Expanding Affordable Middle Housing Options in Single-Family Neighborhoods

Abstract

Problem, research strategy, and findings

By examining the Residential Infill Project (RIP) in Portland (OR), this study addressed the ongoing debate on single-family zoning reform, focusing on the effectiveness of legalizing middle housing in expanding housing options in single-family neighborhoods. The analysis revealed a substantial increase in the proportion of middle housing in residential developments in single-family zones, from 13.4% before the RIP implementation to 44.7% in the 2 years after RIP’s adoption. Almost 40% of these post-RIP middle housing permit units were replacements for existing homes. Compared with single-family housing developments, middle housing projects were more likely to be in neighborhoods with greater density, better walkability, and lower income. The RIP broadened middle housing accessibility by allowing their development on non-corner lots, at greater distances to the city center, and in medium-density single-family zones. The RIP’s approach to regulating development density and building size significantly reduced the average size of middle housing units in single-family zones to less than half that of single-family homes. Given the strong correlation between home sizes and prices, it seems reasonable to infer that middle housing units have become considerably more affordable since the enactment of the RIP.

Takeaway for practice

Eliminating single-family zoning represents an initial step in expanding housing options in single-family neighborhoods. More comprehensive zoning reforms are essential for meaningful improvements in housing affordability and diversity. Cities must reassess and amend zoning codes, particularly development standards, to foster innovation in middle housing development and encourage developers to build smaller homes to lower housing costs.

Keywords:

• middle housing
• Portland
• Residential Infill Project
• single-family zoning
• upzoning

Acknowledgments

I thank the editor Yan Song and three anonymous reviewers for their valuable comments. The preliminary results of this study were presented at the 2023 Association of Collegiate Schools of Planning (ACSP) Annual Conference in Chicago. I am grateful to the session Chair Rolf Pendall and the session participants for their comments. During the preparation of this article, I used ChatGPT as a copyeditor to check grammar errors and improve language. I reviewed and refined all the edits suggested by the tool before incorporating them into the article.

Supplemental Material

Supplemental data for this article can be found online at https://doi.org/10.1080/01944363.2024.2344628.

Additional information

Notes on contributors

Hongwei Dong

HONGWEI DONG ([email protected]) is a professor in the Department of Geography and City & Regional Planning at California State University, Fresno.