ADU rules in Spearfish

Spearfish's zoning chapter (Chapter 156) has no accessory dwelling unit use or definition; a second home on a lot is handled district by district. In R-2 (one- and two-family) a lot may carry a 'maximum of two detached dwellings' by right, and R-3 takes every R-2 use. In R-1 (single-family) a 'second dwelling unit' needs a conditional use permit from the Planning Commission, and in the RLS-1 rural large-lot and AG districts a 'second residence/guest house' needs one too. So a backyard cottage is by right only in R-2 and R-3 and needs a public hearing in the single-family and rural districts.

An attached second unit is lawful by right as a 'two-family dwelling on one common lot' in R-2, and in R-3 (which allows every R-2 use). In R-1 the only route is the 'second dwelling unit' conditional use, a term the code never defines and does not limit to detached buildings, so an internal or attached unit there goes through a Planning Commission hearing. The code's 'dwelling unit' definition requires the unit to be served by municipal water and sanitary sewer.

Because Spearfish regulates second units as ordinary dwellings, no floor-area or percent-of-house cap exists. The district limits still govern: R-1 and R-2 cap lot coverage at 40% (R-3 at 30%), dwellings at 35 feet (R-1 also two and one-half stories) and detached accessory structures at 15 feet, with an 8,000 sq ft minimum lot. Whether the Zoning Administrator treats a detached R-1 second dwelling unit as a 35-foot dwelling or a 15-foot accessory structure is not stated in the code, and a CUP can add size conditions.

No section of Chapter 156 requires the owner to live on a property with a second dwelling, either at application or afterward; scoped full-text searches of the whole code for 'second dwelling', 'guest house' and 'accessory dwelling' return only the district use lists. South Dakota has no statute on ADU owner occupancy either way. A Planning Commission CUP could in principle add conditions, but none is written into the code.

The parking table requires 'two spaces per dwelling unit' for one-family and two-family dwellings, and the code has no ADU reduction, so a second unit adds two off-street spaces. In residential districts required spaces off local roads must sit at least 20 feet from the back of the sidewalk. A CUP is also reviewed for adequate parking and for 'unusual or unreasonable parking impacts'.

In R-2 and R-3 a second detached dwelling or a two-family dwelling is a primary permitted use needing only a building permit. In R-1 (second dwelling unit), RLS-1 and AG (second residence/guest house) it is a conditional use: the Planning Commission decides after a public hearing with mailed notice to owners within 140 feet and a posted sign, by simple majority of members present and voting. Applications go through the city's OpenGov portal.

Chapter 156 does not restrict who may rent a second dwelling, and the city's own Short-Term Rentals page says Spearfish 'does not currently regulate short-term rentals' (a taskforce and 2024 survey have studied the question). The zoning 'family' definition limits a dwelling unit to related persons or up to five unrelated people. A whole unit rented nightly or weekly for more than fourteen days a year without an owner or manager present is a state-licensed vacation home establishment (SDCL 34-18-1), with state sales and tourism taxes due.