Portland ADU Regulations & Permits (2025)
Here’s the quick, practical guide to Portland’s ADU rules—what sizes are allowed, how setbacks work, when parking is required, and how to get your permits.
Quick TOC
TL;DR: Portland allows ADUs with clear citywide limits: max size is the lesser of 800 sf or 75% of the primary’s living area; max height is 20 ft (outside setbacks), and no extra on-site parking is required. ADUs can use the City’s ADU SDC Waiver (with a 10-year no-STR covenant). Always confirm your zoning and any overlays.
Portland ADU Rules — 6-point summary
Updated: August 29, 2025. Confirm specifics via the City’s ADU zoning summary and code links below.
ADU size is the lesser of 800 sf or 75% of the primary dwelling’s living area. (Basement ADUs in primary structures ≥5 years old aren’t capped by this limit.)
Detached ADUs: 20 ft max when located outside required setbacks; 15 ft max if within required setbacks.
Detached ADUs must be 40 ft from the front lot line or placed behind the rear wall of the primary house.
No additional on-site parking required for an ADU.
Not required citywide (owner-occ provisions were removed in prior code updates).
ADU SDC Waiver available with a 10-year covenant prohibiting any short-term rentals on the entire property; violation may require 150% SDC payback. Note: the City’s 2025–2028 temporary SDC exemption for new housing does not apply to ADUs (ADUs have a separate waiver program).
Official portals: ADU Zoning Requirements (City of Portland) · BDS ADU Permitting (City of Portland) · Portland Maps (Zoning Lookup) · ADU SDC Waiver Program
Heads-up: Historic resource overlays add design requirements; see Community Design Standards and Historic Resource review paths on the City site.
How to get an ADU permit in Portland (5 steps)
- Check your zoning — Use Portland Maps to confirm zoning/overlays and that ADUs are allowed on your lot.
- Draft your plans — Site plan, floor plans, elevations; meet height, setback, exterior and visitability standards where applicable.
- Optional early help — Book a free 15-minute planner chat or Early Assistance to de-risk corrections.
- Submit permits — Apply through the City portals for zoning/building and any utility/tree/overlay reviews.
- Build & inspections — Pass required inspections; obtain final and certificate of occupancy.
Tip: If you use the ADU SDC Waiver, remember the 10-year “no short-term rentals anywhere on the property” covenant.
Portland ADU FAQs
Is owner-occupancy required for ADUs in Portland?
No. Portland removed owner-occupancy requirements in prior code updates; it is not required today.
What’s the maximum ADU size in Portland?
The lesser of 800 sf or 75% of the primary dwelling’s living area. Basement ADUs in older primaries can be exempt from this cap.
Do I need to provide off-street parking?
No additional on-site parking is required for an ADU.
Are SDC fees waived for ADUs?
Yes—via the ADU SDC Waiver, which requires a 10-year covenant banning any short-term rentals on the entire property. Violations can trigger 150% payback at current rates. Note: the 2025–2028 temporary SDC exemption for new housing excludes ADUs.
How long does permitting take?
City timelines vary with workload. Use the planner appointment or Early Assistance to set realistic expectations.
Can I build a detached ADU in a yard with trees?
Often, but tree protection/roots can affect placement and foundations. Coordinate early with Urban Forestry / BDS.