Ohio / Fairfield County
Score 39 · moderate · #53 of 88 in OH
Crawl space moisture in Fairfield County, OH
54% of Fairfield 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 — 83% of acres — it averages 2 ft below grade.
- 1Water table 2 ft
- 2Wet soils 30%
- 3Moisture score 39
- 4EPA radon zone 1
Reading the Fairfield County soil survey
The score of 39 combines four parts, each from the USDA survey: wet drainage classes contribute 34.5 points of 100 on their own scale, group D soils 42.1, a shallow water table 57.7, and flooding 5.1; the weights are on the methodology page. The dominant hydrologic group is C/D (42% of acres): D when undrained, C when drained.
At 2 ft the seasonal water table is usually below a crawl-space floor, but the 83% 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.
Fairfield County against the rest of Ohio
Fairfield County ranks 53 of 88 Ohio counties, 7 points below the state median of 46. That places it in the middle range, nationally and for the state. Statewide, 44% of mapped soil is in the wet drainage classes; here it is 30%, 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 27%.
Flooding. 0.8% of acres with a flooding class are rated frequent; 6.5% of acres with a flooding class are rated occasional; 2% of acres with a flooding class are rated rare. 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 a moderate county the soil record is mixed rather than uniformly wet, so conditions vary from lot to lot. Where the lot drains, the model-code default — a vented crawl space with 1 sq ft of net vent per 150 sq ft of floor, or 1 per 1500 with a Class I vapor retarder on the ground — is a reasonable starting point; where the sections above point to a shallow water table or flood-prone soil on your lot, plan as for an elevated county. Either way, check the site first: grading that falls away from the foundation, gutters and downspouts that discharge well clear of it, and a ground cover over bare earth. A wet crawl space in a moderate county points to one of those first.
Radon. Fairfield County is in EPA radon zone 1, the highest predicted potential. A sealed crawl space and a radon system share most of their parts — the liner, the sealed seams, a fan — so if you are encapsulating, test for radon first and design both together. EPA itself says the zone map is not a reason to skip testing in zones 2 and 3.
Near Fairfield County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area OH045; drainage covers 96% of 325,357 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.