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

Chapter 108-19 governs accessory dwelling units in unincorporated Weber County. Sec 108-19-3 limits a lot to one ADU unless the code specifically allows otherwise, requires the unit to have amenities sufficient to qualify as a dwelling, and mandates a hard-surfaced parking area under Chapter 108-8. Either the ADU or the primary dwelling must be owner-occupied, the owner cannot rent out the owner-occupied unit while away, and the non-owner-occupied side is limited to one family; neither unit can be used or licensed as a short-term rental.

Sec 108-19-4 sets the physical standards: an ADU's footprint, measured by exterior perimeter, must fall between 400 and 1,500 square feet, and gross floor area cannot exceed 2,000 square feet in any case. A detached ADU or the accessory building housing one is capped at 35 feet in height, though on lots of 20,000 square feet or less that height drops to 90 percent of the primary dwelling's height, and the combined footprint of the ADU and primary dwelling cannot cover more than 25 percent of the lot.

The exterior must complement the primary dwelling's architectural style, or be designed by a licensed architect to resemble a barn, outbuilding, or historic structure from the area. Access must be from the side or rear of the building, and ownership of the ADU cannot be split from the primary dwelling except through a lawfully platted subdivision, with a recorded notice on title. Sec 108-19-5 requires a land use permit application with a complete site plan, floor plans, a utility will-serve letter, and owner-occupancy verification; a rented ADU also needs a business license.