Salt Lake County · 63,034 residents
Millcreek ADU rules
Millcreek: internal ADUs allowed; detached ADUs allowed (lot 8,000+ sq ft). Owner occupancy applies.
Internal ADU (inside the home)
Detached ADU (backyard building)
Not yet fully verified · last reviewed September 7, 2026 See sources
Millcreek ADU rules at a glance
| Rule | Internal ADU (basement, attic, inside the home) | Detached ADU (backyard building) |
|---|---|---|
| Allowed? | Allowed | Allowed |
| Minimum lot | Statewide statute includes a small-lot pathway around 6,000 sq ft for many internal ADUs — confirm how Millcreek applies it on your zone. | 8,000 sq ft. Minimum property area 8,000 sq ft (Table 18.71-2). |
| Owner occupancy | Property must be owner-occupied (18.71.030). | Owner-occupied property required (18.71.030). |
| Parking | Not specified in MKZ 18.71 table excerpt; check underlying parking chapter / staff. | Not listed in Table 18.71-2; confirm with Planning. |
| Zones | R-1 or A zone; single-household residential use (18.71.030–040). | R-1 and A zones as permitted use (with design standards). |
| Permit process | Compliance determination / notice of compliance may be recorded; business license to rent; building permit as needed. | ADU application with Planning & Zoning before building permit; site plan review for new detached ADU; one ADU per property (internal/attached OR detached). |
State law: detached ADUs from October 1, 2026
Millcreek is a “specified municipality” under Utah S.B. 284. Beginning October 1, 2026, it must permit one detached ADU as a permitted use on a lot of 11,000 sq ft or more that has a detached single-family home. The city can still apply setbacks, height, design, owner-occupancy and limited parking rules, and it may allow detached ADUs on smaller lots. How the state ADU laws work.
How our property map screens Millcreek lots
The map colors parcels using the rules on this page and the recorded lot size. A color is a planning screen, not a permit; Millcreek makes the decision.
- The statewide map screen starts a new external ADU at about 11,000 sq ft. Millcreek's researched external minimum is 8,000 sq ft. Lots below that city minimum stay highly unlikely on the map even when they clear 11,000 sq ft.
- "Likely" above 15,000 sq ft is this site's planning band for a large recorded lot. It is not a sentence in the Millcreek code. Owner occupancy, parking, setbacks, zones, and HOA rules below still have to be checked.
Planned communities, PRDs and PUDs
Reviewed on September 22, 2026 against this city's research file, its published ADU page where one was found, and Utah meeting packets. No adopted sentence was confirmed that allows or bans an ADU in every PUD, PRD, PRUD, or planned community. If the assessor class or subdivision name says PUD, PRD, PRUD, planned unit development, planned residential development, planned community, resort community, or master planned community, the map keeps that lot highly unlikely regardless of size. A plat, CC&Rs, or development agreement can still prohibit an ADU where the zone allows one.
Planning notes for Millcreek
Millcreek asks for the ADU planning application before a building-permit application. New detached units also need site-plan review. Prepare the letter of intent, owner affidavit, site plan and floor plan together; attached and detached designs need dimensioned elevations. Rental licensing is another step if you intend to lease the unit.
Bring these to your review
- Letter describing the intended ADU and occupants
- Site plan, floor plan and applicable elevations
- Owner information and proposed rental arrangement
The question to resolve first
Is the planning submission complete enough to move into building-permit review?
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Millcreek before you apply.
- Millcreek accessory dwelling units
Published city guidance covers internal, attached and detached applications
- Utah S.B. 284 (2026), enrolled bill
Statewide detached-ADU requirements for specified municipalities, operative October 1, 2026.
- Official Millcreek website
Common Millcreek ADU questions
Can you build an ADU in Millcreek?
Millcreek: internal ADUs allowed; detached ADUs allowed (lot 8,000+ sq ft). Owner occupancy applies. This is planning guidance, not a permit. Confirm the zone on your parcel with Millcreek.
What lot size does Millcreek require for an ADU?
Internal ADU: Statewide statute includes a small-lot pathway around 6,000 sq ft for many internal ADUs — confirm how Millcreek applies it on your zone. Detached ADU: 8,000 sq ft minimum. Minimum property area 8,000 sq ft (Table 18.71-2).
Does Millcreek require the owner to live on the property?
Internal ADU: Property must be owner-occupied (18.71.030). Detached ADU: Owner-occupied property required (18.71.030).
How much parking does a Millcreek ADU need?
Internal ADU: Not specified in MKZ 18.71 table excerpt; check underlying parking chapter / staff. Detached ADU: Not listed in Table 18.71-2; confirm with Planning.
What does it cost to build an ADU in Millcreek?
Wasatch Front planning bands are often about $55,000–$145,000 for an internal suite, $70,000–$175,000 for a garage conversion, and $95,000–$250,000 or more for a new detached unit, before unusual site work. These are planning ranges, not bids.
Can an HOA block an ADU in Millcreek?
City approval does not override CC&Rs or plat notes. Read the HOA documents and your subdivision plat before you design. A private restriction can stop a unit the city would otherwise allow.
Before you design: general checks for any Utah ADU
General planning advice, not Millcreek code.
- Confirm the zoning district on the city zoning map. The county assessor’s “residential” class is not zoning.
- Read your HOA CC&Rs and subdivision plat notes; private restrictions can block a unit the city allows.
- Sketch existing and proposed parking. Driveway geometry and access often decide what fits.
- Ask early about sewer, water and electrical capacity; utilities can force a redesign.
- Expanding a building’s footprint usually triggers full setback and height rules.
Nearby city ADU rules
Want to know what fits on your Millcreek lot?
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Utah ADU Builder provides educational planning guidance. This page is not legal advice and not a permit. Population: UGRC POPLASTESTIMATE / Census-derived municipal estimates (manual fill where UGRC blank). Editorial standards.