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Small homes go big: Accessory Dwelling Unit (ADU) development soars in Portland

aduSmall housing such as accessory dwelling units (ADUs) are experiencing a dramatic increase in Portland. A new animated video, “Accessory Dwelling Units — Take the First Step” is only the latest collaboration by the City of Portland’s Bureau of Planning and Sustainability, the Oregon State Department of Environmental Quality (DEQ), Metro, and space-efficient housing advocates to harness the momentum and success of ADU development in Portland and share the story with others.  ADUs are additional separate living units on single-family lots and are commonly referred to as granny flats, mother-in-law suites, or backyard cottages. The growth of these types of units now comprise almost a quarter of all new single-dwelling residential permit applications in Portland. Last year alone, the City of Portland received almost six times the number of ADU permit applications than the average number of applications received during the 2000-2009 time period. As it currently stands, there are around 800 completed ADUs in Portland, with more in the pipeline.

This dramatic increase is likely the result of several changes the City of Portland made in 2010 in hopes of facilitating additional development of ADUs.  First, the City waived System Development Charges (SDCs) for a three-year period.  This temporary waiver saved homeowners up to $11,000 in costs when obtaining permits for their ADU.  Second, the City raised the maximum size allowance for ADUs from 33 percent of the living area of the primary unit to 75 percent, but kept a cap of 800 SF for the ADU regardless of primary unit size.  Prior to 2010, about 30 ADUs were built annually in Portland. Recent data from the Bureau of Planning and Sustainability show almost 200 ADU permit applications in 2013.  The consistent annual increase in ADU construction since the 2010 waiver prompted City Council to extend the SDC waiver through June 2016. 

adu kitchenThe benefits of ADUs go beyond housing and lifestyle flexibility, affordability, and infill strategy.  In a 2010 report, the Oregon Department of Environmental Quality compared the environmental benefits of various green building practices and found that surprisingly, reducing the size of a house was the most effective way to reduce both the energy and material-related greenhouse gas impacts of a house.  Recognizing the significant environmental benefits of space-efficient housing such as ADUs, Oregon DEQ, Metro, and the Bureau of Planning and Sustainability have recently supported several initiatives to increase understanding and awareness of ADUs.

In 2012, Oregon DEQ, Metro, and others hired Portland State University’s Survey Research Lab to conduct a survey of ADU owners in Portland, Eugene, and Ashland to learn more about how ADUs were designed, developed, and occupied.  The results of the comprehensive survey helped inform the recently-released video as well as the development of numerous case studies of ADU homeowners.  Additionally, Oregon DEQ, Metro, and the Bureau of Planning and Sustainability are co-sponsoring Portland’s first Accessory Dwelling Unit tour on Sunday June 1, 2014. More information about the upcoming tour and these and other ADU initiatives can be found on