Building an ADU in Portland, Oregon
City code and Oregon law · Last reviewed October 9, 2026
In Portland you can add one or two accessory dwelling units (ADUs) to a lot with a house, depending on lot size and zone. An ADU can be up to 800 square feet or 75 percent of the house's living area, whichever is less, and no extra parking is required. Portland Permitting & Development issues the permits, and the city will waive system development charges (SDCs) if you sign a covenant not to use the property for short-term rentals for 10 years. [1][2][3]
| ADUs per lot (single-dwelling zones R20 to R2.5) | One with a house; two if the lot meets minimum size and has frontage on a maintained street (at least one detached) [1][2] |
|---|---|
| ADU with a duplex | One, detached from the duplex, on qualifying lots [1] |
| Max size | 800 sq ft of living area or 75% of the main home's living area, whichever is less [1] |
| Basement conversions | Size cap doesn't apply if the house has been on the site at least 5 years [1] |
| Height (detached ADU) | 20 ft outside required setbacks; 15 ft inside setbacks [2] |
| Placement (detached ADU) | 40 ft back from the front lot line, or behind the rear wall of the house [1][2] |
| Side and rear setbacks | Start at 5 ft; may be larger depending on zone [4] |
| Parking | No extra on-site parking needed [2] |
| Owner occupancy | Not required (barred by state law) [9] |
| System development charges | Waived if you sign a 10-year no-short-term-rental covenant [3] |
| Pre-approved plans | Four free detached ADU plans from the city [4] |
| Short-term rental | Allowed with a Type A or Type B permit, but not if you took the SDC waiver [2][3] |
On this page
What you can build in Portland
Portland's ADU rules are in Zoning Code Chapter 33.205. You can create an ADU by converting part of your house, converting a garage or other accessory structure, adding on to the house, or building a new detached building.
In the single-dwelling zones R20 through R2.5:
- One ADU is allowed with a house or manufactured home on a lot where a house is allowed. With an attached house, the lot must meet the minimum lot area in the code (for example 2,500 square feet in R5).
- Two ADUs are allowed with a house, attached house or manufactured home when the lot meets a larger minimum lot area, for example 3,000 square feet in R5 or 4,200 square feet in R7. The lot must have frontage on a maintained street, and at least one ADU must be detached.
- One ADU with a duplex is allowed on lots that meet that same larger minimum, if the ADU is detached from the duplex.
Two ADUs aren't allowed on lots in the constrained sites ("z") overlay zone. In multi-dwelling, commercial and EX zones, up to two ADUs are allowed with a house regardless of lot size. ADUs can't be added to triplexes, fourplexes, cottage clusters or multi-dwelling buildings. [1][2][4]
Size, height and placement
Size. An ADU's living area "may be no more than 75 percent of the living area of the primary dwelling unit or 800 square feet of living area, whichever is less." For example, a 1,000 square foot house can have a 750 square foot ADU. The cap doesn't apply when you convert the basement of a house that has been on the site for at least five years.
Height. A detached ADU can be 20 feet tall outside the required setbacks, and 15 feet inside them.
Placement and setbacks. A detached ADU must be set back 40 feet from the front lot line or sit behind the rear wall of the house. Side and rear setbacks start at 5 feet but may be larger depending on your zone.
Coverage. A detached ADU can't cover more ground than the main house, and all detached accessory structures together can't cover more than 20 percent of the site.
Looks. Detached ADUs taller than 15 feet must match the house or meet set standards for siding, roof pitch, trim, eaves and windows.
If your design can't meet a standard, you can apply for an Adjustment Review. The city says it takes about 8 to 10 weeks and approval isn't guaranteed. Use the city's Detached Covered Accessory Structures Worksheet on the ADU zoning page to check your design. [1][2][4]
Parking and visitability
"No extra on-site parking is needed for an ADU."
If you build two ADUs with a house, or one ADU with a duplex, at least one unit on the lot must meet "visitability" standards. That means a no-step entrance, a bathroom and at least 200 square feet of living area reachable from that entrance, and door openings at least 34 inches wide. Steep lots and conversions of structures at least five years old are exempt. [1][2]
Fees and the SDC waiver
An ADU needs building permit fees, water service fees and system development charges (SDCs). The city says SDCs "can add significant cost" to an ADU project. Building permit fees are based on the type of permit, the work, its value and the staff who review it.
ADU SDC waiver. The city waives SDCs for new ADUs that are owner-occupied or rented month-to-month or longer. You sign a covenant, binding on all owners of the property for 10 years from final inspection, that no structure on the property, including rooms in the main house, will be used as a short-term rental. Breaking or revoking the covenant costs 150 percent of the current SDC fees. To apply, email the waiver application to the Revenue Division at aducovenant@portlandoregon.gov with your permit number in the subject line.
The city's separate temporary SDC exemption for new housing, for permits issued August 15, 2025 through September 30, 2028, does not cover ADUs.
Even with a waiver, you may pay extra fees if your sewer connection needs to be upsized or separated. The Water Bureau charges only if you need a larger water meter. For budgeting help, see our ADU cost guide and ADU financing guide. [3][4][5]
Garage, basement and attic conversions
You need a building permit to turn an attic, basement or garage into living space. The city warns that ceiling height, emergency exit windows, insulation, ventilation and stairs can make some conversions "expensive, difficult, or even impossible." A garage in a flood hazard area may not be convertible.
Conversions use the city's Accessory Dwelling Unit Code Guide for construction standards. See the city's ADU conversions guide and our garage conversion guide. [4][6]
Renting it out
You can rent an ADU as a Type A accessory short-term rental (up to two bedrooms, stays under 30 days) with the right permit. Type B rentals of three to five bedrooms must meet extra zoning standards.
If you got the ADU SDC waiver, you can't use the ADU, or any other structure on the property, as a short-term rental for 10 years. [2][3]
More homes on one lot: duplexes to fourplexes
Portland's residential infill rules allow a duplex on every single-dwelling lot where a house is allowed, except in the RF zone. In zones R2.5 through R20 they also allow more units per lot, cottage clusters, and no off-street parking requirement. Lots in the "z" overlay can't use these options, and lots on unmaintained streets are generally limited to two units.
A middle housing land division lets you split certain projects, like a fourplex or cottage cluster, into separate lots through an expedited process. For the state rules behind these options, see our Oregon ADU law page. [7]
Code changes to watch
The ADU chapter of the zoning code was last amended effective October 1, 2024. The city lists another zoning code amendment package (Ordinance 192213) taking effect November 1, 2026. Ask a city planner whether it changes anything for your project. [1][8]
Permit steps in Portland
Research your property
Look up your zone, hazards and permit history on PortlandMaps. Work done without permits must be permitted as new work. [4]
Talk to the city (optional, free)
Book a free 15-minute appointment with a city planner, building code reviewer, permit technician, or water, sewer or transportation expert. [4]
Prepare your application
Every ADU needs a site plan. For a new detached ADU you can use one of the city's free pre-approved plans; conversions need architectural plans and, if structural changes are proposed, structural plans. [4]
Apply for the SDC waiver if you want it
Email the signed waiver application and covenant to the Revenue Division at aducovenant@portlandoregon.gov with your permit number in the subject line. Doing this early in permitting can help. [3]
Submit on DevHub
Apply for your building and trade permits on DevHub PDX. If you use a pre-approved plan, write "Pre-Approved ADU" in the project description. [4]
Answer checksheets and pay fees
Reviewers send a checksheet if they need corrections or more information. When the permit is ready, the city tells you the final fees; the permit isn't issued until they're paid. [4]
Build and get inspections
Schedule inspections on DevHub or call the automated inspection line at 503-823-7000. An ADU's electrical work must be done by a licensed electrical contractor. Every permit needs a final approval inspection. [4]
Pre-approved and sample plans
Pre-approved detached ADU plans
Four free building plans (gable or shed roof, slab or crawl space) provided by the City of Eugene and pre-approved to meet building code; not suitable for every lot. [4]
Who to call
-
Portland Permitting & Development, General Inquiries
ADU zoning, permits and plan review questions
-
In-person permit services
1900 SW 4th Ave, Portland, OR
-
Schedule construction inspections
-
City of Portland Revenue Division
ADU SDC waiver applications and covenants (aducovenant@portlandoregon.gov)
Questions people ask
How big can an ADU be in Portland?
Up to 800 square feet of living area or 75 percent of the main home's living area, whichever is less. The limit doesn't apply when you convert the basement of a house that has been on the site at least five years. [1]
Can I build two ADUs in Portland?
Yes, on a lot with a house, attached house or manufactured home in R20 through R2.5 zones if the lot meets the larger minimum lot area (for example 3,000 square feet in R5) and has frontage on a maintained street. At least one ADU must be detached, and one unit must meet visitability standards. [1][2]
Does Portland waive SDCs for ADUs?
Yes, if you sign a covenant that no structure on the property will be a short-term rental for 10 years. Breaking or revoking it costs 150 percent of the current SDC fees. The city's 2025 to 2028 temporary SDC exemption for new housing does not cover ADUs. [3][5]
Do I need parking for an ADU in Portland?
No. The city says no extra on-site parking is needed for an ADU. [2]
Can I do the work myself?
As the homeowner you can sign the building and trade permit applications and do the work yourself, but you can't do an ADU's electrical work. That must be done by a licensed electrical contractor. Contractors must be licensed by the Oregon Construction Contractors Board. [4]
Sources (9)
- Portland Zoning Code Chapter 33.205, Accessory Dwelling Units (10/1/24), City of Portland. Accessed October 9, 2026.
- ADU Zoning, City of Portland, Portland Permitting & Development. Accessed October 9, 2026.
- Apply for an Accessory Dwelling Unit (ADU) System Development Charge (SDC) Waiver, City of Portland. Accessed October 9, 2026.
- Accessory Dwelling Units (ADUs), City of Portland, Portland Permitting & Development. Accessed October 9, 2026.
- Temporary SDC exemption for new housing, City of Portland, Portland Permitting & Development. Accessed October 9, 2026.
- ADU conversions, City of Portland, Portland Permitting & Development. Accessed October 9, 2026.
- Residential Infill, City of Portland, Portland Permitting & Development. Accessed October 9, 2026.
- Title 33 Planning and Zoning (code changes list), City of Portland. Accessed October 9, 2026.
- ORS 197A.425 Accessory dwelling units, Oregon State Legislature. Accessed October 9, 2026.