Like Finns and their saunas or Brits and their follies, Californians are inseparable from their decks. Perhaps we view them as some final expression of manifest destiny, as if to say, We’ve pushed as far west as we can and, as these partly shaded wooden platforms we’ve constructed demonstrate, we’re never leaving. In fact, we’re going to enjoy it as much as we can. Copious sunshine, cool evening breezes, and a single-minded compulsion to grill salmon steaks have enshrined the deck—distinct in the Californian’s mind from a patio, courtyard, or porch—as a part of our cultural character. We spend hours fussing over them and millions of dollars caring for them, and some of our most precious redwood forests have been milled for the sake of their construction. They are our ideal living rooms, and when summer comes—or in those spots where it never leaves—there is scarcely a use for any other part of the house.

Though he was born in Mexico City, San Diego–based designer and developer Sebastian Mariscal has readily absorbed this Californian obsession with deck life. A veteran of the local architecture scene, the 38-year-old Mariscal has designed a pair of identical houses called 2inns (pronounced “twins”) on a La Jolla hillside overlooking the Pacific. The Mariscals moved into one of the 2inns in November 2006; David and Liz Baun now occupy the other. When asked about the concept for his new home, like a good Californian, Mariscal responds, “What I wanted was to create a big deck with a canopy. That was the basic idea.”

Sparing all manner of hardwoods, local and exotic alike, Mariscal opted to make the main level of his house—home of the grand deck, the 2inns’ organizing feature—out of nearly nothing at all. “The three levels of the house are rooted in a particular material,” he says. “The bottom floor is grounded by the cement; the top is made of wood, like the trees; and the middle, where you have the deck, is air.”

On the first floor—site of the main social space, kitchen, and dining area—three of the four walls are formed by a 25-panel retractable glass NanaWall. Sliding on a hidden track and tucked out of sight in a glass storage closet, the NanaWall allows the glassed-in common space to morph into a massive outdoor living room in a matter of minutes. Suddenly, as the house opens up to the enviable Southern California climate, the ocean is no longer an abstraction viewed through a pane of glass from the couch of a climate-controlled interior. Recognizing that the best feature of his house wasn’t necessarily the architecture but what lay miles beyond it, Mariscal designed the 2inns to make their vistas things less seen than experienced.

Stunning views of the Pacific are not reserved solely for the front facade. The effect created in the living room remains surprisingly strong from the back patio, a modestly sized space that includes a fire pit, a barbecue, a light well leading down to the semi-basement, and a steep, grassy hill. “I wanted to achieve something that most houses cannot,” Mariscal explains. “And that was to have a view from the backyard. Most are totally hidden, but here we have a view straight out toward the water, framed by the architecture of the house."

Unexpected moments abound in the 2inns. Take, for example, the earthen alcoves dug into the grass slope. What could be perceived as unintended hollows are in fact benches and seats carved into the hillside, ideal spots for conversation—the Mariscals entertain often—or simply beholding the vast ocean. Once again, architecture helps frame the view.

Up the concrete stairs, in the private spaces of the second floor, the Mariscals’ three diminutive bedrooms sit above the large common room. (“I never want my bedroom to compete with the social spaces of my house,” Mariscal contends.) The modest master bedroom opens onto a triangular sliver of a patio, at the tip of which rests a small ipe seat. Facing north, instead of directly west toward the ocean, the small seat points up the coast, toward La Jolla’s center and the beaches beyond. Clad entirely in that same ipe, the walls of the bedroom flow uninterruptedly into the facade of the house. Only the sliding glass door suggests a separation of the interior and exterior, an effect repeated throughout the house. “It’s like this wooden box was scooped out of the building’s third level, and what was left, the void, has become my bedroom,” Mariscal says.

That scooping, metaphorical or otherwise, was Mariscal’s own doing. His firm, Sebastian Mariscal Studio, is as deeply involved in the construction of its projects as it is in the design. Seeing each house, condo, or hotel through from conception to completion gives Mariscal something he likes and talks a lot about: facts.

“We do about 70 percent of the construction with our crew,” he reports. “Construction is facts. Knowing that I have to build it really affects how I design a building, and being at the job site has been my best education.” Mariscal is not the only one in his firm who resides in their work: “Most of my office lives in the Billboard Lofts,” he says, referring to an apartment building he designed in downtown San Diego. This has helped Mariscal and his colleagues understand the many facets of putting together a house. “Our cycle helps us so much,” he says. “Being builders, we learn how a building reacts in space, and as residents, how it reacts to the process of using it. It’s all more facts.”

Another surprising fact is that each 2inn totals 4,500 square feet. The top floors manage to feel intimate, however, as does the warren of small rooms below. A good portion of that downstairs space is occupied by the garage, a tidy box that houses Mariscal’s Mini Cooper and a welter of sporting equipment belonging to his two children—Mateo, 11, and Olivia, 9—as well as the laundry room, a small bathroom, and an office for his wife, Maricarmen. The biggest space, however, seems to be the domain of Sebastian and his children, and is reserved for some combination of work and play.

A long, narrow, concrete-floored room runs the length of the house, commencing with a huge sliding glass door that opens onto the grassy front yard separating the house from the street and ending with a small courtyard that looks up to the back patio above. In between is an admixture of playroom and home architecture office, where Hannah Montana, in all her bright pink finery, holds court alongside a low Eames elliptical table, and Olivia and Mateo’s matching iMacs carve out their own space among a jumble of architecture books. A piano, a pair of worn leather chairs, a massive flat-screen TV, a bookcase, and a prototype for a minimalist child’s chair round out the space, giving it the feel of a slick bachelor pad inhabited by a pair of grade-schoolers.

Though Mariscal may not have total control over his office space, he’s loath to leave it. When I ask him if he aims to move into his next architectural project, he doesn’t rule it out, but says that his family is very happy here. They like the easy, expansive, urban life it affords, “within walking distance of the restaurants and life of the village [La Jolla].” He quickly adds, “I also love that the high school is just across the street. No one will ever buy or change that land. My view is perfectly secure.” And so, it seems, are this pair of houses, this pair of decks, and this small group of Californians.