Everything homeowners ask about building an ADU in Eugene — answered with 2026 data.
Yes, ADUs are allowed in All residential zones in Eugene, OR. The maximum size for a detached ADU is 800 sq ft (or 10% of lot area, whichever is smaller). Attached ADUs can be up to 800 sq ft (or 10% of lot area, whichever is smaller). Eugene has an ADU-friendliness score of 8/10. Check our full Eugene ADU rules page for complete zoning details.
ADU construction in Eugene typically costs $140,000-$280,000. The cost per square foot averages $130-$260. Garage conversions are more affordable at $65,000-$155,000, while prefab ADUs cost $95,000-$220,000. Permit fees add $1,600-$2,700 to your budget. See our detailed Eugene ADU cost guide.
Detached ADUs in Eugene can be up to 800 sq ft (or 10% of lot area, whichever is smaller). Attached ADUs are limited to 800 sq ft (or 10% of lot area, whichever is smaller). Junior ADUs (JADUs) have a cap of N/A (Oregon does not use a separate JADU category). Maximum height is Detached ADUs set back from the front are height-limited (approx. 18-20 ft); confirm with Eugene Planning for your zone. You are allowed up to 1 ADU per detached single-family dwelling on a qualifying lot.
Rear setback: 10 feet. Side setback: 5 feet (interior yard); Confirm with Eugene Planning. Front setback: 10 feet; Confirm with Eugene Planning. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
Not required (Oregon HB 2001 prohibits ADU-specific parking mandates). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Eugene is typically 35-50 days. Plan check: 1-2 weeks. Pre-approved plans availability: Available.
Average ADU rental income in Eugene: 1-bedroom units rent for $1,200-$1,700/month, 2-bedroom units for $1,600-$2,400/month. Short-term rentals: Yes, permitted. Expected ROI: 7-10% annual return.
The minimum lot size for an ADU in Eugene is No ADU-specific lot minimum under Oregon HB 2001; standard zone lot standards apply (legacy local code referenced 6,100 sq ft / 12,500 sq ft flag lots, no longer enforceable as an ADU barrier) — Confirm with Eugene Planning. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Eugene, a garage conversion typically costs $65,000-$155,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.