The two hardest-working architects in America aren’t licensed architects—or American-born for that matter. Beat Schenk and Chaewon Kim first gained recognition in 2004 when, in the shadow of the Harvard Design School (Kim’s alma mater), they took a traditional New England worker’s cottage, weather-washed shingles and all, and transformed it into a two-story Cor-Ten steel–and–polycarbonate A-frame (see “New Beginnings,” March 2005). The controversy that ensued only fueled their desire to keep building, and before the rust could set, the young married couple, who met as students at SCI-Arc, decided to expand—not because they wanted to, but because, in their minds, they had to.

“All we could do is build,” says the soft-spoken Kim, 31, a breast-cancer survivor from Korea who has been waiting for a green card for the last five years. “Since legally we cannot take on a commission, we became our own clients, developer, contractor, architect, homeowner, and broker.”

For Schenk, bringing their vision to life was especially significant. “This is my outlet for creativity, for putting out ideas and taking risks,” says the Switzerland native, who spends his days designing hospitals and dormitories for Boston-based Cannon Design. “More importantly, we wanted to show other young architects that, even though the U.S. market is driven by corporations, there is still hope to do something on your own.” So with not a cent to spare, Kim and Schenk went back to the drawing board and began to design what has come to be known as Medium, or the Black Box, a 29-foot-high extension connected to the original Small property (a.k.a. Metal Storage) by a ten-foot-long translucent Polygal corridor. The glue on the model was barely dry when they realized that in order to have two properties on one lot, Cambridge zoning laws required an additional 200 square feet of land.

The logical next step for two broke designers (one employed, the other not) with a dream and a design? Buy the house next door (now dubbed Large, or Grandma’s Shed), which they could only afford by taking out a $560,000 mortgage on Small. “The first banker said, ‘No way you can buy this house with your income,’” says Schenk. “So we found another broker who was, you know...flexible,” Kim continues.

With spending cash at a minimum, the duo made use of their most valuable resource: themselves. “We asked ourselves how we could build with the least amount of capital,” Schenk recalls. They bought every DIY book Home Depot sold, spent hours on the Internet researching cheap materials (cork flooring, Polygal, plywood, leftover marble), and spent weekends and nights doing most of the work themselves. “About 50 percent of the cost is labor,” Schenk says. “So if you can’t install it yourself, you won’t save much.” Money wasn’t the only reason for taking such a hands-on approach. “In the beginning, we didn’t think we would be doing much of the interior finishing work, but I was worried about the quality,” he says. “Unless you pay someone a really large amount of money, if you want it done right, you have to do it yourself.” “And then he winds up in the emergency room,” Kim teases, recalling an incident when Schenk, exhausted from working essentially two jobs, dropped a kitchen knife on his foot. The other two injuries, a swollen ankle and a smashed pinkie toe, were less serious.

The battle scars were worth it. They finished Medium at minimal cost (for the exterior they used inexpensive red cedar tongue-and-groove and stained it black to hide the blemishes) and quickly sold it for $609,000 to Sean and Lynne O’Brien, two health-care professionals who read about the project in the Boston Globe. “We had just moved into the back of an old Victorian in Harvard Square that my wife loved,” says Sean, who convinced Lynne to go to the open house just to take a look. “We went upstairs and saw the bathtub in the middle of the master bedroom. I climbed in, tested it out, and said, ‘Honey, I think we need to buy this house.’ There’s just something about sitting in the tub surrounded by nature in the middle of the city.”

The O’Briens began packing (again) and moved in September 2005. Since then, they have made few modifications, with the exception of the basement, which they finished themselves. “It’s so modern and minimal, we wanted to stay true to their vision,”says Sean. The walls remain white, furniture is sparse, and the cut-away floor-to-ceiling sliding glass doors are unshaded. “At first we were a little scared about buying a place that is so white and light,” Sean says. “But we just learned to become more careful when it comes to our privacy.”

Schenk and Kim kept this in mind when they embarked upon phases three and four of the project. With Medium sold, they were able to take out a second mortgage on Small, allowing them to begin the renovation of Large. “We promised the woman who lived here before that we would give her home a second chance,” Schenk says. “It was a hundred-year-old two-family house stuck in the ’60s and we had to completely start from scratch because nothing was up to code.”

While the first two houses were created with a more conventional setup, for Large the couple decided to flip the program, placing the four bedrooms on the first floor, saving the second story for the kitchen, family, and living room. “The transformation of this house is incredible,” says Peeradorn Kaewlai, a friend of Schenk and Kim’s and Large’s first resident, albeit temporarily. Someone did offer to buy Large, but the designers rejected the offer when the prospective buyers requested too many modifications. “To take a traditional New England home and turn it upside down—well, it will be interesting to observe how the future family who lives here will react.”

The renovations also called for eliminating the attic and knocking down the interior walls, thereby creating a more light-filled and flexible space. To keep on budget, the duo used recycled wood from Small to build the closets and old joists found in the basement to construct the stairs. When it came to painting the exterior, though, they sought outside help. “If you have two things that need to be done, and one is painting the house, the other putting up the plywood, you do the installing because it is the more expensive labor,” Schenk says. “Besides, you can’t really mess up painting a house.”

It’s not the paint job, though, that stops passersby in their tracks, but a sliver of roof that’s missing over the balcony in the front of the house. That too was a victim of circumstance. In order to acquire enough land to build X-Small (yes, there is a fourth house), they had to find yet another tricky solution to Cambridge zoning laws. “If a roof is over a balcony, it counts to the total floor-area ratio,” Schenk says. “So we just took the roof off.”

That done, the couple could focus their attention on the final piece to the design puzzle, X-Small, or What the Hell Is This, three pivoting 16-by-22-foot marine-plywood boxes. “This was the last element coming together in the entire complex, and we didn’t want it to block the views from the other houses, but at the same time we wanted to draw in as much light as possible,” Schenk explains.

Each floor of X-Small has a different look and feel (marble on one floor, oak plywood on the next), but all are connected by the custom-made skylights on the four corners (you can’t be cheap on everything, Kim notes). Keeping the windows to a minimum maximizes the privacy, something that’s all too important when there are four houses on just two lots, especially when the designs draw as much attention as they do.

“One night, I was walking around [Small] in my underwear and I saw someone go by the side of the house,” Kim says. “I almost called the police, but it turned out to be a professor from Harvard checking it out. That’s just one reason I want us to move to X-Small when it’s done.” (The other is to keep their work life separate from their personal life, if that’s at all possible.)

Four years, four mortgages, 16 credit cards, and about $100,000 of debt later, Schenk and Kim are putting the finishing touches on the final phase of their makeshift North Cambridge complex. Most people would relish in the completion and look forward to a little R&R. Not this couple. “We could take a vacation. We haven’t been on one in ten years and we still need to go on a honeymoon,” Schenk says. But they won’t. Instead, they’re in the thick of designing a library for a Swedish competition and looking for another lot to buy. Looking at Kim, Schenk adds, “This is just the beginning.”