Tennessee / Crockett County
Score 51 · elevated · #3 of 88 in TN
Crawl space moisture in Crockett County, TN
65% of Crockett 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 — 95% of acres — it averages 1.7 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.7 ft
- 2Wet soils 21%
- 3Moisture score 51
- 4EPA radon zone 3
Reading the Crockett County soil survey
The score of 51 combines four parts, each from the USDA survey: wet drainage classes contribute 40.8 points of 100 on their own scale, group D soils 56.9, a shallow water table 70.1, and flooding 24.7; the weights are on the methodology page. The dominant hydrologic group is D (36% of acres): very slow infiltration, high runoff (clays, high water table).
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 Crockett County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Crockett County against the rest of Tennessee
Crockett County ranks 3 of 88 Tennessee counties, 39 points above the state median of 12. Only 2 other counties in the state score higher. Statewide, 9% of mapped soil is in the wet drainage classes; here it is 21%, half again the state figure or more. After moderately well drained, the next most common class is somewhat poorly drained at 13%.
Flooding. 8.5% of acres with a flooding class are rated frequent; 27% 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 3. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near Crockett County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area TN033; drainage covers 100% of 170,250 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.