Portland is one of America's most ADU-friendly cities, with streamlined approval processes and generous size allowances. The city allows both detached and attached ADUs with minimal setback requirements, making it an ideal market for ADU investment.
Zoning & Size Requirements
| Allowed Zones | All residential zones |
| Max Size (Detached) | 1,200 sq ft |
| Max Size (Attached) | 1,000 sq ft |
| Max Size (JADU) | 800 sq ft |
| Max Height | 40 feet |
| Max Units | 2 ADUs per lot (1 detached + 1 attached) |
Setback Requirements
| Rear Setback | 5 feet |
| Side Setback | 0 feet with easement |
| Front Setback | 0 feet (alley lot) |
| Parking Required | Optional |
| Owner Occupancy | Not required |
| Min Lot Size | 3,500 sq ft |
Permit Process & Fees
| Approval Process | By-right approval (no variance needed) |
| Review Timeline | 30-45 days |
| Permit Fees | $1,500-$2,500 |
| Impact Fees | Minimal |
| Plan Check | 1-2 weeks |
| Pre-Approved Plans | Extensive pre-approved library available |
Get Free ADU Quotes in Portland
Connect with pre-vetted ADU contractors in your area. Free, no obligation.
🔒 Your info is secure. We connect you with up to 3 vetted local contractors. No spam, no obligation.
Construction Costs
| Average Build Cost | $150,000-$300,000 |
| Cost per Sq Ft | $125-$250 |
| Garage Conversion | $70,000-$160,000 |
| Prefab ADU (Installed) | $100,000-$240,000 (installed) |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders in minutes.
Compare ADU Financing Options →Rental Income Potential
| Avg Rent (1 Bedroom) | $1,400-$1,900/mo |
| Avg Rent (2 Bedroom) | $1,800-$2,600/mo |
| Short-Term Rental | Yes, with registration |
| Est. Annual ROI | 6-9% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half. Compare top prefab manufacturers.
Compare Prefab ADUs →Recent Law Changes
What's Changed Recently
- 2024: Increased max detached ADU size to 1,200 sq ft
- 2023: Expanded JADU provisions citywide
- 2024: Reduced parking requirements further
- 2023: Established Middle Housing ordinance allowing 4 units per lot in some zones
Tips for Building an ADU in Portland
- Portland's by-right approval is industry-leading; fastest permitting in the nation
- Pre-approved plans available online; can fast-track your project
- Rental market is strong with good long-term tenant base
- Multiple ADU types allowed on single lot; maximum flexibility for design
Frequently Asked Questions
Can I build an ADU in Portland?
Yes. ADUs are allowed in All residential zones in Portland. The maximum size for a detached ADU is 1,200 sq ft. No owner-occupancy is required.
How much does an ADU cost in Portland?
ADU construction in Portland typically costs $150,000-$300,000. Garage conversions run $70,000-$160,000, and prefab ADUs cost $100,000-$240,000 (installed).
How much can I rent an ADU for in Portland?
Average ADU rents in Portland are $1,400-$1,900/mo for a 1-bedroom and $1,800-$2,600/mo for a 2-bedroom unit.
Do I need parking for an ADU in Portland?
Optional. Check with Portland planning department for the latest Oregon ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Portland?
The permit review timeline in Portland is 30-45 days. Fees range from $1,500-$2,500.
Ready to Build in Portland?
Get free, no-obligation quotes from top-rated ADU contractors in Portland.
Get Free Quotes →