ADU Cost in South Carolina in 2026

ADU costs in South Carolina range from $65,000 for a basic garage conversion in Spartanburg to $345,000+ for a high-end Charleston historic district ADU. The most common Charleston build — a 600 sq ft mid-range ADU — costs $150,000 to $220,000. Greenville runs $115,000 to $175,000 for comparable projects. South Carolina labor costs run approximately 16% below the national average, making it one of the more affordable coastal ADU markets in the Southeast.

South Carolina's Coastal Area Management Act (CAMA) requires a state permit from the SC Department of Health and Environmental Control (SCDHEC) for construction within designated "critical areas" — typically within 1,000 feet of tidal waters, marshes, and beaches. CAMA applies to 20 South Carolina coastal counties including Charleston, Horry (Myrtle Beach), Beaufort (Hilton Head), and Colleton. CAMA review adds $2,000–$10,000 in fees and 60–90 days to project timelines. Check your specific parcel with SCDHEC before designing.

Charleston's Board of Architectural Review (BAR) oversees all new construction in the city's extensive historic districts — which cover much of the Charleston peninsula and adjoining neighborhoods. New ADUs in BAR-regulated areas must be compatible in scale, massing, materials, and architectural character with the surrounding historic context. The BAR meets monthly and reviews submitted design packages. Non-compliant plans are rejected and must be revised. Work with an architect familiar with Charleston historic preservation standards from the beginning of your design process.

No. South Carolina has no statewide ADU enabling legislation as of 2026. Each city and county sets its own ADU rules under local zoning authority. Charleston updated its code to allow ADUs in all base residential zones in 2020. Greenville permits ADUs in certain residential zones. Horry County has restrictions on full kitchens in accessory structures in some zones. Columbia/Richland County has a 500 sq ft hard cap in unincorporated areas. Always verify with your specific municipality before designing.

A mid-range 600 sq ft ADU in Charleston costs $160,000 to $220,000 all-in and generates $1,600 to $2,200 per month in rental income. Cash-on-cash ROI runs 9–11%, with a payback period of 11–14 years. Greenville offers better ROI (10–12%) due to lower build costs with comparable rent growth. Myrtle Beach STR income ($2,000–$3,500/mo peak season) can produce 12–15% ROI if Horry County's STR and kitchen rules permit the intended use.

Yes — for coastal South Carolina. The state building code requires wind load design for 130+ mph in coastal areas. Hurricane-rated windows, doors, roof connections, and fastening patterns are code requirements — not optional upgrades. This adds $8,000–$20,000 to ADU project costs in coastal zones. Inland markets (Greenville, Columbia, Spartanburg, Anderson) are in lower wind zones and do not face the full coastal hurricane construction premium.