Often, yes. As of October 2026, Portland allows two ADUs with a house in the R20 to R2.5 zones if the lot meets the minimum size, fronts a City-maintained street and is outside the "z" overlay. Only one of the two may be attached to the house, and at least one unit must be visitable.
What tests does my lot have to pass?
- Zone. R20, R10, R7, R5 or R2.5, with a house, attached house or manufactured home.
- Street. Frontage on a City-maintained street.
- Lot size. The minimum lot area the zoning code sets for the zone, which we confirm for your lot.
- Overlay. Not in the "z" overlay, which marks constrained sites.
In multi-dwelling, commercial and EX zones, two ADUs are allowed regardless of lot size or street frontage.
Which combinations work?
Only one ADU may be attached to the house or to another ADU. A basement unit plus a backyard cottage works. So does an attached addition plus a detached unit, or two detached units. Two attached units do not.
What is the visitability rule?
With two ADUs on a house, at least one unit must be visitable for wheelchair users. Portland's standard covers a zero-step entrance, an accessible bathroom and living area, and door widths.
What if I have a duplex?
A duplex can have one ADU, and it must be detached from the duplex. Triplexes, fourplexes and cottage clusters cannot add ADUs.
Is a second ADU worth it?
It depends on lot size, layout and budget. Two units share a single sewer and electrical plan, but they also add coverage, which counts against the 20% limit for detached accessory structures. On a narrow lot, a basement unit plus one cottage is often the practical maximum. We sketch both before you decide.
Related
Sources, as of October 2026: City of Portland, ADU zoning summary (Zoning Code Chapter 33.205, Residential Infill Project amendments).
Updated October 2026