Crawl space moisture in Washington County, PA

82% of Washington County's soil falls in hydrologic group D or a dual D group: clays and high water tables that shed water slowly. Where a seasonal water table is reported — 82% of acres — it averages 2.4 ft below grade.

Size venting or encapsulation

1Water table 2.4 ft
2Wet soils 6%
3Moisture score 44
4EPA radon zone 2

Share of mapped soil acres in Washington County, PA by NRCS drainage class (dominant condition), bars to scale; wetter classes highlighted. Covers 98% of mapped acres.

Dominant drainage

Moderately well drained

67% of acres

Group D soils

82%

slow infiltration

Flood-prone acres

any flooding frequency

Ponding

acres where water ponds

Reading the Washington County soil survey

The score of 44 combines four parts, each from the USDA survey: wet drainage classes contribute 27 points of 100 on their own scale, group D soils 76.3, a shallow water table 52.3, and flooding 5.9; the weights are on the methodology page. The dominant hydrologic group is D (65% of acres): very slow infiltration, high runoff (clays, high water table).

Hydrologic soil groups in Washington County by share of acres, columns to scale. Group D and dual groups (x/D) shed water slowly and hold it near the surface.

At 2.4 ft the seasonal water table is usually below a crawl-space floor, but the 82% of acres that report one are by definition the wettest parts of the county; on those lots, a wet spring can bring water close to the footings.

Washington County against the rest of Pennsylvania

Washington County ranks 10 of 67 Pennsylvania counties, 19 points above the state median of 25. That puts it in the wettest quarter of the state. Statewide, 16% of mapped soil is in the wet drainage classes; here it is 6%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After moderately well drained, the next most common class is well drained at 20%.

Flooding. 5.5% of acres with a flooding class are rated frequent; 0.7% of acres with a flooding class are rated occasional. Flood-prone soils are a minority here, concentrated along streams; the score mostly reflects what happens between floods.

What it means for a crawl space here

In an elevated county the soil supplies more moisture than average, but a vented crawl space can work if the ground is covered: the code lets vent area drop from 1 sq ft per 150 to 1 per 1500 with a Class I vapor retarder on the ground, which is an admission of how much moisture comes from below. Grading, gutters and a ground cover usually decide whether a crawl space here stays dry before any decision about sealing it.

Radon. EPA radon zone 2. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.

Near Washington County by score

Warren County 43 Lawrence County 46 Susquehanna County 46 Venango County 46

All 67 Pennsylvania counties

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area PA125; drainage covers 98% of 551,441 mapped acres); EPA Map of Radon Zones, county table (June 2024 JSON); IRC R408.3 Unvented crawl space, as adopted in S.C. Code Regs. 8-1221 (LII). Checked 2026-10-23.