Charleston, SC Accessory Structures: ADU Impact Fees (2026)

Under the South Carolina Development Impact Fee Act (SC Code §6-1-910 to §6-1-2010), a municipality may impose impact fees only after adopting a capital improvements plan, holding public hearings, and demonstrating a rational nexus between the fee and the cost of new public facilities. Charleston has not adopted a general transportation, parks, or school impact fee on residential ADUs. Charleston Water System charges water and sewer tap (impact) fees and capacity charges for new service connections; an ADU that uses the primary residence's existing water and sewer service may avoid a new tap fee, while an ADU requiring its own meter or upsized service will incur charges. Stormwater utility billing under Charleston's Stormwater Management Program may also apply. Standard zoning permit, building permit, and trade permit fees from the Charleston fee schedule apply at the time of building permit issuance. Fees are payable to the Charleston Permit Center. For properties in the Old & Historic District, additional BAR review fees apply.