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Accessory Dwelling Unit Survey for Portland, Eugene, and Ashland, Oregon

This is a good example of:

Using survey data to determine how accessory housing units are actually used


Accessory Dwelling Units (ADUs) are living quarters that are subordinate to an existing house on a property. ADUs can be detached, attached or contained within the main housing unit (e.g., a basement apartment). Many cities are allowing or pursuing ADUs to increase the number and variety of housing, and to provide family care options.


860 ADUs owned by 839 owners. The breakdown of the 860 total records included 689 from Portland, 104 from Eugene, and 67 from Ashland.  DEQ sent surveys by mail and obtained 290 completed surveys from Portland, 49 completed surveys from Eugene, and 30 completed surveys from Ashland. The survey included questions about past, current, and future ADU use; current occupant demographics and rental logistics; construction; energy use; and owner demographics


Here is a snapshot of answers given to common questions raised regarding ADUs:

How are ADUs used? – 78% used as primary residence for someone other than homeowner; 10% by homeowners for extra space.

How many people live in the ADU? -64% of units are occupied by 1 person while 34% are occupied by 2.  10% of respondents reported children under age 18 living in the ADU.

How many cars do ADU occupants own? – In the three cities, 17% own no car; 62% own one car; 17% own two or three cars. 57% use an off-street space while 37% park on the street.  In the Portland-only results, of the occupants who own a car (77%), 46% park on the street where the city does not require an off-street parking space.

How big are the ADUs? – 39% of units are 600 square feet or smaller; 42% are between 601 and 800 square feet.  57% of units in the survey are detached from the main house.

Do ADU occupants provide services to owners? – 79% of owners reported no services while 10% reported services as part of the deal, mainly lawn and child care.  Another 10% either did not know or did not answer the question.

How much does it cost to build an ADU? 42% reported costs under $80,000 while 17% reported costs between $80,000 and $119,000.  Rents charged ranged from no charge (11% do not charge rent) to $1800 per month.

URL link to Main Resource:

Project Location :

Portland Oregon

Development Context:





Portland State University, Oregon Department of Environmental Quality


  1. So happy to find this site. I have been researching ADUs for the past year (slowly) and bleeive your site will help me reach out to a broader community and find further information.I am currently in my last semester of graduate school at The University of Texas at Austin, getting my M.S. in Community and Regional Planning. I am doing my thesis on Accessory Dwelling Units. Specifically, a program feasibility study for my hometown of Denton, Texas. The thesis will also include 2 case studies that review current programs for ADUs in the country. One of my case study sites is Santa Cruz, CA, I have not decided on the other yet. (maybe Austin’s SMART Housing program). Any suggestions on other cities with successful ADU programs??? I know Portland and Seattle have great programs but I am trying to find a city less urban or west cost. I wish Austin had a stronger program. Darn! Again, so excited to see this site!!Thanks!

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  2. Nadica – I have been looking. You may want to visit the Missing Middle website to see what they have. A guy names Kol Petersen in Portland seems to be on the ADU case as well.

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