In the beginning, it was personal for Bo Sundius and his wife, Hisako Ichiki, partners of the La Canada, California–based architecture firm Bunch Design. In 2012, when they designed their first in-law suite, or granny flat, it was in their own backyard, and it was for Sundius’s father, who had Alzheimer’s disease. A 720-square-foot one-bedroom they dubbed the Elysian Cottage, the accessory dwelling unit, or ADU, allowed Sundius to help care for his father.
A few years later, in 2017, when California enacted new laws that helped promote the construction of ADUs as a solution to the state’s housing shortage, Sundius and Ichiki embraced the design of in-law suites as a key component of their practice. It was a prophetic decision because ADUs have since boomed in popularity: 23,000 permits were issued in California in 2022, more than quadruple the number in 2017. In-law suites can generate much-needed rental income, but they can also enable intergenerational living, housing parents who can age in place and help with childcare or adult children who aren’t yet financially independent or have disabilities. As Sundius says: “In-law relationships are always better when they have their own kitchen.”
For Sundius and Ichiko, the process of designing a granny flat poses an intriguing challenge: “How do you make something small feel large?,” as Sundius puts it. (In Los Angeles, ADUs are typically limited to 1,200 square feet.) For one, by running clerestory windows across nearly the full span of the structure. “People look to the corners to assess how big a space is, and if those corners have windows, you blur the edges and create a space that feels inherently light,” he says.
For interior bedroom walls, Sundius and Ichiki achieve a similar effect by stopping them short of the ceiling, which is usually vaulted, creating a similar sensation of airiness. And they typically site the ADU so that it offers views not of the main house but of a palm tree in the backyard or the mountains beyond. “Any time you’re recalibrating your eyesight from near to far, you’re getting a sense of distance,” says Sundius. “And so we can make these small spaces feel much larger than they are.”
To create privacy and/or separation, Sundius and Ichiko rely on a couple tricks: using a staircase in a split-level unit as a screen between the kitchen and living room, for instance. Or designing one and a quarter baths: a toilet and sink in one bathroom, which can be used by guests, and a sink, shower, and tub in a second bathroom, a private space for residents.
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Just as Sundius and Ichiko designed an ADU for Sundius’s father, many of their clients were also embracing the intergenerational concept. One homeowner’s parents sold their Long Island home and used part of the proceeds to build an ADU in the backyard of their daughter’s Hollywood house, ultimately splitting their time there and with their son in Hawaii; another client’s parents made a similar move from New York City to the backyard of their son’s property in Los Feliz. Such projects can result in design by committee, with the architects responding to the (sometimes) differing opinions of the homeowners and their in-laws. But the move has clear benefits, including the fact that elder care is no longer a bicoastal conundrum.
Housing a senior resident, of course, requires an accessible design. For Cathy Purple Cherry of Annapolis, Maryland–based Purple Cherry Architects, the mother of an adult son on the Autism spectrum and sibling of a brother with Down syndrome, accessibility underpins all her work. When designing an in-law suite for aging parents, creating an accessible path is essential: doors with widths of two feet ten inches that are wheelchair accessible, for instance, and showers that are flush to the floor. “I know it wants to be sexy,” Cherry says of the swank ADU designs that populate Instagram. But the underlying details of designing a space where a loved one can live their final years—those are anything but.
For her, the process begins with a series of questions. How much separation do her clients want from their in-laws? Will they eventually take over the space? Will the grandparents need to babysit the grandchildren when the clients are on vacation? Some homeowners might want a parent close underfoot, in which case Cherry might design an apartment off the kitchen and buffer it with sound isolation. But most clients prefer some separation, in which case she might site the granny flat off the mudroom hall or over the garage, with elevator access in the entry space. Within the suite itself, Cherry might create a zone of privacy by designing a seven- or eight-foot bump out/sitting area with pocket doors, so Grandpa can stay up late watching TV while Grandma sleeps undisturbed. And if the parents go on vacation? For a suite over a garage, she can design a hallway through the mudroom attic that connects it to the second floor of the house, giving the grandparents easy access to their grandchildren through a set of doors.
Designing an in-law suite for a new build is one thing; designing one next to a house with architectural significance is another. Michael Gooden of Dallas-based M Gooden Design embraced that challenge when a client in Denton, Texas, wanted to add an ADU behind a house designed by Ray Gough, a regional architect who studied under Mies van der Rohe at the Illinois Institute of Technology and was a professor at the University of North Texas. Gooden didn’t want to mimic the existing house, a 1,600-square-foot time capsule of midcentury design, but instead hoped to honor its character and proportions as he pursued a more contemporary approach. The firm designed a one-bedroom, 672-square-foot ADU made of cast-in-place concrete that features clerestory windows and Brazilian cumaru cladding; sliding glass doors open onto a pool and patio, helping blur the boundary between interior and exterior. To save space, Gooden tucked the mechanicals into the ceiling above the bathroom. Permitting took about a year, but the project, completed in 2020, was welcomed by the community. “The city of Denton reached out to me to see if I was interested in partnering with them to streamline the approval process for ADUs,” says Gooden.
Investors have embraced ADUs as income-generating rentals, but what kind of return can homeowners expect for their in-law suite? Numbers can be difficult to pin down, depending on the type and location of the project. Hans and Kristin Struzyna, real estate agents with the Gunderman Group in California’s East Bay, recently compiled the data in Alameda County, which encompasses Oakland and Fremont. Between 2021 and 2023, 712 houses with an ADU were sold for an average purchase price of $1,546,117, as compared to $1,221,397 for houses with a similar lot size but without an ADU. That means that on average, an ADU added nearly $325,000 to the total sales price. But the data also revealed a twist: On average, the houses with an ADU sold for $720 per square foot of liveable space, or $50 per square foot less than houses without an ADU, meaning that the price per square foot decreased as the amount of livable space increased. (Hans Struzyna says this is a common phenomenon: In Alameda, cost per square foot of livable space starts to decline after the first 1,300 square feet.) In other words, multiplying the additional square footage of an ADU by the per-square-foot value of the existing house to calculate the expected return is probably overly optimistic. (Sundius confirms that two ADUs on properties he owns have been appraised at about 75% to 80% of the going per-square-foot rate in the neighborhood.)
Sundius says that the costs of building an ADU almost always penciled out in the past, but rising construction costs and changing code requirements have started to cut into the margins. (Projects that cost $200,000 in 2018, he says, now run $350,000.) Sites that need significant grading or require complicated utility hookups can be prohibitively expensive too. Cherry, for one, has found ways to create efficiencies: by designing an in-law suite bathroom that opens onto a back kitchen and can serve as the pool bathroom during swim season, for instance. And if a client is designing a pool house, Cherry says, going one step further and turning it into an ADU makes financial sense: “All you’ve got to do is put in a bedroom and you’re done.”
Still, in terms of resale, it’s wise not to scrimp too much, says Hans Struzyna, who has noted the rise of the “multigenerational buyer,” particularly over the past year. Many Alameda buyers are looking for an ADU where their parents can live, and if the finishes are too pedestrian, they may look elsewhere. (In Sundius’s experience, better-designed projects also lead to higher rents if the homeowners decide to lease the ADU, which can lead to a higher appraisal.) At the same time, going too high-end in a neighborhood that can’t support the price, Struzyna says, can also be a losing proposition.
Of course, there’s no way to measure the profound impact that granny flats are having on familial dynamics: the chance to spend time with aging parents, say, or give your recent college graduate a launching pad as they embark on a career. They can help solve some pressing problems, help make the American dream more attainable, Sundius says: “I think the ADU is an opportunity to rethink what residential architecture is for another generation.”
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