# What Causes Foundation Settlement in Tennessee?

> Why foundations settle in Tennessee: karst and sinkholes, thin soil over limestone, clay moisture swings, poorly compacted fill, and water. Plus sinkhole insurance.

URL: https://tennesseefoundationrepair.us/guides/what-causes-foundation-settlement/

**Short answer:** Foundations settle when the soil under them compresses, shrinks, washes out, or gives way. In Tennessee the usual causes are poorly compacted fill, clay soil drying and shrinking, water softening or eroding soil, and karst: limestone and dolomite that dissolve into voids and sinkholes under about 43.5% of the state, according to the USGS.

Every house settles a little as its weight presses into the ground. The trouble starts when one part settles more than another, called differential settlement. That is what cracks walls, tilts floors, and jams doors. The cause is almost always in the soil, and in Tennessee the soil sits on some unusual rock.

## The common causes

**Poorly compacted fill.** Building lots are graded, and soil moved to fill low spots compresses over time if it was not compacted well. Fill on the downhill side of a hillside lot, or over a filled sinkhole, is a classic setup for a settling corner.

**Clay that shrinks and swells.** Clay soils take on water and expand, then dry and shrink. Long dry spells can pull soil away from footings, and tree roots near the house can dry the soil further.

**Water.** Roof runoff dumped at the foundation, ground that slopes toward the house, and leaking pipes soften soil and can carry fine particles away. Water is also what drives karst.

**Karst and sinkholes.** About 43.5% of Tennessee sits on karst or rock that can form it, according to the U.S. Geological Survey. Limestone and dolomite dissolve slowly, leaving voids. Soil above can slowly ravel into those voids or, less often, collapse suddenly.

**Inadequate footings.** Porches, additions, and older houses sometimes sit on footings that were too small or too shallow for what they carry.

## How Tennessee's regions differ

A 1997 USGS study compared Tennessee's karst regions using thousands of well records. Two of its findings matter for homeowners:

| Region | Cities | Median depth to bedrock | Area in 1%+ sinkhole zones |
|---|---|---|---|
| Inner Central Basin | [Nashville](/foundation-repair-nashville-tn/), [Murfreesboro](/foundation-repair-murfreesboro-tn/) | about 2.4 m (~8 ft) | about 50% |
| Valley and Ridge | [Knoxville](/foundation-repair-knoxville-tn/), [Johnson City](/foundation-repair-johnson-city-tn/), [Kingsport](/foundation-repair-kingsport-tn/), [Chattanooga](/foundation-repair-chattanooga-tn/) | about 12.8 m (~42 ft) | about 38% |

Source: [USGS WRIR 97-4097, Table 4](https://pubs.usgs.gov/wri/wri974097/datatab/table4.html). Medians hide wide local variation.

In the Central Basin, thin soil over rock means a footing can bear partly on rock and partly on soil, which settle differently. In the Valley and Ridge, deeper and more variable soil over karst means settlement can come from soil movement or from voids well below the surface, and foundation piers may need to go much deeper.

Local rules reflect this. [Knox County's stormwater management manual](https://knoxcounty.org/stormwater/manual/Volume%202/Volume2Combined.pdf) requires geotechnical studies for structures within 50 feet of a sinkhole's rim and flags fill placed in or near sinkholes as an added settlement hazard. In Murfreesboro, a [USGS study of 78 sinkholes](https://pubs.usgs.gov/sir/2005/5281) found that changes to the land surface affect how sinkholes flood.

## Signs that settlement is happening

- Diagonal cracks from the corners of doors and windows.
- Stair-step cracks in block or brick.
- Floors sloping toward one side or corner.
- Doors and windows that stick or swing on their own.
- A porch, chimney, or addition pulling away from the house.

These are symptoms, not proof. Seasonal humidity, framing shrinkage, and settling finishes cause some of them too. See [are foundation cracks serious?](/guides/are-foundation-cracks-serious/)

## What you can control

You can't change the rock, but you can control a lot of the water. Keep gutters clear, extend downspouts well away from the foundation, make sure the ground slopes away from the house, fix leaking pipes, and don't direct runoff toward a sinkhole. These steps won't fix a house that has already moved, but they help keep it from getting worse.

Don't try to jack up, shim, or support a settling house yourself. Lifting a structure without knowing the cause can crack more than it fixes.

## Sinkholes and insurance

Tennessee law (T.C.A. § 56-7-130) requires insurers that sell homeowners coverage to offer sinkhole loss coverage. It is optional, usually costs extra, and can be added after a policy starts, according to the [Tennessee Department of Commerce and Insurance](https://www.tennessee.gov/content/dam/tn/commerce/documents/insurance/bulletins/081215_Sinkhole_Coverage_for_Residential_Properties_Bulletin.pdf). Ordinary settlement is commonly excluded from standard policies.

## How settlement gets repaired

The usual fix is stabilization: [foundation piers](/foundation-pier-installation/) that carry the settling section down to firmer ground, sometimes with a partial lift. Slabs may be raised with mudjacking or foam, and drainage is usually part of a lasting fix. Where a sinkhole is involved, a geotechnical or structural engineer may need to assess the ground first. See [foundation settlement repair and stabilization](/foundation-settlement-repair/).

## Quick answers

**Is some foundation settlement normal?**

A small amount of even settlement as a new house loads its soil is common and often harmless. Problems come from differential settlement, where one part moves more than another, which cracks walls and slopes floors.

**Can a sinkhole damage my foundation?**

It can. Knox County's stormwater manual, for example, calls sinkhole areas unstable for construction and warns that structures on soil in them can settle or collapse. If a depression opens near your house, keep people away and get it evaluated.

**Does homeowners insurance cover foundation settlement in Tennessee?**

Ordinary settling is commonly excluded. Tennessee requires insurers to offer optional sinkhole coverage, usually at extra cost. Read your policy and ask your agent before assuming either way.

Referral disclosure: Tennessee Foundation Repair is an independent contractor-referral service. We help connect Tennessee property owners with participating foundation repair professionals. Services are performed by independent contractors. We may receive compensation for qualified referrals. Phone: (865) 276-7293.