Salt Lake County, UT Building Setbacks & Zoning: Lot Coverage Limits (2026)

Salt Lake County does not give accessory dwelling units their own lot coverage percentage. Instead, Section 19.15.080 states that lot coverage maximums are set "as outlined per each zone," and that any addition to an existing building or construction of a detached ADU "shall not exceed the allowable lot or rear yard coverage standard for the underlying zone." In the county's R-1 single-family zones, where most ADUs are built, that underlying standard is Section 19.14.070's rule that no accessory building or group of accessory buildings may cover more than 25 percent of the rear yard, a cap that applies whether the structure is a shed, a detached garage, or a detached ADU.

Section 19.15.080 also cross-references Section 19.15.050, the ADU setback section: a detached ADU built after the 2021 adoption of Chapter 19.15 needs side yard setbacks matching the single-family dwelling standard for the zone, a minimum 10-foot rear setback, and at least 6 feet of separation from the main house, with an existing public utility easement wider than that setback controlling instead. Because setback and coverage rules interact, a lot too small or too narrow to satisfy both at once cannot legally hold a detached ADU at all: Section 19.15.030(B) is explicit that an ADU may not be permitted on any lot that cannot satisfy parking, setback, or lot coverage requirements.

A homeowner sizing a detached ADU therefore has to work backward from two numbers at once, the zone's rear-yard coverage percentage and its setback dimensions, before applying for the building permit that Section 19.15.110(A) requires.