Mississippi / Clay County
Score 54 · elevated · #13 of 82 in MS
Crawl space moisture in Clay County, MS
59% of Clay County's mapped soil is somewhat poorly to very poorly drained, which means ground that stays wet near the surface for significant periods. Where a seasonal water table is reported — 87% of acres — it averages 2.3 ft below grade.
- 1Water table 2.3 ft
- 2Wet soils 59%
- 3Moisture score 54
- 4EPA radon zone 2
Reading the Clay County soil survey
The score of 54 combines four parts, each from the USDA survey: wet drainage classes contribute 50.5 points of 100 on their own scale, group D soils 68.8, a shallow water table 56.6, and flooding 21.5; the weights are on the methodology page. The dominant hydrologic group is D (51% of acres): very slow infiltration, high runoff (clays, high water table).
At 2.3 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.
Clay County against the rest of Mississippi
Clay County ranks 13 of 82 Mississippi counties, 19 points above the state median of 35. That puts it in the wettest quarter of the state. Statewide, 35% of mapped soil is in the wet drainage classes; here it is 59%, half again the state figure or more. After somewhat poorly drained, the next most common class is moderately well drained at 28%.
Flooding. 2.1% of acres with a flooding class are rated frequent; 32.3% of acres with a flooding class are rated occasional. 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 Clay County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area MS025; drainage covers 97% of 265,900 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.