State Preemption of Local Zoning in Oregon

What Is State Preemption?

State preemption occurs when a state law overrides local government ordinances in a specific area. In land use, preemption means a city or county cannot adopt zoning rules that are more restrictive than the state standard. If a city tries to prohibit something the state law permits, the state law wins.

Oregon actively uses preemption in housing law. The state has enacted legislation that prohibits local governments from blocking certain types of housing development — most notably accessory dwelling units (ADUs) and lot splits.

ADU Preemption

What local governments cannot restrict:

• ✓Eliminates single-family-only zoning in Oregon cities with population 10,000 or more — duplexes must be allowed by-right in all residential zones
• ✓Cities with population 25,000 or more must allow middle housing (duplexes, triplexes, fourplexes, cottage clusters, townhomes) by-right in all residential zones
• ✓Local jurisdictions must adopt compliant code or be subject to state model code

Lot Split Preemption

Oregon Senate Bill 458 (SB 458) — Middle Housing Lot Division (effective 2022-07-01): SB 458 (effective July 1, 2022) requires Oregon cities that must allow middle housing under HB 2001 to also allow lot divisions for middle housing. Property owners who develop middle housing on a single lot may split the lot to create separate parcels for individual unit ownership — enabling condo-like or fee-simple ownership of townhomes, duplexes, and cottage clusters. Cities may not require a minimum lot size lower than the applicable zone minimum when dividing lots for middle housing.

How Preemption Affects Oregon Cities

State preemption applies to every incorporated city and unincorporated area in Oregon. Select a city below to see how state preemption interacts with local zoning rules.