Utah County, UT Accessory Structures: ADU Rules (2026)

116 permits a maximum of one Accessory Dwelling Unit on a lot or parcel, occupied by only one family, accessed by an independent entrance, though it must keep the same street address as the primary home. An internal ADU built inside the existing house has no maximum floor area at all and needs just one additional off-street parking space, but a home addition cannot be converted into an internal ADU for a year after its certificate of occupancy unless an equal or greater share of that addition stays part of the primary dwelling.

Attached and detached ADUs are treated the same way: each is capped at 1,000 square feet of habitable floor area on the standard tier, each needs two additional off-street parking spaces rather than one, and each requires a minimum lot size of one acre. A detached ADU can be built inside a larger accessory structure such as a barn or garage, but it needs its own separate outside entrance with no interior connection between the accessory structure and the dwelling unit, and the floor-area count excludes garages, covered porches, and decks along with any square footage used for the accessory structure's other approved use.

Every ADU, regardless of type, has to meet all adopted state and county health codes and requirements for the provision of culinary water and sewage disposal, and it may carry its own separate gas or electric meter as long as the meter stays in the property owner's name. The Zoning Administrator approves ADUs administratively, without a Planning Commission hearing, in any zone where the use is listed as permitted.