Accessory Structures in Washington County, UT (2026)
5 county-level rules, plus city-specific rules for 1 city in Washington County, Utah.
Verified from official government sources
ADU Rules
Washington County allows one ADU on any lot under 5 acres, with one more per additional 5 acres and a hard cap of four. Size scales with the underlying zone, from 1,500 to 3,500 square feet, and either the ADU or the main house must be owner-occupied to rent the other long-term.
Accessory Dwelling Unit Rules in Washington County
Some RestrictionsWashington County Code of Ordinances § 10-13-18.B.1
B. General Provisions: 1. Number of accessory dwelling units per parcel. An accessory dwelling unit shall only be permitted on a parcel with a single family dwelling. Only one accessory dwelling unit is permitted on a lot or parcel that is zoned less than five (5) acres. On a lot or parcel that is zoned five (5) acres or more, one additional accessory dwelling unit may be approved for each addi...
ADU Owner Occupancy
In unincorporated Washington County, an accessory dwelling unit or the main house must be owner-occupied at least 183 days a year before the other unit can be rented long-term. The rule ties owner-occupancy to the county assessor's primary residential exemption, not just a lease address.
Washington County ADU Owner-Occupancy Rule
Some RestrictionsWashington County Code of Ordinances § 10-13-18.B.4
Occupancy. Either the accessory dwelling unit or the single-family dwelling shall be owner-occupied, and be the primary residence of the owner-occupant with the primary residential exemption as determined by the Washington County assessor's office, in order to utilize the other dwelling as a long term rental dwelling. The non-owner-occupied unit is limited to no more than one family. For the pu...
ADU Rental Restrictions
Washington County bars short-term rental use of either an accessory dwelling unit or its associated single-family home unless a Short Term Rental License is issued under § 10-13-23; renting one of the units long-term instead requires a recorded deed restriction.
Washington County ADU Short-Term Rental Ban
Significant RestrictionsWashington County Code of Ordinances § 10-13-18.B.5
Short term rentals not permitted. Neither the single family dwelling unit, nor the accessory dwelling unit, shall be used or licensed as a short term rental unless specifically permitted in accordance with section 10-13-23.
Shed & Carport Rules
In unincorporated Washington County, a shed or other accessory building can cover no more than 25% of a residential lot and cannot rise above 25 feet without a conditional use permit. It must sit on the same lot as, and cannot go up before, the main dwelling.
Washington County Accessory Building And Shed Rules
Some RestrictionsWashington County Code of Ordinances § 10-13-10
10-13-10: AREA OF ACCESSORY BUILDINGS: No accessory building or accessory dwelling unit, nor group of accessory buildings or ADUs in any residential district shall cover more than twenty five percent (25%) of the lot area. (Ord. 2001-815-O, 12-17-2001, eff. 12-17-2001; amd. Ord. 2021-1196-O, 10-5-2021)
Tiny Homes
A permanent Tiny Home on Foundation can be a primary or accessory dwelling if it meets 2021 IRC Appendix AQ. A Tiny Home on Wheels can only be used as temporary housing under the county's pilot program, capped at 3 years and 3 occupants, and it sunsets automatically on May 15, 2028.
Washington County Tiny Home Rules
Significant RestrictionsWashington County Code of Ordinances § 10-28-1
The purpose of this section is to create a pilot program to provide a temporary housing accommodation during the current housing crisis. The County may terminate this program at any time, but it shall automatically sunset without further action on May 15, 2028. A Recreational Vehicle (RV) or Tiny House on Wheels (THOW) as defined in Section 10-4-1 may be used as a temporary housing accommodatio...
Accessory Structures by City in Washington County
1 cities in Washington County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
All Washington County ordinances
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