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Philadelphia County, Pennsylvania

USDA's soil survey flags shrink-swell clay on 0% of Philadelphia County's mapped land and a shallow water table under basements on 5%, both below the national shares of 15% and 29%. None of the county is in drought on the September 22, 2026 Drought Monitor map.

FEMA's flood data list 467 flood losses here since 2016, 27% of them in buildings with basements. 83% of homes were built before 1980, against 50% nationally; the median home dates from 1949.

Data as of September 22, 2026 · sources

0%

expansive clay: shrink-swell limits slab homes

5%

high water table: limits basements

0%

in drought, September 22, 2026

83%

of homes built before 1980

Soil under Philadelphia County

Expansive clay (limits slab homes)0.0%
High water table (limits basements)4.7%
Septic fields very limited13.4%
Clay swell (LEP, by area)1.7%
High-swell land (LEP 6%+)0.0%
Urban land, not rated67.3%
Mapped soil91,200 acres
Soil seriesShare hereSeries nationally: expansive clay
Chester10%n/a
Manor4%n/a
Howell2%n/a
Hatboro1%n/a
Duncannon1%n/a
Marshunder 1%n/a
Delaware County: 0%Camden County: 0%Montgomery County: 0%Gloucester County: 2%Bucks County: 0%Burlington County: 1%Mercer County: 0%Salem County: 2%Philadelphia County DelawareCamdenMontgomeryGloucesterBucksBurlingtonMercerSalemPhiladelphia
Philadelphia County (heavy outline) and nearby counties, shaded by expansive clay share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas PA101 (2025-09-04)

What the numbers mean here

Rain over the 12 months to August 2026: 37.89 in, 9.04 in below the 1991-2020 average year of 46.93 in.

With shrink-swell clay on 0% and a shallow water table on 5% of the land, the soil survey points to neither problem across most of Philadelphia County; conditions still vary lot by lot.

Drought

0% of the county is in drought (D1 or worse) on the September 22, 2026 map. Part of the county was in drought in 39 of the last 52 weeks; the most was 100% of its area, in 13 weeks, most recently on the July 7, 2026 map.

September 30, 2025Share of area in drought, weeklySeptember 22, 2026
Category, September 22, 2026Share of county
D0 abnormally dry or worse0%
D1 moderate drought or worse0%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

467 flood losses since 2016, $27.3 million paid. The worst year was 2020, with 251. Foundations of the buildings, where recorded: 27% basements, 36% slabs, 2% crawl spaces, 36% elevated. Median water depth outside the building: 33 in.

YearFlood losses
201612
20172
201819
201912
2020251
2021142
20223
202311
20244
20256
2026 to date5

Rain

Average year, 1991-202046.93 in
12 months to August 202637.89 in (-9.04)
202536.88 in (-10.05)
Wettest year since 18952018: 66.09 in
Driest year since 18951965: 30.80 in
Days with 1 inch or more, normal at PENNSAUKEN 1N (7 mi away)13.6

Homes

Housing units748,270
Median year built1949
Built before 198083%
Built 2000 or later10%
Owner-occupied52%
Median value, owner-occupied$243,100
Single-family detached9%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Foundation repair, US $2,200 to $8,200 Fixr, January 27, 2026
Pier-and-beam repair, US $2,000 to $15,000 Fixr, January 27, 2026
Foundation inspection, US $300 to $600 Fixr, January 31, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Delaware County, PA 15 mi under 1% 22%
Camden County, NJ 17 mi under 1% 44%
Montgomery County, PA 19 mi under 1% 44%
Gloucester County, NJ 20 mi 2% 34%
Bucks County, PA 23 mi under 1% 52%
Burlington County, NJ 27 mi 1% 61%
Mercer County, NJ 30 mi 0% 44%
Salem County, NJ 32 mi 2% 54%

Sources: USDA SSURGO (September 4, 2025) · US Drought Monitor (September 22, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status