Accessory Dwelling Unit (ADU) Rules for Unincorporated Washington, OR

ADU State Law

What can you build in Oregon?

• –In urban growth areas, Oregon law requires cities and counties to allow at least one ADU on lots zoned for detached single-family homes.
• –Local jurisdictions cannot require owner occupancy for ADUs, but may regulate short-term or vacation rentals.
• –There are no statewide limits on ADU size, height, setbacks, lot size, or floor area ratio. Local zoning rules apply.
• –Parking requirements, if any, are set by the local jurisdiction, subject to state limitations.
• –Some cities may allow more than one ADU per lot, depending on local code.
• –Oregon law does not require counties to allow ADUs in rural residential zones. Whether an ADU is allowed depends on county zoning.
• –ADUs in rural residential areas cannot be used for short-term or vacation rentals.
• –Additional requirements may apply related to wildfire risk, water supply, septic capacity, and fire access.
• –Counties may impose additional restrictions beyond state law or choose not to allow ADUs at all.
• –If a county allows ADUs, state law imposes strict limits, including a minimum 2-acre lot size, a maximum ADU size of 900 sq ft, a location within 100 ft of the primary dwelling, and a limit of one ADU per parcel.