A boom in state policies legalizing backyard housing construction is allowing some families to build multigenerational compounds for grandparents, parents, and grandchildren to all live together on the same property.
Twenty-four states have passed laws meant to enable construction of “accessory dwelling units,” or ADUs: separate housing units attached to or located nearby existing homes. The ADUs might be converted basements, over-the-garage apartments or, frequently, small homes built in backyards. In the past two years alone, 11 states have passed laws allowing ADUs at any single-family home, according to New York University’s Furman Center, plus many more state and local laws are meant to reduce barriers to ADU construction.
Pennsylvania lawmakers are currently considering legislation that would allow homeowners to create ADUs in places that are zoned for single-family houses without having to get special permission. The bill passed the state House in June and is now before a state Senate committee.
While many ADUs are used as rental housing, it’s nearly as common to use ADUs for multigenerational living — often elderly parents moving into their own small home on their adult children’s property, or adult children living in their parents’ yard or above a parents’ garage instead of moving away.
California has led the charge on legalizing ADUs, passing a string of laws over the past decade. Several surveys in the state consistently show that about 3 in 10 ADU owners have a family member living in the unit, while about 4 in 10 rent them to strangers.
As soon as Massachusetts moved to prevent cities from restricting ADUs in 2024, Joel and Oreon Mode — who live on the outskirts of Boston — pitched the idea of building one to their son Carter and his wife, Zoe. What if the Modes built a 900-square-foot house in their backyard and moved into the new home, then sold the big house where Carter had grown up to Carter and Zoe at a steep discount?
The Modes would have a single-story place as they got older, instead of their current home where they have to go upstairs to their bedroom. Their 33-year-old son, who had just had a baby, would get to move out of his nearby apartment into a single-family home at a price he could afford. And the Modes would have more time with their granddaughter.
“Our home … would have gone on the market for about $1 million, which is stupid. It’s just idiotic,” Joel, 67, a special-education teacher, said in an interview. “Selfishly, we’ve got this lovely little granddaughter who we’re gaga over, and we’re very close with Carter and Zoe, and we didn’t like the idea that they would be two hours away,” where they would need to go far from Boston to find a home they could afford.
Carter and Zoe eagerly agreed. The family all share a property now in Sudbury, Mass. Oreon, 67, recently retired from her job as a project manager and has time to care for her granddaughter, which means Carter and Zoe don’t pay for daycare either. “I’ve had my friends go: ‘Aren’t you going to get on each other’s nerves?’” Oreon said. “Yeah, probably, but that’s family. That’s what family does.”
Christopher Lee, the lead designer at the company that built the Modes’ new backyard home, said his firm’s homes cost between $200,000 and $600,000 to build, with most running about $300,000 for a two-bedroom house.
“When we started, it was almost all aging parents moving into people’s backyards,” he said. Lately, he’s started seeing more instances where the younger generation is living in the ADU, often people who were priced out of buying a house when prices surged during the pandemic.
“We’re starting to see people using ADUs as starter homes,” Lee said. “We’ve done a handful now where it’s adult children moving into their parents’ backyard and they’re building a house for them and maybe a spouse and firstborn child. … There’s been some level of acceptance that high prices are here to stay. People are moving on.”
Dohyung Kim, an urban planning professor at Cal Poly Pomona, pointed out that ADUs have been marketed as multigenerational housing long before the recent boom in policies aimed at using these small homes to ease the nationwide housing crunch. After all, the additions have long been called “granny flats” or “mother-in-law suites,” implying relatives moving in. (The homebuilder Lennar, which declined to comment for this piece, calls theirs “next gen,” in a nod toward adult children living at their parents’ homes.)
Zoning rules that only permit one house on a lot made it illegal to build ADUs in much of America for decades, Kim said, and still exist. Often, he said, the towns that passed those rules object to the idea of the ADUs being used as rental housing as opposed to for family members.
“Many people build ADUs and use it as a granny flat. But at the same time, many people built ADUs and rented it out,” Kim said. “The tenants used to be more likely to be low-income people of color. Historically, many cities did not want to see that happen.”
Lindsey Fitzgerald, a sales representative for Coca-Cola, moved into an ADU on her mother’s property in Billerica, Mass., with her boyfriend and child. “When I got pregnant, my mom told us that she would be our childcare while we worked. This made all the sense to build this ADU,” she said. “It’s the cheapest way to build or buy a house right now. The market is so crazy that this is what made sense for our family.”
Fitzgerald said that she can look right through her window into her mom’s house; her toddler son delights in going between the two homes. “As my mom gets older, then I’m also here for her to help her,” she added.
Fitzgerald’s mother, Linda Dahl, was already used to having something of a family compound: Dahl’s sister lives in the other half of her split-level home, and her adult son lives with her in the main house.
Dahl said, with a laugh, that her son wants her to put another ADU in her yard so that he can live there instead. “I probably could.”
Contractor David Giacomin, who works in Maryland, said that nine times out of 10, when he builds ADUs the owner is planning for family to live in them — usually elderly parents, or sometimes adult children. Giacomin used to own a Maryland yoga studio, but he started casting about at age 50 for a new business idea when it shut down during the pandemic.
His business has boomed thanks to a state law requiring all localities to permit ADUs by this fall, including in Rockville and Gaithersburg, cities that formerly banned most ADUs. But other requirements, like mandates to install fire-suppression sprinklers, make it much more costly to build them than he thinks it has to be — and most homeowners struggle to get a mortgage to build one.
“If you put a pencil to it, you’d have to charge so much to get your money back in a reasonable time, that it just doesn’t make sense to have it as a rental,” Giacomin said. He thinks that’s why he’s mostly building for families.
One of his clients, Anne Lao, plans to move into one on her daughter’s property in Silver Spring, Md., next month. Lao and her husband moved from California to live just 10 minutes away from their daughter, but since the death of Lao’s husband, Lao’s daughter encouraged her to be even closer. Lao, 70, wasn’t thrilled at the idea of living in an addition, but she agreed to live in a unit at the end of the driveway, where a detached garage used to be.
“When I’m getting older, and if I need help, it’s just very convenient to be right next to them,” Lao said. “It just gives you a little bit more privacy and independence. They have their privacy also.”
She looks forward to seeing her 9- and 10-year-old grandchildren nonstop. “I’m sure I’m going to have visitors every day.”
The rise in ADUs has opened some people up to the idea who might not have considered intergenerational living before, said Wayne State University urban planning professor Kami Pothukuchi.
“For immigrant groups that have a tradition of living in intergenerational households, where older parents will live with their adult married daughters or sons and their families, that has been common and is still common and really has nothing to do with ADUs,” Pothukuchi said. “But where ADUs are legal — that is certainly something that you’re seeing a lot more, within American families that don’t have this as their immediate tradition of living intergenerationally.”
It’s hard to quantify just how common these family compounds are, she said, because so many ADUs, such as basements and garages, are converted into separate living spaces without permits. “If it’s unpermitted, it’s not counted.”
Because some ADUs are counted as part of the main house and some are counted as their own household in the U.S. Census, it’s hard to parse out a trend in multigenerational households in federal data.
David Garcia, who works on housing policy at Berkeley’s Terner Center for Housing Innovation, said he hopes future research will provide greater clarity.
“Part of the challenge with ADUs is we want them to do a lot of things,“ he said. ”We want them to stabilize families. We want them to create more housing stock. But it’s hard for us to know exactly how much of those goals ADUs are fulfilling without better data.”
Inquirer staff writer Michaelle Bond contributed to this article.
