Accessory Dwelling Units (ADUs, SB391)

Rural Accessory Dwelling Units - SB 391

The Lane County Planning Commission will be reviewing code amendments to allow ADUs in rural Lane County at a public hearing on Tuesday, July 19, 2022 at 7 PM with a work session at 6 PM. The hearing will be held in a hybrid format, with in-person and remote call-in options. See the public hearing notice for more information. As materials are made available for the public hearing they will be posted at the Lane County Planning Commission webpage.
On June 23, 2021, Governor Kate Brown signed Senate Bill (SB) 391 into Oregon law. This law allows rural accessory dwelling units (ADUs) in rural residential zoned areas, subject to certain conditions. While the bill included an emergency clause, meaning it went into effect on June 23, 2021, the day it was signed by the Governor, the bill includes several requirements that prevent the County from allowing ADUs at this time. More information about this is below.

The full text of the enrolled bill can be viewed here

Overview of the SB (not an exhaustive list; SB 391 includes some additional requirements):

Counties may allow one ADU on lands zoned rural residential if the following conditions are met:

  • The county adopts an ordinance to allow ADUs in rural residential zoned areas (lands subject to LC 16.290, but not lands subject to LC 16.231)
  • The lot or parcel is at least two (2) acres in size
  • One single family dwelling is sited on the lot or parcel
  • The lot or parcel is served by a fire protection service provider
  • Complies with all applicable state laws relating to sanitation and wastewater disposal
  • Limited to 900 square feet of useable floor space
  • Within 100 feet of the existing single family dwelling
  • The lot or parcel and ADU comply with rules of the State Board of Forestry under ORS 477.015 to 477.061 and Oregon residential specialty code relating to wildfire hazard mitigation


  • Cannot be utilized for vacation occupancy
  • The ADU cannot be separated from the primary dwelling by land division
  • Are not allowed in urban reserves
  • More than one ADU on a lot or parcel

Required development standards (these land use regulations must be adopted by the County):

  • Adequate setbacks from adjacent lands zoned for resource use
  • Adequate access for firefighting equipment, safe evacuation and staged evacuation areas
  • Adequate defensible space and fuel break standards where the ADU is not subject to ORS 477
  • Other criteria or standards that may be adopted by the County

County Process and Implementation:

  1. A county must decide whether to allow ADUs or not. If yes, then the Board of County Commissioners (“Board”) must adopt an ordinance to allow ADUs in Lane County Code. 
  2. The Board will decide if they would like to adopt the text of the bill as is, or if they would like to modify certain provisions. This bill allows counties to place additional conditions (be more restrictive) than the law.
  3. If the Board would like to develop and adopt additional local standards, they will need to provide policy guidance for staff to develop the local standards.
  4. Once the Board decides whether to adopt the bill as is or with additional local standards, the public hearing process to adopt the law into Lane County Code will begin. Draft code will be presented to the Lane County Planning Commission and the Board of Commissioners to consider adopting ADU provisions.

*Important to note
, while this law is effective immediately and counties may adopt ordinances to allow ADUs, local governments cannot implement the law (meaning they cannot allow or approve ADUs) until the adoption of the statewide wildfire maps and until the County adopts certain land use regulations as required by the bill. A requirement of the bill is that statewide wildfire risk maps have been adopted and that the ADU be constructed in compliance with the Oregon residential specialty code relating to wildfire hazard mitigation for the mapped wildfire risk. Until that mapping is complete, the County cannot implement this section of the bill. The State is required to adopt the maps by June 30, 2022. The State is also required to identify and recommend needed updates to the statewide land use planning program, local comprehensive plans, and zoning codes to incorporate a statewide wildfire risk map and to minimize wildfire risk, in a report to the Legislative Assembly by October 1, 2022.