ADU Rules in Beaverton, Oregon

Beaverton, one of Oregon's largest cities and a diverse Washington County suburb southwest of Portland, is home to Nike's world headquarters and a significant Asian-American community. Beaverton is well-served by MAX light rail and situated in the Tualatin River watershed. The city has updated its Development Code to comply with Oregon's landmark housing reform laws, enabling ADU construction on most residential lots.

Oregon Statewide ADU Law — Critical Context

Two Oregon laws are foundational for ADU development in Beaverton:

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. Beaverton, with over 100,000 residents, must fully comply, ending the city's ability to maintain single-family-only zones.

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 Beaverton Allows

Under the Beaverton Development Code and state mandate, the following ADU configurations are permitted in residential zones:

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

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

Size and Setback Standards

Oregon law sets a size floor — Beaverton cannot require ADUs smaller than 900 square feet or 75% of the primary dwelling floor area, whichever is less. Typical setbacks for detached ADUs in Beaverton low-density residential zones include:

• Rear setback: 5 feet minimum
• Side setback: 5 feet minimum
• Height: Generally 18–20 feet maximum for detached ADUs

Legal nonconforming structures being converted may maintain existing setbacks.

Metro Regional Government and Urban Growth Boundary

Beaverton is within the Metro regional government's UGB for the Portland metropolitan area. ADU development is permitted only within Beaverton city limits inside the UGB. Washington County rural properties outside the UGB are governed by county rural land use regulations that do not permit ADUs on most parcels.

Clean Water Services (CWS) and Environmental Constraints

Washington County's Clean Water Services agency manages stormwater infrastructure and natural resource protection throughout the Tualatin watershed, including Beaverton. Properties near:

• Vegetated corridors (stream buffers and natural drainage channels)
• Wetlands or wetland transition areas
• FEMA floodplains along Fanno Creek, Beaverton Creek, and other waterways

…may face construction setback requirements from natural features, limiting where an ADU footprint can be placed. A CWS Site Assessment may be required before permit submission for affected properties.

Seismic Considerations

Beaverton, like all Washington County communities, faces seismic hazard from the Cascadia Subduction Zone. DOGAMI maps significant liquefaction potential in Tualatin Valley lowland areas. New ADU construction must meet Oregon's current seismic building code. Older structures proposed for conversion should be evaluated for seismic vulnerability.

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 Beaverton Community Development — (503) 526-2222 — beavertonoregon.gov

Disclaimer

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