Accessory dwelling units (ADUs) are a valuable tool to help communities broaden housing choice in single-family neighborhoods. In recent decades, many communities have updated their zoning codes to make ADUs a legally permissible use. Despite this trend, ADUs remain a small fraction of the new housing units built in most communities each year.

A new guide from the American Planning Association and AARP is intended to help community leaders, planners, and housing practitioners and advocates take concrete steps to overcome specific barriers to expanding the local supply and legal occupancy of ADUs. Each discussion of potential solutions to a specific challenge includes references to resources that provide supporting information or more extensive guidance.

This guide – called Expanding ADU Development and Occupancy: Solutions for Removing Local Barriers to ADU
Construction – is divided into five chapters. The remainder of this introductory chapter profiles AARP and
APA’s collaborative efforts to promote ADU reforms, provides basic background on the ADU concept,
and introduces four categories of barriers to increasing the construction and occupancy of ADUs across
the United States. The following chapters explore these categories in turn:

• Overcoming Political Barriers discusses how a lack of understanding about ADUs, a lack of inclusivity in planning and decision-making processes, and local intransigence are barriers to ADU reforms and analyzes a range of potential solutions for each.
• Overcoming Regulatory Barriers discusses how a lack of permissible locations, an overreliance on discretionary approvals, and overly restrictive zoning standards are barriers to ADU construction and occupancy and analyzes potential solutions for each.
• Overcoming Procedural Barriers discusses how inexperienced applicants, uncertain processes, and illegal units are barriers to ADU construction and occupancy and analyzes potential solutions for each.
• Overcoming Financial Barriers discusses how planning and design costs, construction costs, and development fees and charges are barriers to ADU construction and occupancy and analyzes potential solutions for each.

The full resource is available here.