5 county-level rules, plus city-specific rules for 3 cities in Multnomah County, Oregon.
Verified from official government sources
ADUs are allowed in unincorporated Multnomah County lands within the Urban Growth Boundary under Oregon HB 2001 (2019). ADUs are NOT allowed outside the Urban Growth Boundary. SDC waiver available with 10-year no-STR commitment. Entire-home STR use of ADUs is prohibited.
Sheds under 200 sq ft and under 10 ft height do not require a structural building permit in unincorporated Multnomah County per ORSC. Zoning code setback and lot coverage requirements still apply. Sheds with electrical/plumbing require trade permits.
Converting a garage to living space in unincorporated Multnomah County requires a building permit. If the result is an independent unit with kitchen and bathroom, it qualifies as an ADU under Zoning Code Chapter 39. Structural upgrades and trade permits required.
Carports in Multnomah County require a building permit and must meet accessory-structure setback and lot coverage rules under MCC 39.4200. Portland regulates carports under PCC 33.110 base zones with 5-ft side/rear setbacks and a 15-ft height limit in R-5/R-7. HOA restrictions and neighborhood design overlays may apply.
Multnomah County follows Oregon's state-leading ADU laws. Tiny homes on foundations qualify as ADUs under ORS 197.312 and Portland PCC 33.205 — up to 800 sq ft, no owner-occupancy or parking requirement per HB 2001 (2019). Tiny houses on wheels (THOWs) are regulated as park-model RVs under ORS 446 and limited to RV parks or as temporary dwellings under Portland PCC 33.296.
3 cities in Multnomah County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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