ADU rules in Bountiful

Since Ordinance 2026-08 (adopted September 22, 2026, effective on adoption), a detached ADU is a permitted use reviewed and approved by City Staff in the Single-Family Residential (R), Residential Multiple (RM) Family, and Downtown (DN) Mixed Use zones; it is not allowed in any other zone or on a duplex or multi-family property. The lot must already contain a habitable single-family dwelling, must have at least 8,000 square feet of buildable land (more generous than the 11,000 square foot floor in Utah Code 10-21-304), and the property must be owner occupied. A legally built accessory structure may be converted into a detached ADU with a building permit. The unit must meet the accessory-structure setbacks in 14-4-105(J): 3 foot rear and interior side setbacks at up to 20 feet of height, or 8 foot setbacks at up to 25 feet, these reduced setbacks apply only when the unit sits at least 10 feet behind the front building line, and otherwise the primary-structure setbacks apply. When a side or rear setback is at least 3 but less than 8 feet, the wall facing that property line may have no windows or doors and no exterior stairs, landings, decks or balconies may sit between the unit and that line.

An internal ADU (one created within the primary dwelling and within its footprint at the time of creation) is a permitted use reviewed and approved by City Staff, in the Single-Family Residential, RM, and DN Mixed Use zones only. The property must be owner occupied, only one ADU is allowed per lot, and the structure must keep the outward appearance of a single-family home. A basement ADU may share a common entrance with the main unit if each unit has its own interior door; otherwise the separate entrance must be on the side or rear, with a walkway, and must not make the house look like a duplex. Ordinance 2026-08 left these criteria in place; its new definition describes an internal ADU as one added to or created within the primary dwelling, but the criteria still require the unit to sit within the existing footprint.

A detached ADU must be at least 350 square feet and may not exceed 1,250 square feet, and may not be built on a lot with less than 8,000 square feet of buildable land; Ordinance 2026-08 kept both figures after the Planning Commission discussed raising or removing the cap and left it for future study. Height comes from the accessory-structure standards: 20 feet to the peak and 15 feet to the eave under the standard option, or up to 25 feet with a 20 foot eave under the ADU-only enhanced option that requires 8 foot rear and side setbacks. All accessory structures together may cover no more than 10 percent of the lot. The internal ADU criteria set no square-foot limit, but an internal ADU must fit within the footprint of the primary dwelling as it stood when the unit was created.

For both detached and internal ADUs the property owner must occupy either the principal unit or the ADU as a permanent residence and may at no time receive rent for the owner-occupied unit. The application must include proof of owner occupancy (voter registration, vehicle registration, driver's license, county assessor records, or similar). A deed restriction limiting the property to single-family use, prepared by the Planning Director and signed by all owners, must be recorded with the Davis County Recorder before the ADU is occupied, or before the building permit is issued if one is required. Utah law leaves this requirement to cities for internal units, and Utah Code 10-21-304(4)(c), in force since October 1, 2026, expressly allows it for detached units.

Adequate off-street parking is required for both the primary residence and the ADU, and one off-street space must be provided for the ADU on top of the parking required for the principal unit at the time of construction. The rule is identical for detached and internal units and was left unchanged by Ordinance 2026-08; it sits within the state caps of one space for a detached unit under 650 square feet and two at or above that size. Any additional occupant vehicles must be parked off-street in code-compliant areas; on-street parking may be used only within the limits of the Bountiful Traffic Code. A detached ADU designed for vehicle parking must be connected to the street by a paved driveway.

Both ADU types are now permitted uses reviewed and approved by City Staff. Ordinance 2026-08, adopted September 22, 2026 to comply with Utah Code 10-21-304, changed detached ADUs from a conditional use decided by the Administrative Committee to a Staff-approved permitted use, and removed the detached ADU conditional use permit row from the Approval and Review Bodies table in 14-2-111. It is unlawful to live in, or let anyone live in, an ADU that has not received a permit from the Planning Department. Applications for both types are filed through the city's CityInspect portal. The R, RM and DN use tables and the city's ADU web page had not been updated and still list detached ADUs as conditional at this check.

An internal ADU is defined as a unit created for a long-term rental of 30 consecutive days or longer, and the internal ADU criteria still carry a sentence saying that effective April 1, 2022 short term rentals of 30 days or less are prohibited. Chapter 14 separately allows short-term rentals, but only inside an approved accessory dwelling unit and only in the R, RM and DN zones: renting an entire single-family home, duplex or multi-family property short term is unlawful. A short-term rental needs its own permit, reviewed in a public meeting by the Administrative Committee after mailed notice to owners within 300 feet and a posted sign, costing $225 (or $100 if the applicant already has an ADU or applies for one at the same time). The permit does not run with the land, requires a city business license, and the owner may at no time receive rent for the unit they occupy themselves.