ADU Cost in Utah in 2026

ADU costs in Utah range from $70,000 for a basic garage conversion in Cedar City to $402,000+ for a high-end detached unit in Park City. The most common Salt Lake City build — a 600 sq ft detached mid-range ADU — costs $160,000 to $230,000. Wasatch Front seismic engineering requirements (SDC D) add $6,000–$15,000 to detached projects. Impact fees ($4,500–$6,500 in SLC) are commonly overlooked in early budgets.

Utah Senate Bill 284 requires all Utah cities with a population of 5,000 or more to adopt ordinances permitting detached ADUs by October 2026. Cities that had previously banned detached ADUs outright must comply. The law requires a minimum lot size of 11,000 sq ft for detached ADU eligibility under the statewide mandate, though individual cities may permit ADUs on smaller lots under their own ordinances.

The Wasatch Front (Salt Lake, Utah, Davis, and Weber counties) sits on the Wasatch Fault — one of the most seismically active areas in the interior West. ADU construction in these counties requires Seismic Design Category D structural engineering. This includes lateral load analysis, reinforced framing connections, and hold-down hardware. It adds $6,000–$15,000 to detached ADU project costs. St. George and southern Utah are in lower seismic zones.

Yes. SB 284 and Utah's earlier ADU laws do not override private HOA CC&Rs. If your association's covenants prohibit detached structures, restrict accessory buildings, or require ARC approval, those rules remain enforceable. Utah's newer master-planned subdivisions (especially in Utah County and in Daybreak, Traverse Mountain, and similar communities) often have restrictive covenants. Review your CC&Rs before committing to any design or spending money on permits.

A mid-range 600 sq ft ADU in Salt Lake City costs $170,000 to $230,000 all-in and generates $1,400 to $1,900 per month in rental income. Cash-on-cash ROI runs 8–10%, with a payback period of 11–14 years. Park City ADUs offer higher rents ($1,800–$2,800) but also higher build costs, producing similar ROI. Utah's strong population growth and in-migration from California drive sustained rental demand across all major markets.

The Wasatch Fault is one of the most hazardous fault systems in the continental United States. A major Wasatch Fault rupture could be magnitude 7.0+ — comparable to the 1994 Northridge earthquake. Utah's building code reflects this with mandatory Seismic Design Category D requirements along the Wasatch Front. Every new structure — including ADUs — must be engineered for lateral seismic loads. This is enforced at permit review and cannot be waived.