ADU rules in Portland, OR — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Portland allows accessory dwelling units (ADUs) on every single-dwelling residential lot under PCC 33.205. ADUs can be attached, internal (basement/attic conversion), or detached and may be up to 75% of the primary dwelling's living area or 800 sq ft, whichever is greater. No additional parking is required, no owner-occupancy is required, and System Development Charges are waived under PCC Title 17.13.
PCC 33.205 (Accessory Dwelling Units) is among the most permissive ADU codes in the country. Key standards: maximum size is the greater of 800 sq ft or 75% of the primary dwelling's living area (PCC 33.205.040); maximum height 20 feet for detached ADUs (taller if matching the primary dwelling under RIP standards); only one ADU per single-dwelling site unless additional units are permitted as middle housing under PCC 33.110 (RIP allows up to a duplex, triplex, or fourplex in many R-zones). Setbacks match the underlying zone (typically 5 ft side/rear in R5). No off-street parking is required for ADUs. The permit process is administered by Portland BDS through the residential permit pathway; combined fees plus the System Development Charge waiver (PCC 17.13) typically keep total permit costs in the $5,000-$15,000 range. Internal conversions of basements/attics are the fastest pathway. ADUs may not be sold separately from the primary dwelling unless created as condominiums under Oregon condo statutes.
Building an ADU without a permit is enforced by BDS as a building/zoning violation under PCC 24.10 and 33.700, with stop-work orders and double-fee retroactive permits, plus civil fines starting at $250/day. ADUs exceeding size or height limits must be modified or removed. Short-term rental of an ADU without an STR permit is a separate violation under PCC 33.207.080.
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Side-by-side rule comparisons with other cities in Multnomah County.
See how other cities in Multnomah County handle adu rules.
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