The short answer: the Mecklenburg County soil survey describes a patchwork. Its largest unit, Cecil, covers 41% of the county and is rated moderate in the older county survey but low in USDA’s current series description. Higher-rated soils exist in the county, but they are concentrated in specific areas, not everywhere. That is why this site does not say “Charlotte has expansive soil.” It depends on the lot.
How to read a soil map
A soil survey groups ground into general map units, each a pattern of named soils. A “shrink-swell” rating describes how much a soil’s clay changes in volume as it wets and dries. The survey also gives a rating for suitability for urban uses, which folds in shrink-swell, wetness and how slowly water moves through. None of this is a verdict on a house. It tells you what to look at.
The ratings table
| Soil | County survey rating | USDA series description | Where it appears |
|---|---|---|---|
| Iredell | Very high | Vertic subgroup, with a linear-extensibility measure, no class given | Mainly south-central and southwest county, some NE and NW |
| Enon | High | High | Wilkes-Enon unit, scattered across the county; also the northern Enon-Helena-Vance unit |
| Helena | High | High | Enon-Helena-Vance unit, north county including Huntersville |
| Wilkes | Moderate | High | Wilkes-Enon unit |
| Mecklenburg | Moderate | Moderate | Iredell-Mecklenburg unit |
| Cecil | Moderate | Low | Largest unit, most of the county |
| Georgeville | Low | Low | Slate belt, eastern tip |
| Goldston | Low | n/a | Slate belt, eastern tip |
Reading across: the Iredell-Mecklenburg unit covers about 11% of the county, formed from diorite, gabbro and other iron and magnesium-rich rock. The survey rates its major soils as Low potential for urban uses for most urban uses, because of the very high shrink-swell rating, wetness and slow permeability. The Wilkes-Enon unit is 13% of the county, scattered through the county. The slate-belt unit of Georgeville, Goldston and Lignum is 2% of the county, in the eastern tip.
The Cecil conflict, stated plainly
The sources disagree about Cecil. The older county survey rates Cecil sandy clay loam moderate for shrink-swell. USDA’s current series description rates it low. We cannot tell you which is right for a given lot, and both ratings are published by public agencies. The same split appears for Wilkes, rated moderate in the county survey and high in the current description. Treat this as a reason to avoid a one-word answer, not as something to fix with a guess.
What the soil does and does not tell you
- It tells you where to look. A house on a unit with higher-rated soil deserves closer attention to drainage and gutters.
- It does not tell you why a house moved. Roof water at the wall, a leaking pipe, tree roots, poor fill and an undersized footing all cause movement on any soil.
- It does not stop at the lot line. Mapped units contain inclusions of other soils.
For town detail, the Huntersville page covers the Enon-Helena-Vance unit, the Mint Hill page covers the slate-belt edge and the Matthews page explains why no single series is claimed there. The NC Geological Survey adds that a geotechnical engineer can identify expansive soils, with fixes such as moisture barriers, special foundation designs or soil replacement.
Before you sign
- Ask the contractor to say what they think is causing the movement, and what they saw that makes them say so.
- Be cautious of a quote that blames “Charlotte clay” without looking at your lot’s water.
- If the price is large, consider an independent opinion, covered in the inspection and engineer guide.
Want a contractor to look at it? Call to schedule an inspection.