Walking into the 1889 graystone owned by Andy and Tina Wong is like passing through a time warp. Outside, limestone masonry and stained glass windows bring to mind a bygone era. But inside, the house is decidedly modern, from the open floor plan to the smart TVs, speakers, and thermostats.

It’s the result of a year-and-a-half gut rehab project executed by architects Julie Fisher and Rachel Crowl of FC Studio, who transformed the former two-flat into a single-family home for Andy, a consultant, Tina, a pediatrician, and their two daughters, 8 and 5. “Architects are known for creating beautiful, minimalistic spaces, but they don’t function,” says Fisher. “We wanted to combine warm, clean, modern materials in a livable way.”

They started from near scratch, keeping just the front wall and two sides of the original building intact, and extending the rear wall to accommodate a three-story addition. The move also allowed for a larger kitchen, with cabinets by McDuffee Designs. In addition to its convenient breakfast nook, the kitchen offers such culinary perks as wok and fryer built-ins and a giant hood. “The girls do their homework in the nook; we cook, watch TV,” says Tina. “We live in that area.” The window-filled back wall looks out onto a garage rooftop deck and bathes the kitchen and adjoining living room in light.

To create a modern feel for the four-bedroom, five-and-a-half-bath house, Fisher used walnut architectural details throughout and neutral-colored, clean-lined contemporary furniture, adding pops of color with area rugs and throw pillows. “The furnishings were all about durability and comfort,” says Fisher, who chose a sofa from her favorite brand, Bensen, “because they’re not inexpensive, but they’re not precious, either.” Other items that passed the comfort-meets-durability test include the marble-topped coffee table with a geometric walnut base by Brad Ascalon in the living room and the minimalist yet elegant walnut table and chairs by Matthew Hilton in the dining area (both from Design Within Reach).

Additional modern amenities include seven televisions, more than 40 speakers, and multiple mini-fridges throughout the house. There is also a basement guest room—a necessity for the Wongs, who often host family members from out of town—and a top-floor “man cave.” “Andy’s outnumbered, so he wanted it,” laughs Tina.

The man cave includes a bar with an unusual top. It’s inlaid with typewriter keys that spell out names and words within a jumble of letters, a sort of a word hunt (made by Doc Sanjurjo of D2handcraft). But the pièce de résistance is the built-in slide, situated next to the basement stairs, which leads to the playroom in the basement. “We wanted it in a material that didn’t make it look like an afterthought, so we integrated it into the walnut,” Fisher says. “It doesn’t match the pitch of the stairs, because they’re too steep. So it starts flush and then actually rises.”

“Some of our ideas were crazy, but Julie and Rachel never said no,” says Andy. “They just said, ‘Let’s figure out how to make it work.’”