Coos County | 53 | 37 | 79 | 46 | Pacific Coast Ranges |
| Clackamas County | 49 | 46 | 40 | 66 | Puget Sound and Willamette Lowland |
| Clatsop County | 49 | 34 | 83 | 30 | Pacific Coast Ranges |
| Douglas County | 49 | 35 | 82 | 30 | Pacific Coast Ranges |
| Lincoln County | 49 | 34 | 71 | 46 | Pacific Coast Ranges |
| Curry County | 48 | 37 | 75 | 30 | Pacific Coast Ranges |
| Yamhill County | 48 | 46 | 39 | 66 | Puget Sound and Willamette Lowland |
| Benton County | 46 | 45 | 34 | 66 | Puget Sound and Willamette Lowland |
| Marion County | 46 | 46 | 32 | 66 | Puget Sound and Willamette Lowland |
| Josephine County | 45 | 34 | 71 | 30 | Pacific Coast Ranges |
| Columbia County | 43 | 44 | 25 | 66 | Puget Sound and Willamette Lowland |
| Hood River County | 43 | 44 | 24 | 66 | Puget Sound and Willamette Lowland |
| Washington County | 43 | 45 | 25 | 66 | Puget Sound and Willamette Lowland |
| Lane County | 42 | 48 | 31 | 46 | Puget Sound and Willamette Lowland |
| Linn County | 41 | 44 | 20 | 66 | Puget Sound and Willamette Lowland |
| Multnomah County | 41 | 45 | 17 | 66 | Puget Sound and Willamette Lowland |
| Tillamook County | 39 | 37 | 59 | 16 | Pacific Coast Ranges |
| Polk County | 38 | 47 | 20 | 46 | Puget Sound and Willamette Lowland |
| Harney County | 36 | 32 | 45 | 30 | Columbia Plateau and Palouse |
| Crook County | 34 | 30 | 43 | 30 | Columbia Plateau and Palouse |
| Gilliam County | 34 | 32 | 39 | 30 | Columbia Plateau and Palouse |
| Grant County | 34 | 30 | 44 | 30 | Columbia Plateau and Palouse |
| Union County | 33 | 30 | 39 | 30 | Columbia Plateau and Palouse |
| Morrow County | 31 | 34 | 29 | 30 | Columbia Plateau and Palouse |
| Baker County | 30 | 30 | 30 | 30 | Columbia Plateau and Palouse |
| Wheeler County | 30 | 30 | 29 | 30 | Columbia Plateau and Palouse |
| Malheur County | 29 | 35 | 20 | 30 | Columbia Plateau and Palouse |
| Deschutes County | 28 | 30 | 23 | 30 | Sierra Nevada and Cascades |
| Jackson County | 28 | 28 | 26 | 30 | Sierra Nevada and Cascades |
| Umatilla County | 28 | 30 | 24 | 30 | Columbia Plateau and Palouse |
| Klamath County | 27 | 26 | 26 | 30 | Sierra Nevada and Cascades |
| Wallowa County | 27 | 31 | 19 | 30 | Columbia Plateau and Palouse |
| Lake County | 26 | 28 | 20 | 30 | Sierra Nevada and Cascades |
| Jefferson County | 24 | 29 | 14 | 30 | Sierra Nevada and Cascades |
| Wasco County | 24 | 27 | 16 | 30 | Sierra Nevada and Cascades |
| Sherman County | 20 | 28 | 13 | 16 | Sierra Nevada and Cascades |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside Oregon
State lines are political; soil follows geology. These are the distinct ground types inside Oregon and why each behaves the way it does.
Columbia Plateau and Palouse
Deep permeable loess on rolling hills, with basalt below. Water table deep, shrink-swell low. Loess is erodible and can settle under load when saturated, so a broken downspout does more damage here than the climate does.
11 counties: Baker County, Crook County, Gilliam County, Grant County, Harney County, Malheur County, Morrow County, Umatilla County, Union County, Wallowa County, Wheeler County
Puget Sound and Willamette Lowland
The one part of the West where basements are genuinely common — and the reason they leak is glacial: dense Vashon till under a permeable cap perches water just above it through the wet season. Volume change is low. Drainage, and hillside seepage, decide everything.
11 counties: Benton County, Clackamas County, Columbia County, Hood River County, Lane County, Linn County, Marion County, Multnomah County, Polk County, Washington County, Yamhill County
Pacific Coast Ranges
Some of the most expansive soils in North America sit here, on some of the least stable slopes. Winter rain saturates clay-rich colluvium and it moves — which is why hillside foundation work on the California and Oregon coast is engineered rather than standardised.
7 counties: Clatsop County, Coos County, Curry County, Douglas County, Josephine County, Lincoln County, Tillamook County
Sierra Nevada and Cascades
Coarse material over rock. Volume change is minimal and drainage is good; the seasonal problem is snowmelt arriving at foundations faster than it can be led away, not a water table.
7 counties: Deschutes County, Jackson County, Jefferson County, Klamath County, Lake County, Sherman County, Wasco County
Page data updated