Indiana / Franklin County
Score 32 · moderate · #71 of 92 in IN
Crawl space moisture in Franklin County, IN
52% of Franklin 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 — 54% of acres — it averages 1.5 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.5 ft
- 2Wet soils 20%
- 3Moisture score 32
- 4EPA radon zone 2
Reading the Franklin County soil survey
The score of 32 combines four parts, each from the USDA survey: wet drainage classes contribute 21.8 points of 100 on their own scale, group D soils 49.9, a shallow water table 41.8, and flooding 5.5; the weights are on the methodology page. The dominant hydrologic group is C (36% of acres): slow infiltration (clay layers).
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 on the soils that report a water table — about 54% of Franklin County's acres. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Franklin County against the rest of Indiana
Franklin County ranks 71 of 92 Indiana counties, 12 points below the state median of 44. That places it in the middle range, nationally and for the state. Statewide, 47% of mapped soil is in the wet drainage classes; here it is 20%, 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 20%.
Flooding. 1.9% of acres with a flooding class are rated frequent; 5.7% of acres with a flooding class are rated occasional; 0.9% 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. 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 Franklin County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area IN047; drainage covers 98% of 250,176 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.