Lehi, UT Accessory Structures: ADU Rules (2026)

030 authorizes one Accessory Dwelling Unit (ADU) inside an owner-occupied single-family detached home, but only after a builder or homeowner obtains all required permits and approvals from the Planning Division. The ADU cannot change the home's exterior appearance as a single-family residence and must show no outward evidence that more than one family lives there. A minimum lot size of 6,000 square feet is required under subsection E, and ADUs are barred entirely from any parcel identified on the city's ADU Restricted Area Map under subsection D.

A physical connection, such as a locking door, must join the primary dwelling to the ADU so the space could revert to ordinary living area if the ADU use ends. One off-street parking stall measuring at least 9 by 20 feet is required, separate from and not in tandem with the primary home's parking, reached by a lighted walkway built of approved material. 040 raises the minimum lot size to 11,000 square feet, requires the unit to sit to the side or behind the primary home and at least 6 feet away from it, and caps its finished living area below that of the primary home.

Only one ADU is permitted per lot, whether internal or detached; an owner may switch from one type to the other only by filing a new application that meets every current requirement.