South Dakota state law: accessory dwelling unit (ADU) rules

South Dakota is a Dillon's-Rule state with a constitutional home-rule option under SDCL Chapter 6-12. The South Dakota Legislature has NOT enacted any statewide ADU-permissibility, by-right-ADU, or single-family-zoning-reform statute. ADU permissibility is therefore determined entirely by the underlying local zoning code. Statutory (non-home-rule) cities derive zoning authority from SDCL Chapter 11-4 (Municipal Zoning); the three home-rule cities (Sioux Falls, Rapid City, Watertown) operate under SDCL 6-12 charters with broader implied powers. Counties zone unincorporated areas under SDCL Chapter 11-2. Rapid City adopted ADU zoning provisions in December 2019 allowing detached ADUs in many residential zones. Sioux Falls permits ADUs as a permitted accessory use under Title 153 of the Sioux Falls Code of Ordinances. Most other South Dakota cities and towns do NOT have explicit ADU zoning provisions and may treat a proposed ADU as a non-conforming use requiring a special-use permit, conditional-use permit, or variance from the local Board of Adjustment under SDCL 11-4-21 (municipal) or SDCL 11-2-49 (county).

Constructing or occupying an ADU without compliance with local zoning produces local zoning-violation enforcement (stop-work orders, civil penalties, mandatory removal). State law (SDCL Chapter 11-4) authorizes municipalities to enforce zoning ordinances by injunction and civil penalty. No state-level penalty attaches to ADU non-compliance.