ADU rules in Park City

Detached Accessory Apartments are allowed, but only on lots of 3,750 sq ft or greater: "Detached Accessory Apartments are allowed on Lots 3,750 square feet or greater." They must meet the zoning district setbacks for single-family dwellings, comply with the Area of Disturbance, Limits of Disturbance and any stricter regulation shown on the recorded plat, and "shall not exceed a maximum height of eighteen feet (18') from Existing Grade." The 15-15-1 definition also lets an Accessory Apartment be created within a detached garage. Approval is a staff-level Administrative Permit, not a hearing. Two location carve-outs matter: detached Accessory Apartments are barred inside the Holiday Ranchettes Subdivision in the Single Family (SF) district, and Accessory Apartments of any form are prohibited in HRC and HCB storefront property along Main Street and the named cross streets. The other ADU path, the Internal Accessory Dwelling Unit under 15-4-7.1, is for units inside the house only.

Two attached paths exist. An Accessory Apartment is defined as "A self-contained Apartment, with cooking, sleeping, and sanitary facilities, created by adding on to or within a detached Single-Family Dwelling or detached garage," so an addition or an in-house conversion qualifies and no minimum lot size applies to the non-detached form. Separately, "One Internal Accessory Dwelling Unit may be constructed on a Lot that is 6,000 square feet or greater and contains one Single-Family Dwelling" under 15-4-7.1. Accessory Apartment is listed as an allowed use requiring an Administrative Permit in 18 of the 20 zoning districts whose use tables were read; Internal ADU is listed in the 11 residential districts (HRL, HR-1, HR-2, HRM, E-40, E, SF, R-1, RD, RDM, RM) and not in the commercial or industrial districts.

For Accessory Apartments the code says they "may be no more than one third (1/3) of the dwelling size, shall be limited to a maximum floor Area of 1,000 square feet and shall be no less than 280 square feet" and "shall have no more than two (2) Bedrooms." An Accessory Apartment also "may not increase the floor Area of a Structure over the maximum floor Area as specified in the Land Management Code or Subdivision approval," so the underlying zone or plat can bind before the 1,000 sq ft cap does. Section 15-4-7.1 sets no floor-area cap for Internal ADUs, only the 6,000 sq ft minimum lot size; Utah Code 10-21-303(1)(b)(i) bars a municipality from restricting the size of an internal ADU in relation to the primary dwelling.

It depends on which ADU type you build. For an Internal Accessory Dwelling Unit, "The Single-Family Dwelling shall be occupied by the Owner and the Internal Accessory Dwelling Unit shall not be sold separately," and the recorded deed restriction repeats that "only one (1) unit on the Property may be rented; the other must be occupied by the Owner." Section 15-4-7 states no owner-occupancy requirement for Accessory Apartments; its deed restriction instead "runs with the land and is automatically transferred to the new owner by the sale or transfer of this Property." Utah Code 10-21-303(3)(j) is what lets the city attach the owner-occupancy condition to internal units.

For an Accessory Apartment, "One (1) Parking Space per Bedroom must be provided in addition to the existing requirement for the primary residence," and the citywide parking table repeats "Accessory Apartment: 1 per bedroom." For an Internal ADU it is "One (1) Parking Space per Internal Accessory Dwelling Unit ... in addition to the existing requirement for the Single-Family Dwelling." Parking is permitted only within approved garages and on paved driveways and need not be covered. Tandem parking is allowed where the driveway is at least 25 feet long or to preserve significant vegetation; in residential historic districts a tandem space needs extra approval, an Administrative Permit with findings for an Accessory Apartment and a Planning Commission Conditional Use permit for an Internal ADU.

Both ADU types are staff-reviewed Administrative Permits from the Planning Department, with no public hearing. For Accessory Apartments, "the Planning Department shall approve an Administrative Permit if the requested Accessory Apartment complies with the criteria in Section 15-4-7," though the department "shall impose reasonable conditions to mitigate any impacts to the surrounding neighborhood." For Internal ADUs, "The Planning Department shall review and take Final Action on applications ... pursuant to Section 15-1-8," and 15-1-8 confirms the Planning, Engineering and Building Departments review Administrative Permits with staff final action and an appeal. The one exception: "Internal Accessory Dwelling Units are an Administrative Conditional Use for Single-Family Dwellings designated Significant or Historic on the Park City Historic Sites Inventory," reviewed against the Chapter 15-13 design guidelines and the 15-1-10(E) conditional use criteria.

For an Accessory Apartment, "Nightly Rentals are prohibited in the Accessory Apartment. Rental terms for the Accessory Apartment shall be no less than ninety (90) days," and the recorded Notice to Purchaser repeats the 90-day floor so it binds future owners. For an Internal ADU, "Neither the Single-Family Dwelling or Internal Accessory Apartment may be rented for periods of time less than thirty (30) days," and the deed restriction adds that only one of the two units may be rented while the owner occupies the other. Park City's separate nightly-rental business licence chapter, 4-5-3, does not create an ADU exception; a unit must sit in a zone that allows rentals for the period applied for. The Planning Department can revoke either permit for non-compliance, appealable to the Board of Adjustment.