ADU rules in Bluffdale

Detached ADUs (D-ADUs) are a permitted use in all primary residential zoning districts, mixed use zones, and special district zones on lots that contain no more than one single-family dwelling; the residential and agricultural use table lists ADUs as permitted (P) in the A-5, A-2, R1, R2, R3, R4 and R-MF zones. There is no minimum lot size for a D-ADU, so the city already exceeds Utah Code 10-21-304(1)(a), in force since October 1, 2026, which requires a specified municipality to permit a detached ADU on any single-family lot of 11,000 sq ft or more. A D-ADU must sit in the rear or side yard, meet the zone's accessory-building setbacks, height and lot coverage, and have at least 400 sq ft of habitable space.

Internal ADUs (I-ADUs) are a permitted use in all primary residential zoning districts, mixed use zones, and special district zones within single-family dwellings on parcels greater than 6,000 sq ft. An I-ADU must be contained within the footprint of the primary dwelling (it may sit above an attached garage), and the exterior may not be altered so the house no longer looks like a single-family dwelling. Bluffdale regulates internal rather than attached ADUs generally; Utah Code 10-21-303 makes an internal ADU a permitted use in residential zones and lets a city bar them on lots of 6,000 sq ft or less.

The city code caps any ADU at 50% of the total square footage of all floors of the primary dwelling as shown in Salt Lake County Assessor records, excluding attached garage space, and requires a D-ADU to have at least 400 sq ft of habitable space. For detached units the cap is allowed by Utah Code 10-21-304(4), which lets a city regulate structure size. For internal units it conflicts with Utah Code 10-21-303(1)(b)(i), which bars a city from restricting "the size of the internal accessory dwelling unit in relation to the primary dwelling"; the code has not been amended to exempt internal ADUs, so confirm with the Planning Department before relying on the cap for an internal unit.

The owner of record must occupy the primary dwelling as their primary residence, or live in the approved ADU, and the application must include a statement of owner occupancy. If the owner stops living on the property, the ADU may not be rented, leased, or occupied. Exceptions cover a bona fide temporary absence of three years or less (military service, job assignment, sabbatical), placement in a hospital, nursing home or assisted-living facility, and up to 90 days during a change of ownership. Utah Code 10-21-304(4)(c) and 10-21-303(3)(j) allow owner-residency rules of this kind.

The city code requires at least one off-street stall for an internal ADU and two for a detached ADU, in addition to the primary dwelling's required parking, reserved for ADU occupants, on an all-weather surface, and located behind the front plane of the house; a garage stall counts only if it is extra and not tandem. The two-space rule for every D-ADU conflicts with Utah Code 10-21-304(3)(c), in force since October 1, 2026, under which the city's regulation may not "require more than one on-site parking space assigned to a detached accessory dwelling unit that is smaller than 650 square feet." The city has noticed a text amendment (Application 2026-29) to reduce D-ADU parking for units under 650 sq ft, but as of October 21, 2026 it had not been adopted, so the two-space text is still the printed rule.

ADUs are a permitted use in eligible zones (shown as P in the residential and agricultural use table), consistent with Utah Code 10-21-304(3)(a), which bars a conditional use permit for a detached ADU in a primarily residential zone. Before the unit may be used or rented, the owner needs an ADU Permit from the Land Use Authority and a building permit with completed inspections, and the city records a notice of accessory dwelling unit against the property.

An ADU may not be rented or leased for less than 30 consecutive days, only one rental agreement may be in effect at a time, and the primary dwelling may not be separately rented while it has an ADU. Ordinance 2026-13 (July 22, 2026) legalized short-term rentals of complete homes in residential zones but defines a short-term rental as a complete dwelling unit "not including an accessory dwelling unit," so ADUs remain excluded. City Council members discussed allowing short-term rentals in ADUs at a September 23, 2026 work session; no amendment had been proposed or adopted as of October 21, 2026.