Interest in Accessory Dwelling Units (ADUs)—compact, secondary housing units built on the same lot as a primary home—is surging in some parts of the country, and gaining momentum nationwide. Sometimes referred to as an in-law unit, granny flat, laneway, or sidekick house, ADUs are growing at 9% annually, one recent study suggests, adding 100,000 units each year in the United States. They account for approximately 1.5 million units1 and make up 2% of all U.S. homes—a number that is only expected to rise in the coming decade.
And for good reason: ADUs can help make housing more affordable, support aging in place, and cater to the growing trend of multigenerational living. They can also add up to 35% more value to the larger single family home attached to them, according to the same study. Nonetheless, regulatory requirements and size limitations challenge designers to introduce more innovation, warmth, and functionality to these small, efficient builds. Here are three ADUs that stand out as tiny triumphs, showcasing how wood can be a winning material for small spaces—and proving that less truly can be more.
Bunch Design’s Centrally
Located ADU in Los Angeles
Gives Cottage in the Woods Vibes
The husband and wife duo behind L.A.-based Bunch Design, Bo Sundius and Hisako Ichiki, have carved out a niche when it comes to innovative ADU solutions in the City of Angels. Their bespoke approach integrates new units seamlessly with existing structures, while making the most of limited space and narrow lots. So when it came to designing an ADU for their aging parents, they turned to their own backyard, designing a light-filled, two-bedroom, split-level cottage in which the structural wood is a central feature.
“What’s unique in this project is we eliminated the drywall ceiling to reveal the timber framing, with exposed Douglas fir running the full expanse of the 45-foot long cottage,” Sundius says. To achieve the look, they altered the orientation of the roof joists, running them lengthwise rather than ridge-to-edge. The result is a sculpted wooden ceiling that makes the interior feel both warm and more expansive than its 750 square feet. “So often a home’s framing gets covered up with drywall, but there’s no reason you can’t make it a focal point,” he says. “Without using any additional structure, we created this interesting form. In this case, it’s just good old American dimensional lumber that we’ve turned into a finished material.”
In addition to the vaulted wood ceiling, the unit’s interior features wood floors and a staircase constructed with surfaced-on-four-sides (S4S) dimensional lumber. Clerestory windows, also framed with Douglas fir, draw in light and offer views to an adjacent park.
The home’s exterior is simple, clad in a muted green lap wood siding, with doors and windows painted bright yellow. “All of the houses in the area have a stripped-down Craftsman aesthetic,” Sundius says. “We wanted to play off that iconic profile. It almost resembles a Monopoly piece.”
The project is one of many ADUs by Bunch to rely on simple light-frame construction and exposed wood interiors. “Light-frame timber is uniquely suited to flexible designs, especially for ADUs,” Sundius says. “What we’re doing a little different here, and in other projects, is asking the framers to work as a finish carpenter, and then taking these beautiful framing elements and exposing them.”
Elysian Cottage
Wittman Estes Uses
Prefab Wood Construction
to Create Rentable Seattle Cottage
While in some cases challenging sites call for custom-designed ADUs, there’s also growing interest in replicable solutions that can be prefabricated off site, to pass on savings to homeowners.
That’s the approach Seattle-based architect Matt Wittman of Wittman Estes took when he designed a prefabricated ADU clad in charred cedar and powered entirely by solar energy. The factory-crafted design shows how prefabricated small homes can meet a high-design aesthetic. The unit—designed and built for a homeowner in West Seattle—serves as a one-bedroom backyard unit, which can be rented out or listed on Airbnb.
The client was looking to add an ADU to their property that would not only provide additional rental income but also showcase environmentally sensitive prefab wood construction. The ADU now serves as a prototype for a collection of factory-built models called NODE—a prefab dwelling system originally cofounded by Wittman.
“As a system of components, the entire home can be shipped almost anywhere and assembled in days,” Wittman says. “The project shows that good design can be accessible to anyone.”
The shou sugi ban cedar cladding is treated with a traditional Japanese method of charring wood that not only enhances the visual appeal of the structure but also minimizes maintenance. Complementing the wood, dark gray corrugated metal accents the façade, adding texture and contrast to the overall design.
“We were very focused on coming up with an environmentally sustainable, low-carbon solution,” Wittman says. “It’s constructed using mostly bio-based products and uses very little steel. The structure is all light-framed wood; it uses natural cellulose insulation and charred wood siding.”
Dubbed the Solar Studio, the design is the first detached ADU in Seattle to earn zero energy certification from the International Living Future Institute.
Wittman Estes
Light-Frame, Light-Filled
Portland Granny Flat Has
a Place for Everything
When asked to design a 1,000-square-foot retirement home in the backyard of an existing property in Portland, Oregon, architect Webster Wilson came up with a compact, wood-framed ADU that draws in lots of natural light, uses local materials, and offers innovative storage options.
The solution—designed for a grandmother sharing a property with her daughter and grandchildren—makes the most of its light-frame construction and vertical design. It’s a pared-down, modern take on the Pacific Northwest Craftsman style home, with the familiar gable roof, the intimate backyard scale, and the extensive use of wood complementing the neighborhood’s character.
“I think Portland, in general, is supportive of thoughtful modern design—especially buildings that are well-crafted, site-integrated, and that use regional, natural materials like wood—so I didn’t hesitate to push a more contemporary building,” Wilson said in an interview with Dwell Magazine.
Thin, sleek tight-knot tongue-and-groove horizontal cedar siding and the crisp lines of its standing-seam metal roof give the modest but meticulously detailed structure an elevated, minimalist look. Ample glazing, clerestory windows, and clever second-floor framing—pulled slightly away from the stairs—draws in an abundance of light.
Because constructing the three-story unit required removing an existing garage, Wilson ensured the new design would provide smart built-ins and closets to make up for that loss of storage space and ensure everything has a place. Thoughtful features include a day-lit basement with a bike ramp and exterior entry; a multipurpose main floor for living, dining, and kitchen functions that all open to a garden; and a top floor that multifunctions as a bedroom, an office, and a media room, as well as a small loft space for sleepovers with the grandkids.
Along with its light-frame structure and cedar cladding, the home’s interior features the warmth of exposed wood by way of built-in cedar cabinetry, rift-cut white oak flooring, and a uniquely curved feature wooden handrail.
