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 [1][2]
Yes, you can build an ADU in Portland. A detached ADU can be up to 800 sq ft under current Oregon and Portland zoning rules.
| Allowed Zones | All residential zones |
| Max Size (Detached) | 800 sq ft or 75% of primary (whichever is less) |
| Max Size (Attached) | 800 sq ft or 75% of primary living area (same cap as detached; no separate 1,000 sq ft limit) |
| Max Size (JADU) | N/A (Oregon and Portland do not use a JADU category) |
| Max Height | 20 ft (outside setbacks); 15 ft (within setbacks) |
| Max Units | 2 ADUs per lot (1 detached + 1 attached) |
Setback Requirements [1][2]
Portland requires a rear setback of about 5 ft for a detached ADU, and no additional parking is required. Owner-occupancy is not required — you can rent it out without living on the property.
| 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 | Varies by zone (no single citywide minimum) |
Permit Process & Fees [3]
An ADU permit in Portland typically costs ~$1,900 permit and plan review; plus System Development Charges (SDCs) of about $19,000 - see impact fees and takes 30-45 days, through a ministerial, by-right review.
| Approval Process | By-right approval (no variance needed) |
| Review Timeline | 30-45 days |
| Permit Fees | ~$1,900 permit and plan review; plus System Development Charges (SDCs) of about $19,000 - see impact fees |
| Impact Fees | SDCs total roughly $18,900 for a detached ADU (Parks ~$7,100, Sewer ~$6,600, Transportation ~$2,900, Water ~$2,300); waivable through Portland's ADU SDC Waiver if the unit is not used as a short-term rental (10-year covenant, application required) |
| Plan Check | 1-2 weeks |
| Pre-Approved Plans | Extensive pre-approved library available |
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Construction Costs [4][5]
Building an ADU in Portland typically costs $150,000-$300,000 ($125-$250 per sq ft); a garage conversion runs $70,000-$160,000.
| 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 |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [6][7]
A 2-bedroom ADU in Portland rents for around $1,800-$2,600/mo, an estimated 6-9% annual return.
| 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
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Recent Law Changes
What's Changed Recently
- Oregon HB 2138 (signed July 2025): a statewide middle-housing law that retroactively voids private CC&R/HOA covenants restricting ADUs and middle housing, operative Jan 1, 2027
- A basement ADU in a structure at least 5 years old is exempt from the 800 sq ft / 75% size cap (there is no separate 1,000 sq ft basement limit)
- Detached ADUs now allowed on duplex lots (previously single-family only)
- Street-facing entrance restriction lifted — two street-facing entrances now allowed
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
ADU Builders in Portland
Looking for an ADU builder in Portland? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Portland homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- ADU Zoning Requirements | Portland.gov Planning Department — Accessed 2026-02-24
- Portland Zoning Code 33.205 — Accessory Dwelling Units Municipal Code — Accessed 2026-02-24
- ADU Permits | Portland.gov Planning Department — Accessed 2026-02-24
- Angi — ADU Construction Cost Data Market Data — Accessed 2026-02-24
- Angi — Local ADU Contractor Costs Market Data — Accessed 2026-02-24
- Zillow Rental Manager — Market Rent Data Market Data — Accessed 2026-02-24
- HUD Fair Market Rents Government Data — Accessed 2026-02-24
- Accessory Dwelling Units (ADUs) | Portland.gov Planning Department — Accessed 2026-02-24
- Oregon ADU Regulations — DLCD Government Data — Accessed 2026-02-24
Frequently Asked Questions
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