Uncovering JAPA

Understanding the Motivations and Barriers to ADU Construction

As cities across the country grapple with a crisis of affordable housing, accessory dwelling units (ADUs) have garnered increased attention as opportunities to increase the rental housing stock while helping homeowners offset their own housing costs. There has been significant interest and research into developing permissive regulations to more seamlessly enable ADU construction. But there has been less emphasis placed on exploring why individual homeowners may or may not choose to build an ADU.

In "Exploring Homeowners' Openness to Building Accessory Dwelling Units in the Sacramento Metropolitan Area" (Journal of the American Planning Association, Vol. 89, No. 1), authors Jamey M. B. Volker and Susan Handy share findings from their survey of over 500 single-family homeowners. Their study was designed to uncover the factors motivating or deterring homeowners from building an ADU.

While only 8 percent of respondents reported currently owning an ADU on their lot, the authors estimated based on survey results that between 33.8 percent and 47.2 percent of single-family detached homeowners in the area might be open to building one.

Given its rising home prices, tight housing market, and permissive regulatory environment, Sacramento homeowners face clear incentives to build ADUs for extra income. What then might account for the low rate of adoption?

Of the 460 survey-takers without an ADU, 246 of them affirmed that they do not want one, for reasons ranging from space constraints to privacy concerns to simple disinterest. But for respondents who were potentially open to building an ADU, the survey revealed that cost barriers were most salient.

Most respondents rated construction costs and development fees as the "major obstacles." And while difficulties securing financing was not ranked highly overall as an obstacle, Black and Hispanic respondents noted this as a larger concern than their white counterparts.

For planners interested in seeing ADUs proliferate in their communities, these findings show that changing the regulatory environment is an important piece in a larger puzzle. Ensuring that ADU regulations are permissive, clear, and widely understood could go a long way toward reducing barriers. But cost remains a clear issue, and the authors' disaggregation of the data showed that constraints like obtaining financing may impact homeowners differently along lines of race and income. Addressing these concerns may require more creative, targeted policy and programmatic interventions.

Access additional resources, policy guidance, and exmaples of local plan recommendations and zoning standards through the Accessory Dwelling Units Research KnowledgeBase Collection.

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The Journal of the American Planning Association is the quarterly journal of record for the planning profession. For full access to the JAPA archive, APA members may purchase a discounted digital subscription for $36/year.

Top image: Getty Images E+ JannHuizenga

About the author
Megan McGlinchey is a master of urban planning candidate at Harvard University.

February 16, 2023

By Megan McGlinchey