City · Utah
ADU rules in Millcreek
These are the primary sources for accessory dwelling unit regulations in Millcreek: the city's own zoning code, planning department pages, and permit guides. Start here before talking to anyone: the rules below are what your permit reviewer will apply.
Rules at a glance
Permitted use in R-1 and A zones subject to chapter design standards; requires min 8,000 SF lot, rear-yard location, permanent structure (no trailers/portable structures)
MKZ 18.71.040, 18.71.090, Table 18.71-2Internal ADUs are a permitted use as set forth in Utah Code 10-9a-530; attached ADUs are permitted uses in R-1 and A zones subject to design standards (entrance not visible from public right-of-way)
MKZ 18.71.040, 18.71.070, 18.71.080Detached ADU gross square footage is the lesser of the gross square footage of the existing main building or 1,000 SF (Table 18.71-2, as amended by Ord. 25-38, 9/8/2025); no explicit cap for internal/attached, but lot coverage of the underlying zone applies
MKZ 18.71.090 Table 18.71-2Property eligible only if owner occupied; city records a notice at the Salt Lake County Recorder stating the property is owner-occupied and the ADU may only be used per city land use regulations
MKZ 18.71.030, 18.71.050City FAQ: all ADUs require at least one off-street parking stall and no ADU parking is allowed on the street; garage conversions need one additional ADU space plus at least one covered replacement stall; parking standard stated on official city ADU page, not within chapter 18.71 itself
City ADU FAQ (millcreekut.gov); parking standards referenced in MKZ 18.71.130Internal, attached, and detached ADUs are permitted uses in R-1/A (no conditional use permit), but new detached ADUs require a site plan review application with Planning & Zoning plus an ADU application/affidavit, and conversions of legally nonconforming structures require a Land Use Hearing Officer permit
MKZ 18.71.040, 18.71.130Code: a detached ADU shall not be used as a short-term rental (violations curable within 14 days, subject to lien up to $100/day per 18.71.120). City FAQ: internal and attached ADUs may operate short-term rentals with an ADU application and Millcreek business license; long-term rentals (30+ days) allowed in all ADU types with an ADU compliance letter and business license
MKZ 18.71.090; City ADU FAQThe fine print: 8 caveats that can change the picture
- ADUs are allowed only in R-1 (single-family residential) and A (agriculture) zones on single-household properties; one ADU maximum per property
- Detached ADUs require a lot of at least 8,000 sq ft and must be located in the rear yard; internal and attached ADUs have no minimum lot size
- The 1,000 sq ft detached cap is actually the lesser of the main building's gross square footage or 1,000 sq ft, and lot coverage limits of the underlying zone can further reduce allowable size
- Occupancy of an attached or detached ADU is limited to 2 adults plus any number of children
- ADUs cannot be sold separately or subdivided from the principal dwelling, and separate utility meters are prohibited
- Detached ADU height is the lesser of 24 ft or the main building's height, with an extra inch of side/rear setback per inch of height over 16 ft 6 in
- The curated code link to Chapter 19.89 is stale: Millcreek recodified its zoning code, and ADU standards now live in Title 18 as MKZ 18.71 (Repealed and Reenacted by Ord. 25-12 on 4/28/2025; Table 18.71-2 amended by Ord. 25-38 on 9/8/2025); the city's own page links to 18.71
- The curated FAQ PDF (DocumentCenter/View/956) is a pre-ordinance public engagement packet that predates adoption and describes proposals (e.g. 2 parking spaces, conditional use for detached) that differ from the adopted ordinance; it should not be used as a source of current rules
Summarized from Millcreek's ordinance text, read July 2026; every row links the code section it came from. Rules often vary by zone and lot, so treat this as orientation, not a permit determination, and confirm with the planning department before you commit to a design.
ADU regulations
- millcreekut.govOfficial sourceVerified July 2026https://www.millcreekut.gov/341/Accessory-Dwelling-Units-ADUs
- millcreek.municipalcodeonline.comOfficial sourceVerified July 2026Municipal Code §18.71 ACCESSORY DWELLING UNIT STANDARDShttps://millcreek.municipalcodeonline.com/book?type=planzone#name=18.71_ACCESSORY_DWELLING_UNIT_STANDARDS
Utah statewide law also applies
Utah sets baseline ADU rights at the state level. Where local rules are stricter than state law allows, state law usually wins, so both are worth reading.
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