Accessory Dwelling Unit Code Amendments

Owners of residentially zoned property within urban growth boundaries (outside of city limits) in Benton County may apply to establish an accessory dwelling unit (ADU), beginning July 2, 2018.  (Within city limits, contact the city to determine whether an ADUs is allowed.)  The Accessory Dwelling Unit (ADU) development standards and the original ordinance are available below under Supporting Documents. To apply, contact the Community Development Department.

On June 19, 2018 the Benton County Board of Commissioners adopted amendments to the County Development Code that allow and establish standards for accessory dwelling units (ADU). These amendments will take effect June 30, 2018.

ADUs are subject to several standards that, in summary, include:

  • 1 ADU per single-family dwelling
  • Maximum habitable space of 900 square foot
  • Maximum attached garage of 300 square feet
  • Maximum of 2 bedrooms and 2 bathrooms
  • Demonstration of 50% greater well-water supply than is required of a single-family dwelling
  • Located no more than 200 feet from single family dwelling
  • Road approach to be shared with single-family dwelling, and driveway to meet fire district requirements
  • Required owner-occupancy of either the single-family dwelling or the ADU
  • Short-term rental (less than 30 days) prohibited for both the ADU and single-family dwelling
  • Compliance with building code, septic system rules and road approach regulations

Refer to the Development Code for the full requirements.

The standards were developed and adopted through a local public process. The standards are intended to be consistent with the goal of expanding affordable housing opportunities in the County, while continuing to protect neighboring properties from negative impacts and environmental hazards.

Oregon Senate Bill 1051 was developed with the primary purpose of expanding housing opportunities within the state and, among other things, required most local jurisdictions to allow ADUs within urban growth boundaries. 

The Benton County Community Development Department held a public information and input session in April 2018. The Planning Commission held a public hearing in May, followed by a Board of Commissioners public hearing in June 2018.