Modest Densification

Modest Densification’s Role in Housing Reform

Housing Affordability Institute’s Modest Densification series highlights how zoning modernization through modest densification can increase housing inventory, affordability, and access.  

What Is Modest Densification? 

Modest densification is the term used to describe when existing zoning controls are altered to increase density without a complete reclassification of the area’s zoning type. As part of broader zoning and housing policy reform efforts, modest densification can make housing more affordable by increasing housing supply, promoting diverse housing options, encouraging mixed-use development, and fostering inclusive communities.

Modest densification strategies aim to allow the creation of missing middle housing as a “by-right” development option.

Modest Densification vs. Rezoning  

Where rezoning changes what is allowed in a community (i.e. R-1, single-family homes on large lots shifted to R-4– Multiple-family District of medium density multi-family and mixed-use projects), modest densification increases what is allowed by right (without a variance). Modest densification allows greater flexibility for local governments and developers without the need for entering the planned unit development (PUD) process. 

Modest Densification Strategies  

Approaches will vary from project to project and from one neighborhood to another, but the various approaches share the same goal: increase housing affordability and access by delivering more housing options at more affordable price points. 

Modest densification strategies include:

  • Increasing the number of housing types, such as allowing duplexes, twin homes, triplexes, townhomes, or fourplexes in areas zoned for single-family housing
  • Allowing Accessory Dwelling Units by-right
  • Increasing building height maximums
  • Reducing setback requirements 
  • Reducing or lifting minimum lot sizes
  • Reducing or eliminating floor area requirements or square footage minimums
  • Lifting of parking mandates
  • Increasing building height maximums
  • Enable lot splits by administrative approvals 
  • Decreasing impervious surface requirements
  • Reduction of park dedication and trail requirements
  • Increased utilization of administrative approvals for “by-right” development

Through modest densification, more housing units can be added to the same area relative to the existing zoning controls, reducing costs and increasing housing supply. 

Public Support for Modest Densification

According to a 2022 Zillow survey of metropolitan residents in the United States, 77 percent of respondents support either allowing ADUs, duplexes or triplexes in residential neighborhoods. Support was strongest with Gen Z and Millennials both at 86 percent, followed by 78 percent of Gen X and 64 percent of Baby Boomers and the Silent Generation.

By 2023, Zillow’s survey showed an increase in support, with 82% of respondents supporting at least one form of new missing middle housing that modest densification would bring to their respective neighborhoods. Across the generations, support for at least one type of new housing from Baby Boomers and the Silent Generation is 69 percent, Gen X is 82 percent, Millennials and Gen Z are both at 91 percent. 

The Minneapolis-St. Paul area closely aligns with the national growth in support. In 2022, 65 percent of respondents favor of ADUs, and 60 percent in favor of duplexes or triplexers in their neighborhoods. 75 percent were in favor of using either approach.  In 2023, support for modest densification in their neighborhoods had grown considerably, with 84 percent supporting at least one approach. 

Modest Densification and Zoning Reform

When included in broader zoning reform efforts, modest densification represents a proactive and effective approach to addressing the housing affordability and access crises. By increasing housing supply, promoting diverse housing options, reducing land use barriers, addressing NIMBYism, reducing construction and development costs, modest densification can make housing more affordable and accessible to a broader range of individuals and families.