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 governs the approval process. In Portland, the local building department 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: varies — see official source). Attached ADU: 800 sq ft. 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 · Verified June 1, 2026 · Source | See official source |
| Attached ADU | 800 sq ft · Verified June 1, 2026 · Source | See official source |
Permit Fees
ADU Permit Fees in Portland: Plan check fee: Varies. Building permit fee: Varies. Impact fees: None. School fees: None or N/A. Total estimated permit cost: Varies.
| 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 | None |
Permit Timeline
Portland ADU Permit Timeline: Permit timeline has not been confirmed — contact the department for current processing times. Apply through the local building department online permit portal. Phone: (503) 823-7300.
Setback Requirements
ADU Setback Requirements in Portland: Front setback: 40 feet. Side setback: no minimum. Rear setback: no minimum.
Parking Requirements
Parking Requirements: (B) “Reasonable local regulations relating to siting and design” does not include owner-occupancy requirements of either the primary or accessory structure or requirements to construct additional off-street parking.
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: not confirmed — see official source. Multifamily properties: not confirmed — see official source.
- 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
Statewide Preemption
ADU Preemption
Oregon state law preempts local ADU rules — local governments cannot impose stricter standards.
View Oregon preemption detailsFrequently 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 Not specified in Title 33 §33.205; timeline administered by Portland Permitting & Development (PP&D) under Title 24.
Do I need extra parking for an ADU in Portland?
Portland parking rules for ADUs: (B) “Reasonable local regulations relating to siting and design” does not include owner-occupancy requirements of either the primary or accessory structure or requirements to construct additional off-street parking.
Do I have to live on-site to have an ADU in Portland?
Owner-occupancy requirement in Portland: (B) “Reasonable local regulations relating to siting and design” does not include owner-occupancy requirements of either the primary or accessory structure or requirements to construct additional off-street parking.
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