Portland allows one ADU with a house, two ADUs on qualifying lots, or one detached ADU with a duplex, subject to minimum lot sizes. California state law does not apply here.[1]
| Size limits | Up to 75% of the main home's living area or 800 sq ft, whichever is smaller. The cap does not apply to a basement ADU in a home at least five years old.[1] |
|---|---|
| Height | Detached ADU: 20 ft outside required setbacks, 15 ft inside them. Above 15 ft, materials, roof pitch, trim, eaves and windows must match the house or meet listed standards.[1] |
| Setbacks | Detached ADUs must be 40 ft from the front lot line or behind the rear wall of the house. Detached accessory structures can cover at most 20% of the site.[1] |
| Parking | No extra on-site parking for an ADU.[1] |
| Owner occupancy | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
| Permit steps and timeline | If a standard cannot be met, an Adjustment Review takes about 8 to 10 weeks and is discretionary. The city offers free 15 minute appointments with a planner.[1] |
| Fees | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
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Sources
Every fact above links to an official city or state page. Rules change; check the source before you build.
- [1] Portland.gov: ADU zoning requirements checked Oct 2026
- [2] Portland Zoning Code 33.205 checked Oct 2026