S.C. Code Ann. § 4-25-210

It shall be unlawful for any person to erect or construct any improvements on real estate, which cost in excess of one thousand dollars, in any county containing a municipality with a population of more than ninety-seven thousand, according to the latest official United States census, unless an application has been filed with and a permit granted by the county auditor to erect or construct such improvements; provided, that no application or permit shall be required for such improvements upon real estate situate within any incorporated municipality, which requires a permit for the erection or construction of such improvements.