ADU Rules in Keizer, Oregon

Keizer is a fast-growing city of over 40,000 residents in Marion County, situated on the Willamette River immediately north of Salem. Although Keizer is physically adjacent to Salem and shares much of the same metropolitan area, it is a completely independent city — incorporated in 1982 — with its own city government, Development Code, and permit processes. Keizer has been one of Oregon's faster-growing cities, adding substantial residential development as the Salem metro area expands. ADU construction in Keizer follows the Keizer Development Code alongside Oregon's statewide housing reform mandates.

Oregon Statewide ADU Law — Critical Context

Two Oregon laws govern ADU development in Keizer:

Oregon HB 2001 (2019) requires cities with populations over 10,000 to allow middle housing — duplexes, triplexes, fourplexes, and cottage clusters — in all residential zones. Keizer, with over 40,000 residents, must comply, ending single-family-only zoning and requiring a broader range of housing types to be permitted in residential districts.

Oregon's statewide ADU framework is SB 1051 (2017) plus HB 2001 (2019) middle housing. HB 2098 (2021) is a rental-assistance bill, not ADU.

What Keizer Allows

Under the Keizer Development Code and state law, the following ADU types are permitted in residential zones:

• Detached ADU: A freestanding structure on the same lot as the primary home, with its own kitchen, bathroom, and entrance.
• Attached ADU: An addition connected to the primary dwelling with a dedicated separate entrance and self-contained living facilities.
• Interior Conversion: Converting existing habitable space — basement, attic, or rooms within the primary structure — into a separate dwelling unit.
• Garage Conversion: Converting an existing attached or detached garage into habitable ADU space meeting Oregon building code standards.

One ADU per single-family lot is permitted by right. Keizer's updated code under HB 2001 may allow additional units on eligible lots.

Size and Setback Standards

Oregon law prohibits Keizer from requiring ADUs smaller than 900 square feet or 75% of the primary dwelling's floor area, whichever is less. Typical setback standards in Keizer's residential zones for detached ADUs include:

• Rear setback: 5 feet minimum
• Side setback: 5 feet minimum
• Height: Generally 15–18 feet maximum for detached ADUs

Legal nonconforming structures being converted to ADUs may maintain existing setbacks even if they do not conform to current new-construction standards.

Keizer vs. Salem — Separate Cities

This distinction matters for permit applications: Keizer and Salem are adjacent but completely separate jurisdictions. Keizer has its own:

• Community Development Department
• Development Code
• Building inspection process
• System development charge schedule

If your property address says "Keizer," apply through the Keizer Community Development Department. Salem applications go to a different office and a different code applies.

Urban Growth Boundary

Keizer maintains its own Urban Growth Boundary coordinated with Marion County and Oregon DLCD. ADU permits are issued only for properties within Keizer city limits and UGB. Properties in Marion County outside the UGB are subject to county rural land use regulations.

Willamette River Flood Zone Considerations

Keizer borders the Willamette River and some properties — particularly near the river's western edge — are in FEMA-designated flood hazard zones. ADU construction in flood zones requires:

• Elevated foundations at or above the Base Flood Elevation (BFE)
• Flood-resistant construction materials below the BFE
• Floodplain management compliance

Check your FEMA flood zone designation through FEMA's Flood Map Service Center or Keizer Community Development before finalizing your ADU design.

Seismic Considerations

Keizer, like neighboring Salem, sits in the Willamette Valley and faces moderate to high seismic hazard from the Cascadia Subduction Zone offshore. Oregon DOGAMI maps moderate to high liquefaction potential in Willamette Valley lowland areas. New ADU construction must meet Oregon's seismic building code requirements.

Permit Process

Oregon's statewide ADU framework is SB 1051 (2017) plus HB 2001 (2019) middle housing. HB 2098 (2021) is a rental-assistance bill, not ADU.

Contact: City of Keizer Community Development — (503) 390-3700 — keizer.org/community-development

Disclaimer

ADU regulations in Keizer are subject to change as Oregon continues housing reform implementation. Always verify current requirements with the City of Keizer Community Development Department. This page is for informational purposes only and does not constitute legal or planning advice.