When most families decide to put down roots, they look for big, accommodating houses with broad stretches of yard. Stroll down Galley Avenue in Toronto’s leafy Roncesvalles neighborhood and you’ll see plenty of homes that fit the bill—tall walls of red brick a century old.

Then there’s the exception: a narrow modernist composition of glass panes and purple brick that slips like a bookmark between two older buildings. This is where Karen White and David MacNaughtan made a new home for themselves and their two boys—a bright three-story abode on a lot narrower than most suburban driveways.

“I was surprised that these guys had picked out this property,” says the house’s designer, Donald Chong. When he first saw it, it held a ramshackle 800-square-foot cottage, the oldest and shakiest building on the street. And the lot was tiny: “Squint and you’d miss it.”

But for White and MacNaughtan it represented opportunity. They’d been living in the area off and on for more than a decade, enjoying its mix of deep-rooted Eastern European families and a growing creative class. When they found the site, they were living in a nearby loft with their first child and thinking about the future with a very specific lifestyle in mind. “We wanted to have a contemporary environment and have room for a family,” White says.

Not only that, but they wanted “to support contemporary architecture and create a community of people that we could build a project with,” she adds. Chong—a friend of a friend—was the first link, a young local designer who was just launching his own architecture practice. White, an interior designer and professor of design history, and MacNaughtan, who works in finance, bonded with Chong on the history of modernism and on hockey. “Karen knew all about Peter Behrens,” says Chong. “On top of that, Dave is a goalie, and so am I.”

With Chong signed on, the couple purchased the Galley Avenue property and faced the test of fitting in a family home. It was just 16 feet wide, with requirements for a three-foot setback on one side; the building code also ruled out windows on the sides of the house. “You couldn’t use an old vernacular style because you wouldn’t be able to bring in enough light,” MacNaughtan says. “We didn’t want to have a dark old Victorian. But we also didn’t want to have a contemporary bowling alley.”

Chong was ready for the challenge. As a new practitioner he appreciated the relative risk the homeowners were taking on him. “This was my first everything,” he says. “They had guts.” But he had a strong pedigree at firms, including local favorites Shim-Sutcliffe Architects, and he’d coedited a book about the possibilities of building homes on Toronto’s patchwork of underused back lanes. “Some of that thinking—a very Jane Jacobs idea of compact living and infill—helped in terms of the scale,” he says.

For the Galley House, Chong conceived a 2,100- square-foot house that takes advantage of the lot’s shape: a volume that’s 32 feet high and 62 feet long, with a series of double-height rooms, with glass on the front, back, and top. Working closely with White and MacNaughtan, he finessed the plan to include a number of custom features, most notably a snaking path of stairways that spiral up and down through the house.

The south-facing entry and living rooms are at street level; from there it’s one step up to the dining room to the north, then five steps down and east to the kitchen, which flows into the back garden. Another stair cuts south up to the second floor, stopping at a spectacular double-height living room. “In the older houses, they all put bedrooms in the front,” Chong says. “We all thought it would be a crime to steal the light for a bedroom, which would only be used later in the day. It was all about being greedy with light.” That space also holds the house’s unusual centerpiece: a winding staircase up to the third-level master suite, showcased behind a huge plane of glass on the front facade.

As construction got under way, the sense of community that White and MacNaughtan were looking for was building up around the project. While wandering the back lane with her young son, Griffin, White met some new neighbors, Antje Bulthaup and Stefan Sybydlo. “They asked me who would be doing our kitchen,” White says. “I thought, I’m an interior designer: I will. But I was worried I wasn’t going to complete it in time. So I went home, checked out their website, and nearly fell over.”

Antje Bulthaup is a scion of the Bulthaup family, who runs the German manufacturer of high-design kitchens. Staying in Toronto to open a showroom, Bulthaup and Sybydlo had decided to settle in Roncesvalles—where the company had been sending many catalogs to the homes of local designers. The Galley House became their first local project, to the delight of Chong, a huge fan of their products.

A white Bulthaup system fits cleanly into the 13-foot-long kitchen at the back of the house, designed by White with slate floors and brushed-steel accents. (The range hood, a soaring column of steel, echoes the wall sconces White had already picked out.) And it’s a fine complement to the rest of the interior, which White—who currently teaches furniture history—has kitted out with oak floors and furniture by Hans Wegner, Eoos, and Toronto designer-manufacturers Speke Klein. The classic work of Wegner is a touchstone: “These are early modernist solutions for compact living,” White says.

White and Chong get excited pointing out the connections between the furniture and the architecture. In the dining room, Chong’s carefully detailed railings have an echo in the joinery of oak and steel in Wegner’s CH322 dining table nearby. And the correspondence isn’t just aesthetic. Chong says he and his clients share the ideals of modern architecture. “When modernism was hatched as an architectural language,” he explains, “it was close to this: making use of tight, urban spaces, trying to pull light in, trying to work with a normative family lifestyle.”

All of those ideas show up in the pale, well-lit interiors, dotted with the boys’ artwork and toys. But the couple’s relationship with Chong and his family also reflects an extended sense of kinship.

As a housewarming gift, Chong commissioned his artist mother-in-law to make White and MacNaughtan a quilt depicting their house, the names of everyone involved, and a message: “The heart transforms the house into a home.” As White puts it, “Building projects are like building a family.”

That sentiment accompanies a broader message about housing. While their home is unique, White and MacNaughtan are demographically middle-of-the-road: a married couple with two kids and a cat. For Chong, that makes their strong commitment to urban living and contemporary design all the more notable. “This is about a family that might have made a flight to the suburbs,” he says. In fact, White points out that while living in a 12-foot-wide house involves some sacrifices (there’s only a small backyard for the boys to run around in), it’s not as tough as you might imagine. “My sister lives in the suburbs with her family,” she says. “Everyone thinks we have this small city house with small rooms—but I’ve measured and we basically have the same room sizes.” Which is a sweet payoff for White’s faith in a simple idea.