Union County

Where are ADUs allowed in Union County?

  • Union County (outside city limits): Permitted in R1, R2, R3, R4 (no str), since August 2024. 1 application, not approved

  • La Grande: Permitted in Hillside Development Residential, Rural Residential, Low Density Residential, Medium Density Residential, High Density Residential, Residential Professional, str allowed

  • Island City: Permitted in Single Family Residential, Residential Duplex, Residential Environmental (working on updating the code)

  • Union: Permitted in General Commercial (for owners and employees), Heavy Commercial (for owners and employees), Commercial Amusement (for employees) (CU), Exclusive Farm Use (for family of farm operators) (CU)

  • Cove: Yes, in residential areas, str allowed, no ADUs developed

  • Elgin: Not permitted

Image: Cove Zoning Map
Image: Island City Zoning Map
Image: La Grande Zoning Map

CONFIRM WHERE THE PROPERTY IS LOCATED.

  • If the property is outside city limits (unincorporated Union County) - The county has different ADU rules (e.g., 2-acre minimum, 900 sf max, STR ban) than cities. If you are looking at placing an ADU outside city limits, follow this information from Union County.

  • If the property is inside the La Grande city limits, see these steps.

Resources

State Requirements

  • Meet Oregon building code requirements - Your ADU must comply with the Oregon Residential Specialty Code (ORSC) (2023 edition, mandatory statewide). The ORSC covers structure, egress, fire/life safety, energy, etc. If you’re converting a garage/shed, expect upgrades to meet current habitable-space standards.

  • Asbestos rule - If any demolition is part of your project, Oregon law may require an asbestos inspection by an accredited inspector, and you must keep the report on-site. The City’s ADU application specifically calls this out - plan for it.

  • Call 811 before you dig - At least two full business days before excavation, submit a locate request (Oregon 811) for underground utilities. This is required statewide.


FAQs and Common Pitfalls (La Grande & Oregon)

  • Owner-occupancy and parking requirements: Oregon law prohibits cities from requiring owner-occupancy of the primary or ADU and from imposing additional off-street parking as a condition of ADU approval (cities may still set siting/design standards).

  • Short-term rentals (Airbnb/VRBO): La Grande has been working on short-term lodging rules. If you plan to use an ADU as a short-term rental, check current City policy before you invest—some drafts allowed one STR per property citywide with limits by zone, but always confirm the current adopted rules with Planning.

  • Front setbacks and height details: La Grande’s 2023 code amendments outline ADU height and setback language (e.g., 21-ft height, setback relationships to the primary house). Verify the exact numbers for your lot and zone when you submit.

  • Nonconforming conversions: If converting a nonconforming structure (e.g., encroaching setbacks), a substantial alteration (≥ 50% of assessed value) can trigger full compliance of structure/site—talk to Planning before you proceed.