Charleston, SC Accessory Structures: ADU Rules (2026)

Section 54-214 of the Charleston Zoning Ordinance governs accessory dwelling units citywide. Before building one, an owner submits a scaled site plan and a signed statement certifying no covenant bars an ADU on the lot to the Department of Planning and Preservation, along with a draft Declaration of Covenants and Restrictions (DCR) that Planning and the Office of Corporation Counsel must approve. The DCR has to be recorded with the Register of Deeds, and the city will not issue a certificate of occupancy for the ADU until the applicant produces the recorded, approved copy.

Only one ADU is allowed per lot, and the ADU cannot push the property past two total dwelling units. Conditioned floor area tops out at 850 square feet; that ceiling drops to a 600-square-foot building footprint when the ADU occupies an accessory building relying on the Sec. f setback exception to sit closer to a property line than the standard yard rules allow. The ADU may carry its own electric, gas and water meters separate from the principal home. One additional off-street parking space has to be provided for the ADU on the lot, on top of whatever parking the existing uses already require; that new space can sit in tandem behind another required space rather than needing its own driveway apron.

The recorded DCR also locks in the terms found in Sec. 54-214(g), covering owner-occupancy, subleasing, income-restricted rent when the unit received a city subsidy, a two-adult occupancy cap, and a ban on converting the property into a horizontal property regime.