When adding new space to an old house, many homeowners try to match the style of what's already there. But Wanjing Ji and her husband, Tianyu Wu, did the opposite.

When they expanded their 1903-built Craftsman-style home in St. Paul, they opted for an ultramodern addition with a 21st-century aesthetic inside and out.

"We didn't want to mimic the Craftsman style," said Ji, who designed their 600-square-foot addition, which includes a new kitchen, a mudroom, a master bedroom and a bathroom at the rear of the existing house.

"We wanted to keep the original as original and add the new as new," she said. "Each is true to its era and style."

The front of the house is traditional with brick and shingles. "From the front there's no change. It fits in pretty well," Ji said. But the flat-roofed addition in back is starkly contemporary in line and style, clad in black and white fiber-cement siding.

Inside, the contrast is just as sharp. Behind the traditional living and dining room with dark woodwork are bright streamlined spaces that would look at home in a brand-new modernist house.

"It's like going into two different homes," said Curt Irmiger, owner of Full Circle Construction, builder of the project.

Ji, a landscape architect with Coen + Partners, did take some design cues from her home's original character.

"There is some consistency," she said, with subtle nods to the Craftsman-era architecture. The new spaces, like the old ones, have built-ins but they're much simpler in style than the original ones. The sliding door between the kitchen and bedroom is natural-hued wood "to recall the old space but simplified," with a floor-to-ceiling mirror on the kitchen side.

She also maintained the home's original flow and circulation pattern, while creating more open space and connection from the front of the house to the back. "The new and old try to talk to each other," she said.

Ji and Wu bought their home in 2014. "It was OK for a two-person house," said Ji. But when they decided to expand their family they also decided it was time to expand their home.

Ji knew exactly what she wanted, down to the smallest details.

"She had a vision and a lot of reference photos," said Irmiger.

Building such a contemporary addition for a vintage home was a change of pace for his firm, he said. "It was a lot of fun. We're so used to going off details of the old house."

But marrying the old and new to create a seamless whole was "challenging structurally," he admitted. "There was nothing easy about it. It was a challenge having a flat roof and mating it to the old house."

The project also required installation of a new steel beam in the kitchen ceiling to support the new structure. The simple minimalist style of the addition required great precision and attention to detail.

"Minimal style is challenging in terms of craftsmanship," Ji said. "With a lot of trim, it's easy to hide imperfections. With crisp lines you notice imperfections."

And, as with many remodeling projects involving very old houses, they encountered "unforeseen details," said Ji. "The electrical system was such a mess. The floors were not level."

Let there be light

Window placement was a key part of the design.

"In this neighborhood, the houses are so close to each other," said Ji. Side windows would look directly at neighboring houses. Instead the addition has two big picture windows to the backyard and four skylights, two in the kitchen and two in the bedroom. "It's an efficient way to introduce light," she said.

A window above the built-in buffet in the dining room used to face the outdoors. Now it looks into the new bedroom, which incorporates a brick wall that originally was an exterior wall. One of the skylights was placed just above that window, bringing light into the dining room.

The bedroom is big enough to accommodate a crib for the couple's infant daughter, who also has a nursery upstairs. There's a built-in desk facing a window in the master bedroom that can double as a changing table.

The new kitchen includes a center island, a window seat overlooking the backyard and even a gravel Zen garden along one inside wall.

The sleek cabinets, by cabinet maker John Blundred, have flat fronts and no visible handles or pulls. The upper cabinets are white, while the lower cabinets are black with a matte finish. Other materials include gray Caesarstone countertops, large-format 24-by-24-inch Terrazzo tile flooring and black appliances.

Just outside the kitchen is a new ipe deck overlooking the backyard. After the addition was completed, Ji and Wu completely relandscaped their backyard, replacing overgrown plants and weeds with sod, gravel and 80 new plants to create a serene setting.

The project cost between $200,000 and $250,000, according to Ji, plus all the landscape labor and expenses that the couple contributed themselves.

It was worth it, said Ji. "It completely changed our life. I didn't like to use the kitchen much before. Now I'm always in the kitchen. I cook more."

Before the pandemic, they also enjoyed entertaining friends in their new space. Since spring, they've come to appreciate other aspects of their improved, enlarged home.

"Fortunately we finished the project before COVID," she said. "Now we are always at home and both doing conference calls. We can be working on different floors so the calls don't interfere."

Kim Palmer • 612-673-4784