Charleston County, SC Accessory Structures: ADU Rules (2026)
ADU rules in Charleston County, SC, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs per lot
- One
- Rural max size
- 1,500 sq ft heated
- Rural lot bonus
- 50% larger than minimum
- Setbacks
- Full district standards apply
- Separate meter (attached)
- Not allowed
Summary
In unincorporated Charleston County, one accessory dwelling unit is allowed per lot in Agricultural and Residential districts. In the Rural Area the ADU cannot exceed 1,500 square feet of heated floor area, and it must meet all normal district setbacks.
In Agricultural and Residential Zoning Districts, one Accessory Dwelling Unit may be established on an existing Lot subject to the following standards: A. If located in the Rural Area, the Lot must have a minimum area at least 50 percent larger than the minimum area required for a Principal Structure and the heated gross floor area of the Accessory Dwelling Unit shall not exceed 1,500 square feet. B. Only one Accessory Dwelling Unit shall be permitted per Lot.
Full Breakdown
The Charleston County Zoning and Land Development Regulations (ZLDR) Sec. 6.5.9 govern ADUs on unincorporated county land. Only one ADU is permitted per lot. In the Rural Area the lot must be at least 50 percent larger than the minimum required for a principal structure, and the ADU's heated gross floor area may not exceed 1,500 square feet. ADUs must comply with all district setback, buffer, coverage, height and waterfront standards. Lots that contain or abut an OCRM Critical Line must also meet Article 4.24.2 minimum-lot standards. Separate electrical meters are not allowed for attached ADUs. Inside Charleston city, Mount Pleasant or other municipalities, that town's own ADU code applies instead.
Violations & Fines
ADUs built without required zoning permits or exceeding size/setback standards are zoning violations enforced under ZLDR Chapter 11 (Violations, Penalties, and Enforcement) by the Zoning and Planning Department.
Frequently Asked Questions
Can I put a second ADU on my lot?
Do these rules apply inside Charleston city?
Sources & Official References
Other rules in Charleston County
How Charleston County compares: Easiest Cities to Build an ADU·Compare Charleston County to another location·View the South Carolina accessory structures overview
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