Many accessory dwellings in Portland rent for less than apartments, PSU study finds

More than half of all accessory dwelling units (ADUs) in Portland cost less than the average rent of the city’s one-bedroom apartments, according to a Portland State University study.

The study found that 58 percent of the owners of ADUs – (internal apartments, additions to home or stand-alone cottages on the same lot) – charge about $1,200 or less for rent and utilities; 20 percent charged between $400 and $900; and 78 percent charged $1,500 or less. 

The average one-bedroom apartment in Portland rents for $1,368 a month, according to the website Rent Café.

Funded by PSU’s Institute for Sustainable Solutions (ISS), PSU researchers Matthew Gebhardt and Yael Kidron surveyed 378 ADU owners, renters and residents who answered questions about prices, reasons for living in the units, planned usages for the units, constructing them, and other questions.

Their other findings include:

• Forty-two percent of ADU owners built their units with the idea using them for long-term rentals; while 35 percent built them to house family and friends.
• Forty-one percent of owners reported the size of their ADUs as 500 square feet or smaller (the average studio apartment in Portland is 452 square feet); while 31 percent were 700 square feet or larger (compared to the average one-bedroom apartment size of 639 square feet).
• About a third of owners intended to use their ADUs for short-term rentals but only 26% currently do so.
• Fifty percent of renters choose to live in ADUs because of cost savings; while 41 percent chose the units because of a desirable neighborhood.

ISS Director Robert Liberty said the survey is nationally significant because of the rising number of cities with unaffordable housing that are considering the roles that ADUs might play in increasing the supply of housing and for achieving other social, economic and environmental goals.  

“As the cost of housing continues to soar in Portland and many cities throughout the country, ADUs are providing more access to affordable housing, housing flexible for homeowners to live in them and rent out their primary house and the ability for neighborhoods to be stable,” Liberty said.

ISS is coordinating a broad collaborative effort with governments, businesses, nonprofit groups and PSU faculty and students to help inform homeowners considering building ADUs and to assess their contributions to the city and region’s housing, equity and sustainability goals.