When interior designer Merrill Lyons and Charles Brill, a cofounder of lighting design company Rich Brilliant Willing (RBW), purchased a derelict 1901 three-story brownstone in the Gowanus neighborhood of Brooklyn in 2014, they came into the property well rehearsed in the art of renovating a home. Both graduates of the Rhode Island School of Design, they had bought and gutted a one-bedroom apartment in Manhattan in 2009, two years after they met.

“When I renovated in the East Village, it brought out something in me,” says Lyons, a former athletic footwear designer who at the time had recently left a job at Lacoste. Fortunately, the transition allowed her to discover what may be a hereditary predilection. The daughter of an interior designer and sister of an architect, she found work as an interior design consultant for Studio DB, a design-build company in Manhattan, and later started her own firm, Lyons Studio.

Her husband is likewise a man badly bitten by the renovation bug. Brill’s parents encouraged him at a young age to create, rip apart, and fix things—like his first car, a 1980 Volkswagen Rabbit. “We had to tow it home, and I’d spend evenings repairing the car and welding its gears,” Brill recalls. “My father would come out at night in his underwear and tell me to go to sleep.”

When the couple worked together on the apartment renovation, Lyons fine-tuned an aesthetic that they both liked so much, they decided to revisit and expand the style for the Gowanus town house. Gutting it down to the brick facade, beams, and stair railings, the couple finished the renovation in six months with a budget of $300,000; two months later, their son was born.

Where others may have buckled under pressure, the couple worked seamlessly as collaborators. The process was simple: “Merrill would get fabric and wallpaper samples and present them in a curated fashion. I helped make refinements—like the final tone of a light gray,” says Brill, who refinished the mouldings and panels and worked with his father to build the three-story staircase and install the outdoor deck.

The couple chose to retain a traditional brownstone floor plan, “as opposed to a completely open, modern layout,” Lyons says. Though Brill remained impartial to her lighting choices, “she had specific ideas of where to use RBW designs,” he notes—several of which can be found throughout. Often large statement pieces, the lighting pieces are as emphatic as any of the furnishings in the home and wed nicely with Lyons’s design tendencies. “I like adornment, I like color, I like funky things,” she says. “I love vintage.” She dislikes any kind of uniform period design, whether Victorian or a sleek, monochromatic minimalism; she mixes high with low, and clean, modern lines with 19th century–style mouldings.

The vestibule is a telling snapshot of her warm, appealing, and idiosyncratic style. The walls are partly painted in burnt coral and partly papered in a delicate floral pattern. On the floor are small black and white tiles, arranged to spell out “HELLO.” Paired with an Eames Hang-It-All wall rack, an Akoya pendant by RBW transforms the tiny entryway into a mini urban mudroom.

The living room, by contrast, is an ode to Scandinavian design, furnished with rosewood armchairs and a Danish-style leather sofa that the couple brought over from their previous home. The bright kitchen, too, was designed in reference to Nordic country homes, says Lyons, with a palette of white walls, muted green cabinetry, and gray trim. Hanging above the table is RBW’s airy and versatile Palindrome 6 chandelier, an oversize, Mobius strip–like piece equipped with swiveling light heads. Made with a tubular-steel frame that can be reconfigured, it can also be suspended vertically or horizontally. Down the hall, luxurious materials and finishes make up a dramatic, pocket-size powder room, richly textured with a foliage-patterned Hermès wallpaper and a custom sink of swirling green and midnight blue soapstone.

Upstairs, RBW’s Radient sconces—enlarged white disks backed with bands of LED lighting—illuminate the third-floor landing. The master bedroom mixes antiques, like a Chippendale highboy, with black-and-white bone inlaid nightstands from Anthropologie, all set against a backdrop of white and pale peach paint that covers the walls in bands of color.

In the nursery, a large mural—a gift from illustrator Kale Williams—spans an entire wall. “On one hillside, there’s Brooklyn and a brownstone,” Lyons says. “On another hillside, there’s Toronto, and the trees are Minnesota,” a nod to the couple’s childhood homes.

While Lyons and Brill were designing the house, they seldom argued. When they did, “we fought more about things that are not related to the house,” Lyons says. Questions like, “Should we spend $70 on a boxwood plant?” were debatable points, she continues, but collaboration trumped each small challenge along the way. “Design is like creating a song,” adds Brill. “It’s not one creator of a design. It’s a cumulative result.”