For Mark Dixon, an architect, and Alexandra Lange, an architecture critic (and sometime Dwell contributor) and coauthor of the new book Design Research: The Store That Brought Modern Living to American Homes, reuniting the separate levels of a typical mid-19th-century duplexed house common to the Cobble Hill neighborhood of Brooklyn would challenge their expertise and expectations. Their collaboration provided clues as to how their design ideas—his as a designer, hers as a passionate observer—would translate into practice.

Dixon and Lange sought to solve the house’s existing problems and pursue their vision in equal measure. Fortunately, there were opportunities to do both in the same stroke, since restoring original historic features and opening up dark spaces to more light enabled them to introduce new structural and material solutions. Both hoped to deploy beloved design concepts. Lange sought a limited material palette based on the blonde wood of classic Scandinavian design. Dixon translated her desires into surfaces that aren’t typically constructed from wood—ceilings and built-out walls. “I had a lot of front-end ideas about how things should be, but Mark had to work out the reality of it,” says Lange. “We have very similar tastes. We wouldn’t be married otherwise—it’s such a big part of our psyches.”

Inspiring references flashed through Dixon’s mind when he analyzed how to approach the space. A book by woodworker and designer Norman Potter, featuring a small kitchen plugged into an existing space, was among them. The idea of a box within a larger box provided “a lesson in craft and how to take a fresh look at basic functions and rituals,” says Dixon. Also key was Louis I. Kahn’s Yale Center for British Art. “It has a wonderful play of warm and cool materials that was definitely in my mind’s eye when I thought about the palette of materials.”

These inspirations led Dixon to a process of subtraction and insertion. Common to rowhouses of the era, the partially below grade English basement level was murky. An interior wall divided the space awkwardly and was among the first things to go. In its place an open frame of exposed steel beams now projects up through all four levels, adding structural strength with minimal structure. The process of peeling back to essentials extended to the exposed subfloor, which revealed a patinated wood popularly known as pumpkin pine. The front windows, the bottoms of which had been bricked over, were restored to their original to-the-floor height, dramatically increasing the daylight quotient (and reinstating the facade’s original character).

But authentically restoring everything, such as the dark brick walls, was not part of the plan. “We wanted a light-colored material, but not a paint finish—something more like mortar,” says Dixon. “We arrived at pigmented plaster—it’s in the same industrial world as brick. The walls are uniformly light gray but slightly mottled.” The effect hearkens to the claylike color of concrete favored by Kahn, but without the brutal texture, and creates a perceptibly sedate atmosphere throughout the house.

The next step in structural unification came with new staircases. A solid wooden flight, coated with so many layers of red paint so as to approach heavy lacquer, connects the downstairs family area to the parlor floor—an expansive living room defined by ash bookcases set between the steel frame uprights. The remaining flights are fabricated from folded steel with parallel side struts, a design that negates the hefty square tube backbone that supports most metal stairs. The effect is structurally detailed yet light, an exercise in precision by fabricator Wesley Martel, who also removed the heavy hearths of the fireplaces in favor of fine flat fronts.

Dixon’s curiosity about inserting volumes within larger spaces involved approaching the bedrooms and bathrooms essentially as cabinetry. “I was interested in cabinetry wall ideas while working on renovations of similar buildings before we purchased the house.” Like the bookcases in the living room, the built-out walls are framed in ash, constructed more as volumes than slabs. They hide pocket doors in the nursery and guest room and create refined counterpoints to the plaster. The insertion concept extends to an electric and HVAC utility core masked by white acrylic, which, in combination with the exposed steel beams, could seem aggressively industrial but instead nestles along the bookcases almost imperceptibly.

The couple’s combined design ideas find maximum expression in their shared office on the top floor, where the ceiling now crests at one end to an uplifting 10 feet. “It was the serene feeling of being up in the light and the treetops that made us both want the top floor to be the office, but the original ceiling was seven feet high front to back and the whole floor felt like a garret,” says Dixon. Their work areas correspond to their individual personalities and approaches—Lange at an antique desk with just a computer, paper planner, and a notebook, Dixon at a workstation with synthetic stone samples, a large plotter, and other necessary accoutrements of the working architect.

But over the course of this three-year renovation (begun in 2006), with Dixon leading a modest team of workers, came the obligatory low points. The acerbic and amusing analyses of architecture and design for which Lange is best known were caught mute at the often tedious realities of the process. “At several points during the construction I became incredibly frustrated with how long it was taking. I had never experienced it for myself and was used to the sped-up, magazine version of events,” says Lange. “Everything was very emotional, and you’re thinking about the house where you’ll raise then-nonexistent children and live in the rest of your life. You just don’t think of the now.”

There were conflicts over details such as the bookshelves, which in their box-cubby geometry seem far from controversial. “I saw some cool Chinese scroll cabinet somewhere and I proposed something similar, with a lot of tiny slots and a beautiful vertical direction,” recalls Dixon. Lange would have nothing of it: “I thought it was incredibly busy. When I don’t like something I get offended.”

It’s with a tinge of embarrassment that Lange and Dixon now recount the difficulties they encountered and overcame during the remodel. There’s also a sense that the process itself, however challenging to their skills, instincts, and relationship, provided indispensable professional lessons. As they continue on their respective paths of architect and critic, Dixon and Lange can add an important experience to their credentials: client.

Click through the extended slideshow to see more photos from the project.