Accessory Structures in Benton County, OR (2026)
4 rules for unincorporated Benton County, Oregon.
Verified from official government sources
ADU Rules
In unincorporated Benton County, an accessory dwelling unit is allowed only where zoning permits it inside an urban growth boundary, and only alongside one legally established detached single-family home. Benton County Code § 91.050 caps the ADU at 900 square feet of habitable space, two bedrooms, two bathrooms, and requires it to sit within 200 feet of the main house.
Benton County ADU Zoning Standards
Some RestrictionsBenton County Code § 91.050
Where permitted by zoning within urban growth boundaries, every accessory dwelling unit (ADU) shall: (1)Be allowed in conjunction with and on the same lot or parcel as one legally established detached single-family dwelling. ... In any event, a maximum of 1 ADU is allowed per single-family dwelling. ... (3)Contain no more than 900 square feet of habitable space. A single-car garage (no larger t...
ADU Rental Restrictions
Once a property in unincorporated Benton County has an accessory dwelling unit, neither the ADU nor the primary house may be rented short-term. BCC § 91.050(11) defines short-term as any lodging agreement under one month, and the prohibition is recorded against the property for future owners.
Benton County ADU Short-Term Rental Ban
Heavy RestrictionsBenton County Code § 91.050(11)
(11)Neither the single-family dwelling nor the ADU may be utilized for short-term accommodation purposes. Short-term accommodations are defined as lodging agreements for a period of less than 1 month.
Shed & Carport Rules
In the Rural Residential zone of unincorporated Benton County, BCC § 63.405(5) lets a shed or other non-residential structure of 120 square feet or less sit with no setback at all, and a slightly larger structure, up to 500 square feet and 20 feet tall, can use a reduced 3-foot side or rear setback.
Accessory Structure Setbacks, Benton County
Some RestrictionsBenton County Code § 63.405(5)
63.405 - Siting Standards. All structures allowed in the Rural Residential Zone shall be sited in compliance with BCC Chapter 99 and the following additional standards: ... (5)A non-residential structure shall not be built within a setback abutting a road. No setback is required for a non-residential structure of 120 square feet or less. A required side or rear setback for an non-residential st...
Tiny Homes
Benton County will not issue a building permit for a tiny house on wheels, classified as a Group R-5 wheeled residential structure under the 2018 Oregon Reach Code. Instead, placement of one on unincorporated land is governed by the recreational-vehicle occupancy standards in Chapter 91 of the Benton County Development Code, not the building permit process.
Tiny Houses on Wheels in Benton County
Significant RestrictionsBenton County Code §§ 11.100, 11.263
11.100 - Plans and Permits. (1)The building official shall neither recognize nor accept a permit application for the construction, reconstruction, alteration, or repair of a Group R-5 wheeled residential structure (commonly referred to as "tiny house on wheels") as defined by 2018 Oregon Reach Code R119.1.2. Placement of such structure is subject to the provisions of BCC Ch. 11.263. ... 11.263 ...
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