ADU rules in Watertown

Watertown's zoning ordinance (Title 21 of the Revised Ordinances) has no accessory dwelling unit, guest house or second-dwelling use, and it bars living space in accessory buildings outright: no accessory building may be used as a dwelling or contain cooking or sleeping facilities. Separately, 21.0303(1) allows only one residential building per zoning lot in every residential district, so a second freestanding house behind the first is not allowed either. The only routes to two separate residential buildings on one parcel are a Planned Unit Development rezoning or an apartment complex, which the ordinance lists only in the C-1 and C-3 commercial districts.

There is no ADU, accessory apartment or in-law suite use, and a single-family dwelling is defined as a home occupied by not more than one family. A second unit inside or attached to a house is possible only as a duplex, which is a permitted use in the R-2 and R-2A Single Family Attached districts and the R-3 Multi-Family district (21.1602, 21.1803, 21.2002), on a lot meeting the duplex minimums (R-2: 9,000 sq ft and 80 ft wide; R-3: 6,000 sq ft and 80 ft; R-2A: 6,000 sq ft and 50 ft). The A-1, R-1 and R-1C districts, which cover most single-family neighborhoods, allow single-family dwellings only, so a homeowner there would need a rezoning first.

Because Watertown has no ADU category, no ADU size limit exists. A duplex in R-2 needs 4,500 sq ft of lot per unit (9,000 sq ft lot, 80 ft wide); in R-3, 3,000 sq ft per unit (6,000 sq ft lot, 80 ft wide); in R-2A, 3,000 sq ft per unit (6,000 sq ft lot, 50 ft wide), each with a 35 ft height limit and the district setbacks. Accessory buildings (which may not hold living space) are capped cumulatively at 13 percent of lot area or 1,260 sq ft on lots up to 10,000 sq ft, with a 24 ft peak height.

Nothing in Title 21 requires the owner to live in either unit of a duplex, the only by-right way to create a second unit. Owner occupancy appears only for bed and breakfasts, which must be within an owner occupied principal dwelling. South Dakota has no statute on ADU owner occupancy.

The minimum parking table in 21.6302 lists 2 spaces per dwelling unit for single-family dwellings and 1 per bedroom for multi-family dwellings (defined as four or more units), but has no duplex row; under 21.6301(10) the Community Development Manager sets the requirement for unlisted uses, so the count for a duplex is a staff determination, most plausibly 2 per unit. The manager may also approve a reduction of up to 20 percent under 21.6301(9).

A duplex in R-2, R-2A or R-3 is a listed permitted use, so it needs only a building and zoning use permit issued by the Building Official under 21.0207(2) once the plans comply. No conditional use hearing is involved; the Board of Adjustment hears conditional uses (with published notice and mailed notice within 250 ft) under 21.0202, but no ADU or second-unit conditional use exists. Elsewhere a second unit requires a rezoning by the City Council.

Watertown has no rental registration or licensing ordinance and its zoning has no vacation-home or short-term rental use; the Title 21 definition of dwelling covers residential use 'either permanently or transiently'. Bed and breakfasts are a conditional use in R-1 (inherited by R-1C, R-2, R-2A and R-3), must be in an owner occupied home of at least 1,800 sq ft with no more than four guest rooms, and stays may not exceed 14 days in any 120-day period. A whole unit rented to the public by the day or week more than fourteen days a year is a vacation home establishment needing a South Dakota Department of Health lodging license (SDCL 34-18-1), and the city's 1 percent gross receipts tax on lodging rentals applies.