Ohio / Brown County
Score 45 · elevated · #45 of 88 in OH
Crawl space moisture in Brown County, OH
58% of Brown 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 — 70% of acres — it averages 1.1 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.1 ft
- 2Wet soils 38%
- 3Moisture score 45
- 4EPA radon zone 2
Reading the Brown County soil survey
The score of 45 combines four parts, each from the USDA survey: wet drainage classes contribute 42.6 points of 100 on their own scale, group D soils 51.7, a shallow water table 57.3, and flooding 2.3; the weights are on the methodology page. The dominant hydrologic group is C/D (43% of acres): D when undrained, C when drained.
A water table under two feet is the single most important number here. A crawl-space floor is usually 18 to 36 inches below the joists and often below outside grade, so in a wet season groundwater can stand at or above the crawl-space floor across much of Brown County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Brown County against the rest of Ohio
Brown County ranks 45 of 88 Ohio counties, 1 points below the state median of 46. Wetter counties exist in Ohio, but the soil here still sits well above the national middle. Statewide, 44% of mapped soil is in the wet drainage classes; here it is 38%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After well drained, the next most common class is moderately well drained at 29%.
Flooding. 0.7% of acres with a flooding class are rated frequent; 2.7% 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 Brown County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area OH015; drainage covers 99% of 315,661 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.