‘Suburban infill’: where can second units have a positive impact?

Deirdre Pfeiffer, "Retrofitting suburbia through second units: lessons from the Phoenix region," Journal of Urbanism 8 (2015): 3

Some take-aways: This article examines the viability of retrofitting single-family suburban developments with additional units, a strategy often called ‘suburban infill’. Based on evidence from the Phoenix region—including the attitudes of different residents toward second unit retrofitting—the article develops a three-pronged typology of suburbs, each with its own outlook regarding suburban infill. The first identified suburb type is “new identity”, which are more likely amenable to infill development, and is characterized by moderate income, low-to-moderate poverty with stable rates, family oriented, faster growing and newer (297). The second and third types are “preserve identity” and “threatened identity” communities, and these are typically un-amenable to infill. They are characterized, respectively, by high income and senior oriented with stable rates, or low-to-moderate income with increasing rates. Due to this variance between suburbs, infill development should be carefully considered, or else risks exacerbating tensions at work in some communities. If un-amenable suburbs are to be convinced that infill development would be beneficial, “arguing for second units as a strategy to accommodate the aging of the baby boomers and demand for multigenerational housing” may have the most traction in some areas (298). The article’s final observation concerns regulations and permitting: it finds that amenable suburbs “may not necessarily have more liberal regulations or permitting,” and this warrants research on the potential impacts of liberalization (298). 

Abstract: Planners are encouraging suburban homeowners to build second units to enable housing affordability, walkability, and aging in place. Yet, little is known about the viability of this approach for different types of suburbs. Based on planner interviews and zoning ordinance reviews in the Phoenix region, this article constructs a typology for identifying suburbs potentially amenable to using second units as a tool. Barriers that limit rezoning to allow for second units across the types include restrictive site requirements and fear of rental units. Arguments for aging in place may be more influential than those for housing affordability in leading suburbs in Phoenix and elsewhere to liberalize their regulations.

Full article (requires access)