House Settling in Tallahassee, FL

Why houses sink in Tallahassee

Two kinds of ground. Most of Tallahassee sits in the Red Hills, north of the Cody Escarpment. Soils there, like the Orangeburg series, have sandy clay under a sandy top layer. South of the escarpment, the Woodville Karst Plain has a thin layer of sand over limestone. Sandy soils like the Lakeland series drain fast. Each kind of ground moves in its own way, and a lot can change from one street to the next.

Heavy rain. Tallahassee gets close to 60 inches of rain in a normal year, the National Weather Service says. When a downspout dumps water at one corner for years, the soil under that corner gets soft or washes away. That corner sinks first.

Loose fill and buried debris. The Florida Geological Survey lists poorly packed soil, rotting stumps and buried trash among the things that make ground sink. On some lots, builders filled low spots or buried land-clearing debris. As it rots or packs down, the house above can drop.

Clay that dries out. The state also lists clay and organic layers that shrink as water leaves them. A long dry spell can pull the ground down under part of the house.

Age. Census survey data for the Leon County school district shows more than half of homes there were built between 1970 and 1999. Gutters, drains and old plumbing in homes that age often need work, and leaks under a slab soften the soil.

What the fix usually is

1. Measure. The inspector takes floor level readings across the house to see which part dropped and how far.
2. Find the water. Most sinking starts with water. Gutters, yard slope, plumbing leaks and drains all get checked.
3. Support the house. Piers go down under the sinking part to firm ground. In some cases the house can be lifted back closer to level.
4. Fix the water. Gutter extensions, a new slope or a French drain keep soil under the house from getting soaked.
5. Patch the cracks last, once the house is steady.

If the cause might be a sinkhole, testing by an engineer or geologist comes first.

Before the inspection

1. Mark each crack's ends with a pencil and the date.
2. Take photos with a coin or ruler for scale.
3. Check again after a heavy rain.
4. Find your house's age and whether it sits on a slab or a crawl space.
5. Gather papers on any past foundation work or claims.