ADU rules in Park City

Park City now has two detached paths, each with a lot-size floor. A detached Accessory Apartment under 15-4-7 needs a lot of at least 3,750 sq ft ("Detached Accessory Apartments are allowed on Lots 3,750 square feet or greater"), single-family setbacks, compliance with the plat's Area and Limits of Disturbance, and a height of no more than 18 feet from Existing Grade; it can also be created within a detached garage. Section 15-4-7.2, enacted by Ord. 2026-21 on 10/1/2026 to implement state Senate Bill 284 (Utah Code 10-21-304), adds a separate Detached Accessory Dwelling Unit: "One Detached Accessory Dwelling Unit may be constructed on a Lot that is 11,000 square feet or greater that contains one Single-Family Dwelling," in any zoning district where a single-family dwelling is an allowed use. A Detached ADU is also capped at 18 feet, must follow zoning, disturbance and recorded-plat restrictions, cannot sit in the front yard, and needs proof of adequate utility capacity. Detached Accessory Apartments are barred in the Holiday Ranchettes Subdivision and Accessory Apartments of any form on Main Street area storefront property in HRC and HCB; those footnotes do not mention the new Detached ADU, so check with the Planning Department there.

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, including detached ones on lots of 3,750 sq ft or more, 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," and an Accessory Apartment may not push a structure over the floor area allowed by the code or the subdivision approval. Section 15-4-7.1 sets no floor-area cap for Internal ADUs, only the 6,000 sq ft minimum lot, and Utah Code 10-21-303(1)(b)(i) bars a city from limiting an internal unit's size relative to the house. The new Detached ADU section, 15-4-7.2, also states no floor-area cap: size is bounded by the 18-foot height limit, the zoning district's setback and lot rules, and recorded plat limits, and its parking rule steps up at 2,000 sq ft. Utah Code 10-21-304(4)(b)(i) would let the city bar a Detached ADU larger than the house, but 15-4-7.2 does not adopt that limit.

It depends on which ADU type you build. For an Internal ADU, "The Single-Family Dwelling shall be occupied by the Owner and the Internal Accessory Dwelling Unit shall not be sold separately." For a Detached ADU under the new 15-4-7.2, "The Single-Family Dwelling or Detached Accessory Dwelling Unit shall be occupied by the Owner, and the Detached Accessory Dwelling Unit shall not be sold separately," so the owner may live in either building. Both recorded deed restrictions repeat 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 (the city removed it in 2021); its deed restriction simply runs with the land. Utah Code 10-21-303(3)(j) and 10-21-304(4)(c) are what let the city attach owner occupancy to internal and detached 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 space per unit in addition to the single-family requirement. For a Detached ADU, "Two (2) Parking Spaces per Detached Accessory Dwelling Unit 2,000 square feet or larger or one (1) Parking Space per Detached Accessory Dwelling Unit less than 2,000 square feet must be provided on site in addition to the existing requirement for the Single-Family Dwelling"; the Council set that 2,000 sq ft threshold on the floor, within the state cap of 10-21-304(3). Spaces need not be covered and must be in approved garages or on paved driveways; one tandem space is allowed where the driveway is at least 25 feet long or to save significant vegetation. In residential historic districts a tandem space needs extra approval: Administrative Permit findings for an Accessory Apartment or Detached ADU, a Planning Commission conditional use permit for an Internal ADU.

All three ADU types are staff-reviewed Administrative Permits from the Planning Department, with no Planning Commission 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," with reasonable conditions to mitigate neighborhood impacts. For Internal and Detached ADUs the Planning Department takes Final Action on the Administrative Permit under Section 15-1-8 ("The Planning Department shall review and take Final Action on Administrative Permits for Detached Accessory Dwelling Units pursuant to Section 15-1-8"). Historic properties add review: "Internal Accessory Dwelling Units are an Administrative Conditional Use for Single-Family Dwellings designated Significant or Historic on the Park City Historic Sites Inventory," and a Detached ADU on a Landmark or Significant historic site needs a Historic District Design Review application (a pre-application for non-historic lots in a Historic Zoning District).

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. For a Detached ADU, "Neither the Single-Family Dwelling nor Detached Accessory Dwelling Unit may be rented for less than ninety (90) days." 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." The Internal and Detached ADU deed restrictions both add that only one of the two units may be rented while the owner occupies the other. Park City's nightly rental licence chapter, 4-5-3, creates no ADU exception, and the Planning Department can revoke any of the three permits for non-compliance.