Oregon ADU Laws: Statewide Rules That Override Local Restrictions

Oregon's approach to ADUs is among the most progressive in the country. A series of state laws — beginning with SB 1051 (2017) and expanded by HB 2001 (2019) and SB 458 (2021) — opened up ADU development statewide by overriding restrictive local zoning rules.

What SB 1051 (2017) started

SB 1051 was Oregon's foundational ADU law: it required cities with populations over 2,500 to allow at least one accessory dwelling unit on each lot zoned for single-family homes (codified at ORS 197.312). HB 2001 (2019) then went further, requiring larger cities to allow duplexes and other middle housing in single-family zones.

What SB 458 (2021) added

• Made it easier to split lots in urban areas to legally separate ADUs from the main house.
• Required that ADUs meeting state minimum standards be approved ministerially — no discretionary review.
• Reduced the ability of local governments to impose design requirements that increase cost without serving a legitimate planning goal.

Size and setback standards

In Oregon cities subject to the state mandate, a detached ADU may be up to 900 sq ft on lots smaller than 2,500 sq ft, and up to 1,200 sq ft on larger lots. Setback requirements cannot exceed 4 feet from the rear or interior side yard. Maximum height of 25 feet is typical but varies by locality.

Rules vary by city size and whether the city has adopted its own compliant code. Always verify with your local planning department.