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Chester County, Pennsylvania
A shallow water table limits basements on 21% of Chester County's mapped land. Shrink-swell clay limits houses without basements on under 1%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 377 flood losses here since 2016, 48% of them in buildings with basements. 45% of homes were built before 1980, against 50% nationally; the median home dates from 1983.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Chester County
| Expansive clay (limits slab homes) | under 0.1% |
| High water table (limits basements) | 20.9% |
| Septic fields very limited | 77.2% |
| Clay swell (LEP, by area) | 1.9% |
| High-swell land (LEP 6%+) | 0.1% |
| Urban land, not rated | 9.0% |
| Mapped soil | 486,047 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Glenelg | 16% | 0% |
| Gladstone | 16% | n/a |
| Manor | 11% | n/a |
| Edgemont | 5% | n/a |
| Penn | 4% | n/a |
| Glenville | 4% | n/a |
How we count · survey areas PA029 (2025-09-05)
What the numbers mean here
On 21% of Chester County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 40.55 in, 7.96 in below the 1991-2020 average year of 48.51 in.
USDA rates 77% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 45 of the last 52 weeks; the most was 100% of its area, in 17 weeks, most recently on the August 4, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 1% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
377 flood losses since 2016, $17.3 million paid. The worst year was 2021, with 215. Foundations of the buildings, where recorded: 48% basements, 27% slabs, 4% crawl spaces, 21% elevated. Median water depth outside the building: 22 in.
| Year | Flood losses |
|---|---|
| 2016 | 9 |
| 2017 | 0 |
| 2018 | 36 |
| 2019 | 20 |
| 2020 | 73 |
| 2021 | 215 |
| 2022 | 2 |
| 2023 | 7 |
| 2024 | 8 |
| 2025 | 3 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 48.51 in |
| 12 months to August 2026 | 40.55 in (-7.96) |
| 2025 | 40.84 in (-7.67) |
| Wettest year since 1895 | 2018: 70.33 in |
| Driest year since 1895 | 1930: 31.23 in |
| Days with 1 inch or more, normal at GLENMOORE (8 mi away) | 14.1 |
Homes
| Housing units | 212,491 |
| Median year built | 1983 |
| Built before 1980 | 45% |
| Built 2000 or later | 26% |
| Owner-occupied | 75% |
| Median value, owner-occupied | $485,600 |
| Single-family detached | 60% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Delaware County, PA | 19 mi | under 1% | 22% |
| Montgomery County, PA | 26 mi | under 1% | 44% |
| Lancaster County, PA | 27 mi | under 1% | 18% |
| New Castle County, DE | 28 mi | 2% | 34% |
| Cecil County, MD | 30 mi | 2% | 38% |
| Berks County, PA | 32 mi | 0% | 27% |
| Philadelphia County, PA | 33 mi | 0% | 5% |
| Salem County, NJ | 35 mi | 2% | 54% |
Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status