Expansive soils (shrink swell clays)

North Carolina has great diversity in rock types, this diversity in turn creates a greater diversity of soil types developed on the various rocks types.  Some soil, will expand (swell) when wet or shrink when drying.  A small amount of soil expansion can cause foundation damage. 

Expansive soils can occur in almost any location in the Mountains, Piedmont, and Coastal Plain of North Carolina. Some areas of the State tend to have an elevated occurrence of expansive soils due to the geology.  These areas include the Triassic basins and the Carolina terrane.

Triassic basin and Carolina terrane extents in NC

Map showing approximate extent of Triassic basins and Carolina terrane in North Carolina.

Expansive soils additional information:

http://www.dhses.ny.gov/oem/mitigation/documents/2014-shmp/Section-3-13-Land-Subs-Expansive-Soil.pdf

http://www.aegweb.org/?page=ExpansiveSoil

https://www.dmme.virginia.gov/dgmr/expansivesoils.shtml

Living with Unstable Ground: https://profile.usgs.gov/myscience/upload_folder/ci2011Aug0119050042954Unstable%20Ground%20Book%20final%20090407.pdf