A growing number of states across the United States have enacted policies legalizing the construction of accessory dwelling units (ADUs), enabling families to create multigenerational living arrangements on single properties. These units, which can take the form of converted basements, garage apartments, or small standalone homes in backyards, are increasingly being used to accommodate elderly parents, adult children, or other relatives seeking proximity to family members.

To date, 24 states have passed legislation permitting ADUs, and in the past two years, 11 states have adopted laws allowing ADUs on all single-family properties. Local governments have also reduced hurdles to construction, facilitating a surge in ADU development. California leads this movement, with numerous communities embracing ADUs as a flexible housing option. Massachusetts, for example, has seen families like the Modes construct 900-square-foot backyard homes to enable grandparents to live near their son’s family, helping to care for grandchildren and foster daily interaction across generations.

While many ADUs serve as rental units, often providing affordable housing options in high-demand urban areas, a significant share is designed specifically for family use. Christopher Lee, lead designer at an ADU construction firm, noted an emerging trend of younger adults using these units as starter homes due to rising housing costs that put traditional homeownership out of reach. Planning experts have long recognized ADUs—also known as granny flats or mother-in-law suites—as a means of supporting multigenerational households, a living arrangement that zoning laws historically limited but which is now seeing increasing acceptance.

Homeowners frequently balance the desire for privacy with the benefits of proximity by residing in either the main residence or the ADU. In Maryland, Anne Lao and others plan to remain close to their children by building ADUs on shared properties, combining convenience with independence. The trend has particular relevance for immigrant families accustomed to multigenerational living, as well as native-born Americans who face affordability challenges in the housing market.

Despite the surge in ADU construction, comprehensive data on the exact scale and impact remains limited due to varying permit practices and census classification methods. Researchers express hope that future data collection will provide clearer insights into how ADUs support family stability and expand the overall housing supply. As demand for flexible and affordable housing solutions continues to grow, ADUs are positioned to play an increasingly important role in addressing these needs nationwide.