Utah ADU Builder
Utah ADU answers · updated 2026-10-17
What is a specified municipality under Utah S.B. 284?
S.B. 284's detached-ADU rule applies only in specified municipalities: first- through fourth-class cities, and fifth-class cities of 5,000+ people in first-, second- or third-class counties. Which Utah cities qualify.
Short answer
It's the set of cities S.B. 284's detached-ADU rule applies to: every city of the first, second, third or fourth class, plus a fifth-class city with 5,000 or more people in a first-, second- or third-class county (Utah Code 10-21-101). Towns and unincorporated county land are not included.
Why it matters
Since October 1, 2026, Utah Code 10-21-304 requires each specified municipality to permit a detached ADU on any lot of 11,000 sq ft or larger that contains a single-family home, if the home is a permitted use there. Cities that aren't specified municipalities set their own detached-ADU rules.
City classes follow population (Utah Code 10-2-301): first class 100,000 or more; second 65,000 to 99,999; third 30,000 to 64,999; fourth 10,000 to 29,999; fifth 1,000 to 9,999. A city keeps its class until the Lieutenant Governor certifies a change based on the state's population figures (Utah Code 10-2-302 and 67-1a-2), so a city near a line can be classed differently than a recent estimate suggests. The table uses the latest population estimate on file for each city; where a city sits near 5,000 (Elk Ridge, for example), ask the city whether it treats itself as a specified municipality.
Specified municipalities on file (83)
Status as recorded in this site's city research.
Cities and towns on file that are not (19)
Their own codes decide whether and where detached ADUs are allowed.
| Place | County | City class |
|---|---|---|
| Coalville | Summit | 5 |
| Elk Ridge | Utah | 5 |
| Elwood | Box Elder | 5 |
| Emigration Canyon | Salt Lake | 5 |
| Erda | Tooele | 5 |
| Francis | Summit | 5 |
| Garland | Box Elder | 5 |
| Genola | Utah | 5 |
| Honeyville | Box Elder | 5 |
| Kamas | Summit | 5 |
| Lake Point | Tooele | 5 |
| Mantua | Box Elder | 5 |
| Marriott-Slaterville | Weber | 5 |
| Midway | Wasatch | 5 |
| Oakley | Summit | 5 |
| Uintah | Weber | 5 |
| Wendover | Tooele | 5 |
| Willard | Box Elder | 5 |
| Woodland Hills | Utah | 5 |
Sources
City rules come from this site’s dated research; each city page lists its official sources. This is planning information, not legal advice. How the property screen works.