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London, Ohio
Inside London's city limits, a shallow water table limits basements on 97% of mapped land, the highest of 6 cities in Madison County. Shrink-swell clay limits houses without basements on 36%, the 4th-highest of 6 cities in Madison County.
That water-table share is close to Madison County's 94%. FEMA's flood data list 6 flood losses since 2016 in ZIP code 43140 overlapping the city. Of its 4,970 homes, 56% were built before 1980; the median dates from 1974.
Data as of October 13, 2026 · sources · in Madison County
expansive clay: shrink-swell limits slab homes
high water table: limits basements
flood losses since 2016 in 1 overlapping ZIP
of homes built before 1980
Basement waterproofing in London
Basement waterproofing in London: a shallow water table limits basements on 97% of London's mapped land, more than in 89% of Ohio cities, and the ZIP code overlapping London logged 6 FEMA flood losses since 2016.
About 3,400 of London's 4,970 homes are detached houses.
Soil under London city limits
| Expansive clay (limits slab homes) | 35.6% |
| High water table (limits basements) | 97.3% |
| Septic fields very limited | 97.3% |
| Clay swell (LEP, by area) | 5.1% |
| High-swell land (LEP 6%+) | 20.1% |
| Mapped soil | 5,377 acres |
What the numbers mean here
Clay swell averages a linear extensibility of 5.1% by land area here, and 20% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 36% of the mapped land.
On 97% of London's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
USDA rates 97% of the land very limited for septic absorption fields.
Drought in Madison County
0% of Madison County is in drought (D1 or worse) on the October 13, 2026 map. County detail.
Flood losses by ZIP code
FEMA flood records since 2016 in the ZIP codes that overlap London. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 43140 | 100% | 6 | $93,737 |
Homes in London
| Housing units | 4,970 |
| Median year built | 1974 |
| Built before 1980 | 56% |
| Built 2000 or later | 18% |
| Owner-occupied | 64% |
| Median value, owner-occupied | $201,000 |
| Single-family detached | 68% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| West Jefferson | 7 mi | 38% | 93% |
| South Vienna | 10 mi | 30% | 69% |
| Midway | 11 mi | 10% | 97% |
| South Charleston | 12 mi | 11% | 63% |
| Catawba | 12 mi | 9% | 10% |
| Mechanicsburg | 14 mi | 3% | 82% |
| South Solon | 15 mi | 37% | 88% |
| Mount Sterling | 15 mi | 31% | 91% |
Sources: USDA SSURGO (August 5, 2026) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · Census ACS 2020-2024. Methods · Data status