ADU Rules in Portland, OR (2026)
ADU rules, permit requirements, size limits, and fees for Portland, OR. Source-cited from official municipal code.
Yes, ADUs are allowed in Portland, OR.
Portland, OR permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law actively preempts local restrictions, making ADU approval a streamlined ministerial process. In Portland, the Portland Bureau of Development Services (BDS) handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Portland.
ADU Size Limits
ADU Size Limits in Portland: Detached ADU: up to 800 sq ft (max height: 20 feet). Attached ADU: 75% of primary dwelling up to 800 sqft. Portland does not use the California JADU concept. Detached ADU (Accessory Dwelling Unit) maximum is 800 sqft per Portland Zoning Code Section 33.205. Attached ADUs are limited to 75% of the primary dwelling floor area, maximum 800 sqft. Garage conversions to ADU limited to existing footprint. Portland allows one attached and one detached ADU per single-family lot.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | 800 sq ft | 20 feet |
| Attached ADU | 75% of primary dwelling up to 800 sqft | Same as primary dwelling height limit |
Permit Fees
ADU Permit Fees in Portland: Plan check fee: $1,500–$4,000 depending on project value. Building permit fee: $1,200–$3,500. Impact fees: Transportation and parks system development charges (SDCs) apply — typically $10,000–$20,000 for new ADU. School fees: School SDCs may apply for ADUs — contact Portland BDS for current rates. Total estimated permit cost: $3,000–$8,000 in permit fees plus system development charges. Portland's System Development Charges (SDCs) for transportation, parks, and water/sewer can be significant — typically $10,000–$25,000 for a new detached ADU. SDC deferrals available for affordable housing ADUs. Fee schedule: https://www.portland.gov/bds/permit-fee-schedule
| Fee Type | Amount |
|---|---|
| Plan Check | $1,500–$4,000 depending on project value |
| Building Permit | $1,200–$3,500 |
| Impact Fees | Transportation and parks system development charges (SDCs) apply — typically $10,000–$20,000 for new ADU |
| School Fees | School SDCs may apply for ADUs — contact Portland BDS for current rates |
| Total Estimate | $3,000–$8,000 in permit fees plus system development charges |
Permit Timeline
Portland ADU Permit Timeline: Portland BDS (Bureau of Development Services) processes ADU permits ministerially. Standard ADU: 4-8 weeks plan review. Pre-approved standard plan sets available from BDS reducing review time. Construction typically 3-9 months. Permits expire if construction not started within 2 years. Apply through the Portland Bureau of Development Services (BDS) online permit portal. Phone: (503) 823-7300.
Setback Requirements
ADU Setback Requirements in Portland: Front setback: Same as zone standard. Side setback: 5 feet. Rear setback: 5 feet. Detached ADU setbacks: 5 ft side and rear in most residential zones per Portland Zoning Code 33.205.040.D. Front setback follows applicable zone standard. ADU may be placed within required rear setback if setback from rear property line is at least 5 ft. Corner lots: ADU must meet the street setback of the applicable zone on both street frontages.
Parking Requirements
Parking Requirements: No additional parking required for ADUs in Portland. Portland eliminated off-street parking requirements for ADUs in 2013, predating Oregon's statewide elimination. ADUs within 500 feet of a frequent service transit line have no parking requirement per Portland Zoning Code 33.266. Portland also reduced citywide parking minimums through the 2018 Central City 2035 plan.
Restrictions & Requirements
- ADU must comply with Portland Zoning Code Title 33 objective standards
- One ADU per single-family dwelling (attached OR detached — additional ADU type requires middle housing approval)
- ADU cannot be sold separately from primary dwelling under single-family zoning
- Short-term rental of ADU (less than 30 days) requires separate Type A or B permit
- ADU must have permanent foundation — no recreational vehicles
- Exterior design of detached ADU must be compatible with primary dwelling per 33.205.040.F
How Many ADUs Are Allowed?
Number of ADUs Allowed in Portland: Single-family lots: 1 ADU per single-family lot (attached or detached); middle housing rules allow up to 4 units total via HB 2001. Multifamily properties: Varies by RM zone — RM1/RM2 allow 1 ADU per existing unit; RM3/RM4 allow additional units per floor area ratio. Under Portland's middle housing regulations implementing HB 2001, single-family lots in R20 through R2.5 zones may have up to 4 units (duplex, triplex, fourplex, or cottage cluster of 4). ADU allowances stack with middle housing allowances in RM zones.
Single-Family Lots
1 ADU per single-family lot (attached or detached); middle housing rules allow up to 4 units total via HB 2001
Multifamily Properties
Varies by RM zone — RM1/RM2 allow 1 ADU per existing unit; RM3/RM4 allow additional units per floor area ratio
State Law & Preemption
State Preemption: Oregon House Bill 2001 (2019) eliminates single-family-only zoning in cities with population 10,000 or more. Portland must allow middle housing (duplexes, triplexes, fourplexes, cottage clusters, townhomes) by-right in all residential zones. Portland was already ADU-friendly prior to HB 2001 and remains one of the most permissive cities for ADU development. SB 458 (2021) allows lot splits for middle housing development.
Historic District Considerations
Historic District Requirements: Portland has 32 historic districts where additional design review may be required for ADU construction. Design review approval is required before obtaining a building permit for properties in historic overlay zones. Portland has 32 Historic Conservation Districts and numerous individual Historic Landmarks. Properties in Conservation Districts require Historic Review for exterior alterations visible from the public right-of-way. Landmarks require Historic Review for all exterior changes. Review by Portland Historic Landmarks Commission or staff-level review for minor alterations. Historic resources database: https://www.portland.gov/bps/historic-resources Look up historic district boundaries at: https://www.portland.gov/bps/historic-resources/historic-districts
Frequently Asked Questions
Can I build an ADU in Portland?
Yes. Portland, OR allows accessory dwelling units. On a single-family lot you can build 1 ADU per single-family lot (attached or detached); middle housing rules allow up to 4 units total via HB 2001.
How big can an ADU be in Portland?
The maximum size for a detached ADU in Portland is 800 square feet.
How long does it take to get an ADU permit in Portland?
The typical ADU permit timeline in Portland is Portland BDS (Bureau of Development Services) processes ADU permits ministerially. Standard ADU: 4-8 weeks plan review. Pre-approved standard plan sets available from BDS reducing review time. Construction typically 3-9 months. Permits expire if construction not started within 2 years.. Total estimated permit fees are $3,000–$8,000 in permit fees plus system development charges.
Do I need extra parking for an ADU in Portland?
No, Portland does not require additional parking for ADUs.
Do I have to live on-site to have an ADU in Portland?
No, owner-occupancy is not required for ADUs in Portland.
Source: Portland City Code Title 33, Section 33.205 — Accessory Dwelling Units; Oregon Revised Statutes 197A.420 (HB 2001 codification). Last verified April 5, 2026. View source