Zoning & Size Limits
| Requirement | Portland, OR | Eugene, OR |
|---|
| Allowed Zones | All residential zones | All residential zones |
| Max Size (Detached) | 800 sq ft or 75% of primary (whichever is less) | 1,100 sq ft |
| Max Size (Attached) | 1,000 sq ft | 900 sq ft |
| Max Height | 20 ft (outside setbacks); 15 ft (within setbacks) | 35 feet |
| Parking Required | Optional | Optional |
| Owner Occupancy | Not required | Not required |
Setback Requirements
| Setback | Portland, OR | Eugene, OR |
|---|
| Rear Setback | 5 feet | 10 feet |
| Side Setback | 0 feet with easement | 0 feet (easement) |
| Front Setback | 0 feet (alley lot) | 0 feet (alley) |
Permits & Timeline
| Detail | Portland, OR | Eugene, OR |
|---|
| Permit Timeline | 30-45 days | 35-50 days |
| Permit Fees | $1,500-$2,500 | $1,600-$2,700 |
| Impact Fees | Minimal | Minimal |
| Pre-Approved Plans | Extensive pre-approved library available | Available |
Construction Costs
| Cost | Portland, OR | Eugene, OR |
|---|
| Avg Build Cost | $150,000-$300,000 | $140,000-$280,000 |
| Cost Per Sq Ft | $125-$250 | $130-$260 |
| Garage Conversion | $70,000-$160,000 | $65,000-$155,000 |
| Prefab ADU | $100,000-$240,000 | $95,000-$220,000 |
Rental Income Potential
| Rental | Portland, OR | Eugene, OR |
|---|
| 1BR Avg Rent | $1,400-$1,900/mo | $1,200-$1,700/mo |
| 2BR Avg Rent | $1,800-$2,600/mo | $1,600-$2,400/mo |
| Short-Term Rentals | Yes, with registration | Yes, permitted |
| Est. ROI | 6-9% annual return | 7-10% annual return |
Which City Is Better for ADUs?
Portland scores 9/10 while Eugene scores 8/10 on our ADU-friendliness index.
Portland edges ahead overall. Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
Some links on this page are affiliate links. We may earn a commission at no extra cost to you. Learn more
Get Quotes in Your City
Connect with pre-vetted ADU contractors and get free quotes for your project.