Evidence brief: Affordable accessory dwelling units

Innovative housing solutions for households with low incomes and older adults

Due to rising materials and labor costs, many communities have become increasingly unaffordable and unobtainable for people of all ages. Almost 30% of all households — 21% of homeowners and 46% of renters — are defined as being cost-burdened, meaning they spend more than 30% of their income on housing costs.

In addition to being cost-burdened, older adults face challenges in being able to live independently as they age, such as having difficulties navigating their homes. 

These concerns create a need for more housing options to improve access to affordable housing for low-income households and more accessible housing for older adults.

Accessory dwelling units, or ADUs, offer a solution and are becoming an increasingly popular housing option because of their affordability, flexibility and potential for housing stability. 


Read research highlights below and view the full brief, which was written in collaboration with AARP and showcases four Habitat for Humanity affiliates working to implement ADUs in their communities.

What is an ADU?

ADUs, or accessory dwelling units, are independent housing units located on the same lot as a single-family home.

They come in various sizes and configurations  attached or detached from the primary home, above garages, or as basement apartments. ADUs are also called additional dwelling units, in-law suites, secondary units, backyard homes, guest homes, carriage homes, etc.

What are the benefits of ADUs?

Benefits of accessory dwelling units for households with low incomes and older adults include:

  • ADUs increase housing availability by creating additional lower-cost housing units within existing residential lots, increasing the housing supply without the need for new land development. 
  • ADUs can promote housing stability by generating rental income for those living on fixed or limited incomes.
  • ADUs can help older adults remain in their communities and close to support networks. An AARP survey found that among adults 50 or older, 69% would consider living in an ADU to be close to someone but still have their own space, and 68% would build an ADU to house a caregiver to help with daily activities. 

Research findings

Key factors for expanding the supply of accessory dwelling units 

  • Relaxing or removing major policy and zoning regulatory obstacles encourages ADU construction.
  • Waiving impact fees and improving financing options can help homeowners afford to build ADUs. 
  • Providing education, development planning tools, and preapproved ADU designs facilitates broader and more equitable access to ADU development.

See the full evidence brief

View or download the “Affordable accessory dwelling units: Innovative housing solutions for households with low incomes and older adults” report to learn more about the research supporting the development of ADUs and their many uses, potential barriers to constructing them for Black and Latino households, and details about the ADU programs implemented so far by Habitat.