South Carolina / Berkeley County
Score 58 · elevated · #9 of 46 in SC
Crawl space moisture in Berkeley County, SC
66% of Berkeley 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 — 88% of acres — it averages 1 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1 ft
- 2Wet soils 66%
- 3Moisture score 58
- 4EPA radon zone 3
Reading the Berkeley County soil survey
The score of 58 combines four parts, each from the USDA survey: wet drainage classes contribute 65 points of 100 on their own scale, group D soils 49.7, a shallow water table 75.2, and flooding 8.4; the weights are on the methodology page. The dominant hydrologic group is C/D (54% 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 Berkeley County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Berkeley County against the rest of South Carolina
Berkeley County ranks 9 of 46 South Carolina counties, 33 points above the state median of 25. That puts it in the wettest quarter of the state. Statewide, 34% of mapped soil is in the wet drainage classes; here it is 66%, half again the state figure or more. After poorly drained, the next most common class is somewhat poorly drained at 26%.
Flooding. 6.1% of acres with a flooding class are rated frequent; 0.2% 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 3. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near Berkeley County by score
All 46 South Carolina counties
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area SC015; drainage covers 88% of 787,300 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.