Side by side · Oregon

Compare ADU rules across Oregon

Flexible on where you build? The same backyard cottage can be routine in one city and impossible next door. This table puts 25 Oregon cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.

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City	Detached ADU	Attached / internal	Max size	Owner occupancy	Extra parking	Approval
Albany	Allowed	Allowed	900 sq ft (and at least 25 sq ft smaller than the house if the house is 900 sq ft or less)	Not required	None	Permitted use
Ashland	Allowed	Allowed	1,000 sq ft in single-family zones, 500 sq ft in R-2/R-3, 750 sq ft in NM zones; in every case no more than 50% of the house's floor area	Not required	None; Ashland has no off-street automobile parking minimums	Permitted use
Beaverton	Allowed	Allowed	800 sq ft; no cap for a whole-floor conversion of the house	Not required	None; Beaverton has no parking minimums citywide	Permitted use
Bend	Allowed	Allowed	800 sq ft for the first ADU, 500 sq ft for a second (two ADUs allowed per lot); height per base zone (35 ft in UAR/RL/RS/RM-10)	Not required	None	Permitted use
Clackamas County	Allowed	Allowed	900 sq ft in most zones; 500 sq ft in R-2.5 and for garage-top units in VTH	Not required	None in the urban and rural residential zones; 1 space in the Mt. Hood HR and MRR districts	Permitted use
Corvallis	Allowed	Allowed	900 sq ft, or 85% of the primary dwelling's floor area, whichever is less	Not required	None; Corvallis has no off-street parking minimums citywide	Permitted use
Deschutes County	One detached ADU is permitted outright, but only in five rural residential zones and only above a hard acreage floor. DCC 18.116.355(B) allows one ADU on a lot or parcel zoned RR-10 or MUA-10, and DCC 19.92.160(B) does the same in the UAR-10, SR-2 1/2 and WTZ zones governed by Title 19. The lot must be at least two acres, or at least five acres in the unsewered South Deschutes County area between Sunriver and the Klamath County border. ADUs are not available in Exclusive Farm Use, Forest (F-1, F-2) or Open Space and Conservation zones, nor in the unincorporated communities of Tumalo, Terrebonne or Sunriver. The county opted into the state's rural ADU authorization (SB 391, ORS 215.495) with Ord. 2023-014, and applications opened December 1, 2023. DCC 18.116.355(B); DCC 19.92.160(B); DCC 18.60.020 and 18.32.020 (uses permitted outright)Full rules for Deschutes County Ordinance read August 2026	Attached and internal ADUs clear the same zone and acreage gates as detached ones; the code does not distinguish by form. DCC 18.116.355(A)(1) defines an ADU simply as a residential structure used in connection with or auxiliary to a single-family dwelling, and the 100-foot separation standard in (B)(8) is satisfied trivially by an attached or interior unit. The county's ADU Research Checklist publishes a building permit matrix covering six ADU types: Detached, Attached, Interior (Upper Level), Interior (Lower Level), Above Garage and Garage Conversion. New construction is listed for detached and attached units (1 & 2 Family Dwelling permit); interior, above-garage and garage-conversion ADUs appear only in the conversion column (Structural permit). Read the definitional wrinkle before drawing plans: DCC 18.116.355(A)(4) defines the primary single-family dwelling as sharing no common wall with another residence of any type, yet the county's own permit matrix treats attached ADUs as permitted, so confirm an attached design with planning staff. DCC 18.116.355(A)(1), (A)(4), (B)(8); Deschutes County CDD, Accessory Dwelling Unit (ADU) Research Checklist, Building Permit Matrix for ADU Full rules for Deschutes County Ordinance read August 2026	900 sq ft of useable floor area	Not required	None specific to ADUs	Permitted use
Eugene	Allowed	Allowed	800 sq ft or 10% of lot area, whichever is smaller; 600 sq ft on lots under 9,000 sq ft in the Amazon, Fairmount and South University neighborhoods; 25 ft height cap for detached units	Not required	None. Eugene has no minimum off-street parking requirement for any use	Permitted use
Gladstone	Allowed	Allowed	800 sq ft or 75% of the primary dwelling, whichever is less; basement conversions exempt; detached ADUs capped at 26 ft tall	No owner occupancy is required to build an ADU or to rent one on a long-term lease; ORS 197A.425(1)(b)(B) bars Oregon cities of Gladstone's size from imposing one, and Gladstone's code contains no general requirement. The single exception is short-term use: an ADU used as a vacation rental must have a deed restriction recorded in the Clackamas County Clerk's Office, in a form prescribed by the city, requiring that either the primary dwelling or the ADU be owner-occupied for as long as the ADU is used as a vacation rental. That is not a preempted requirement; ORS 197A.425(2) expressly preserves local authority to require owner occupancy when regulating vacation occupancies as defined in ORS 90.100. Gladstone Municipal Code §17.10.030(7)(e)(B); §17.12.030(6)(e)(B); ORS 197A.425(1)(b)(B), (2)Full rules for Gladstone Ordinance read August 2026	None, unless the ADU is used as a vacation rental (then 1 additional off-street space)	Permitted use
Grants Pass	Allowed	Allowed	1,000 sq ft, but a converted whole floor of the house is uncapped; up to 2 ADUs per lot	Not required	None	Permitted use
Gresham	Allowed	Allowed	900 sq ft or 75% of the primary dwelling's floor area, whichever is less	Not required	None	Permitted use
Hillsboro	Allowed	Allowed	750 sq ft maximum, 250 sq ft minimum. A conversion of an entire level of the house (basement, attic or second story) may take the whole floor even if that exceeds 750 sq ft, but not more than 50% of the primary dwelling's total square footage. Height follows the base zone (2 1/2 stories or 35 ft in the R zones).	Not required	None. No off-street parking may be required for an ADU, and city-wide parking maximums cap an ADU at 1 space (Zone A) or 2 spaces (Zone B) if you choose to build any.	Permitted use
Lake Oswego	Allowed	Allowed	800 sq. ft. of gross floor area, plus an extra allowance of up to 200 sq. ft. of circulation area, chimneys and HVAC when converting space in a dwelling that existed on August 2, 2018. A detached ADU is also an accessory structure: height is capped at the lesser of 24 ft. and the roof form of the main house (28 ft. in R-DD), and in R-15, R-10, R-7.5 and R-6 an accessory structure over 18 ft. tall is limited to 600 sq. ft. and may never exceed the footprint of the main house.	Not required	None. No off-street parking space is required for an ADU, and Lake Oswego now sets only maximum parking, not minimums.	Permitted use
McMinnville	Allowed	Allowed	1,000 sq ft, or 50% of the primary dwelling (garage excluded), whichever is less	Not required	None	Permitted use
Medford	Allowed	Allowed	900 sq ft, and no more than 75% of the primary dwelling's gross floor area (50% for conversions of existing space inside the primary dwelling)	Not required	None	Permitted use
Milwaukie	Allowed	Allowed	800 sq ft floor area (attached and detached); detached also capped at 800 sq ft footprint and 25 ft / 2 stories	Not required	None	Permitted use
Oregon City	Allowed	Allowed	800 sq ft, or 60% of the principal dwelling's gross floor area, whichever is less; basement conversions exempt if no new floor area is added. Detached ADU height capped at the greater of 20 ft or the principal dwelling's height	Not required	None. No off-street parking may be required for an ADU (state preemption); driveways, if built, follow OCMC 16.12.035	Permitted use
Portland	Allowed	Allowed	800 sq ft or 75% of the primary dwelling's living area, whichever is less; no size cap for a basement conversion in a house at least 5 years old	Not required	None	Permitted use
Redmond	Allowed	Allowed	900 sq ft for a detached ADU (300 sq ft minimum); height 32 ft in R-1/R-2/R-3/R-3A, 45 ft in R-4/R-5	Not required	None for the ADU itself	Permitted use
Salem	Allowed	Allowed	900 sq ft, or 75% of the main building's gross area, whichever is less; detached units capped at 25 ft tall	Not required	None; Salem has no off-street parking minimums at all, and ADUs are capped at a maximum of 1 space	Permitted use
Scappoose	Allowed	Allowed	800 sq ft, or 50% of the primary dwelling's gross habitable floor area, whichever is less	Not required	None enforceable (the code still prints a 1-space rule, but state law preempts it)	Permitted use
Sherwood	Allowed	Allowed	800 sq ft gross habitable floor area; detached ADU no taller than the house	Not required	None	Permitted use
Springfield	Allowed	Allowed	800 sq ft, or the floor area of the primary dwelling excluding its garage, whichever is less. Height follows the district cap for the primary dwelling: 35 ft in R-1, 50 ft in R-2, no limit in R-3.	Not required	None. Springfield requires no off-street motor vehicle parking for any use citywide, and the suggested 2 spaces for a detached single-unit dwelling expressly exclude the ADU.	Permitted use
Tigard	Allowed	Allowed	800 sq ft and 25 ft tall for a detached ADU; no floor-area cap on attached or internal ADUs	Not required	None	Permitted use
Tualatin	Allowed	Allowed	800 sq ft gross floor area (all ADU types, no exceptions); ADU also bound by the zone's 35 ft maximum structure height, setbacks and lot coverage	Not required	None	Permitted use

Summarized from each city's ordinance text, most recently read August 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.

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Reading the table

Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.

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