ADU laws in South Dakota

In plain words

South Dakota does not have a statewide ADU law. An accessory dwelling unit (ADU) is a small second home on the same lot as a house. It could be a basement apartment, an addition, or a backyard cottage. In South Dakota, each city or county decides whether ADUs are allowed. They do this through zoning, which means the local rules about what you can build where. No ADU bill has come before the Legislature from 2023 through 2026, and none is pending now. The two biggest cities do allow ADUs, with limits. In both Sioux Falls and Rapid City, the owner must live on the property. This is called an owner-occupancy rule. Both cities also require extra off-street parking. Rapid City makes you register the ADU with the city. It also bans detached ADUs on smaller lots. Sioux Falls keeps detached ADUs in the backyard and limits their size. Rules in smaller towns and rural counties vary. Some areas have very little zoning at all. Building codes and septic rules still apply there. Before you plan, call your local zoning office. You may be able to build an ADU if your local rules and your property allow it.

The rules at a glance

What to do next

1. Find out who handles zoning for your address: your city's planning office if you are inside city limits, or the county planning and zoning office if you are not.
2. Ask whether ADUs are allowed in your zone, whether the owner must live on site, and how many parking spaces you need.
3. In Rapid City, plan to register the ADU with the Community Development Department as part of the permit process.
4. Check lot size, setback (how far a building must sit from property lines) and size limits before you design.
5. Check your deed and any HOA or subdivision covenants, which can ban a second unit even where zoning allows one.
6. If you are not on city sewer, confirm with the county or state whether your septic system can handle a second unit.

What your town still decides

South Dakota has no state law about ADUs. State statutes say cities (SDCL 11-4-1) and counties (SDCL 11-2-13) 'may' adopt zoning, so zoning itself is optional, and each place that zones decides whether to allow a second unit on a house lot. Some small towns and rural areas may have little or no zoning, while the two largest cities have written ADU rules. Sioux Falls and Rapid City both require the owner to live on the property and require extra off-street parking. Outside city limits near Sioux Falls, a joint city-county zoning area has its own ADU section. A search of every bill title from the 2023 through 2026 regular sessions, plus the September 2025 special session (two prison bills), found no bill about accessory dwelling units. The 2026 session did pass SB 3, which stops local governments from requiring building permits for like-for-like repairs such as siding, gutters and same-size windows on owner-occupied houses, but it does not touch ADUs. The Legislature meets each January; the next session starts in January 2027.

Examples of local rules

• Sioux Falls: Detached ADUs are a 'permitted special' accessory use in the city's single-family building forms, which means they are allowed if they meet set standards; an owner who cannot meet a standard can seek a conditional use permit instead. Only one extra unit is allowed and one of the two units must be owner-occupied. At least two off-street parking spaces are required (existing spaces count). A detached ADU can be no more than 40% of the main home's square footage, must sit in the rear yard at least 10 feet from the house, and must meet the same yard rules as the house. These sections were last amended by Ord. 34-26 on May 5, 2026. Source
• Rapid City: Code section 17.50.219 (last amended by Ord. 6714 in 2026) allows one ADU per owner-occupied single-family home in the LDR-1, LDR-2, MDR, HDR and General Agricultural districts (inside the house only in Park Forest). The owner must live full time in the house or the ADU. Detached units are not allowed in front yards or on lots under 6,500 sq ft, must be smaller than the house's footprint, and may cover no more than 10% of the lot. Three off-street parking spaces are required in total. Every ADU must be registered with Community Development; staff approve registrations that meet the rules, and any deviation needs a variance. Source
• Sioux Falls / Minnehaha County joint extraterritorial area: In the zoning area just outside Sioux Falls city limits, Sec. 159.305 (Ord. 18-25, passed April 22, 2025) allows one ADU per parcel where zoning allows it, on permanent frost footings, with two extra off-street parking spaces and proof of wastewater capacity before a conditional use permit is approved. Attached ADUs can be up to 75% of the home's finished floor area and detached ADUs up to 50%, or up to 100% when a house more than 30 years old is reused as the ADU. Detached units in the rear yard must be at least 7 feet from side and rear lines and 10 feet from other buildings. Source

What we’re still confirming

• Whether Sioux Falls applies the same rules to attached and inside ADUs as to detached ones isn't confirmed; ask the city.

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.