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 1,100 sq ft. Attached ADUs can be up to 900 sq ft. 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 1,100 sq ft. Attached ADUs are limited to 900 sq ft. Junior ADUs (JADUs) have a cap of 750 sq ft. Maximum height is 35 feet. You are allowed up to 1 main ADU + 1 JADU per lot on a qualifying lot.
Rear setback: 10 feet. Side setback: 0 feet (easement). Front setback: 0 feet (alley). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
Optional. 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. The plan check process takes approximately 1-2 weeks. Pre-approved plans availability: Available.
Average ADU rental income in Eugene: 1-bedroom units rent for $1,200-$1,700/mo/month, 2-bedroom units for $1,600-$2,400/mo/month. Short-term rentals: Yes, permitted. Expected ROI: 7-10% annual return.
The minimum lot size for an ADU in Eugene is 4,000 sq ft. 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.