Missouri / Ray County
Score 52 · elevated · #32 of 113 in MO
Crawl space moisture in Ray County, MO
67% of Ray 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 — 87% of acres — it averages 2 ft below grade.
- 1Water table 2 ft
- 2Wet soils 49%
- 3Moisture score 52
- 4EPA radon zone 2
Reading the Ray County soil survey
The score of 52 combines four parts, each from the USDA survey: wet drainage classes contribute 50.6 points of 100 on their own scale, group D soils 56.9, a shallow water table 60.7, and flooding 19.5; the weights are on the methodology page. The dominant hydrologic group is C/D (39% of acres): D when undrained, C when drained.
At 2 ft the seasonal water table is usually below a crawl-space floor, but the 87% 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.
Ray County against the rest of Missouri
Ray County ranks 32 of 113 Missouri counties, 13 points above the state median of 39. Wetter counties exist in Missouri, but the soil here still sits well above the national middle. Statewide, 32% of mapped soil is in the wet drainage classes; here it is 49%, half again the state figure or more. After moderately well drained, the next most common class is somewhat poorly drained at 35%.
Flooding. 1.2% of acres with a flooding class are rated frequent; 29.5% of acres with a flooding class are rated occasional; 3.2% of acres with a flooding class are rated rare. That is a large flood-prone share; a crawl space in the floodplain needs flood vents under most local floodplain ordinances, which is a separate rule from R408 and can rule out a fully sealed design.
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 Ray County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area MO177; drainage covers 100% of 367,174 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.