“A city is about diversity, so shouldn’t its architecture be, too?” asks 33-year-old architect, developer, and builder Sebastian Mariscal. An architecturally diverse city is exactly what you see in the immediate vicinity of Sebastian’s home on West Date Street in downtown San Diego. Pomo buildings by Rob Wellington Quigley and generic faux Spanish developments sit next to multi-unit buildings by San Diego stalwart Ted Smith and single-family residences like the Mariscals’, which bump up against corporate high-rise hotels such as the Radisson. “I might not like those shopping center buildings you see over there,” Sebastian says, pointing west toward the harbor, “and those people probably don’t like my buildings, but to me, that’s what a city is—we tolerate each other and get along quite well; that’s why I’m here.”

That’s why a lot of people are here. Downtown has seen a construction explosion in the past ten years. In the past three years alone, 32 new residential projects have gone up in the 2.2-square-mile downtown area. In 1975, downtown’s population was estimated to be 11,000; now it numbers upwards of 20,000, and continues to grow. Sebastian may have gotten into the game a bit late, coming to San Diego from his native Mexico City via Barcelona only six years ago, but it was this architectural freedom and opportunity that drew him. Sebastian has always been around architecture, learning the trade through his father, a Mexico City–based architect, and the ideas have been sprouting ever since. “I started my own firm when I was 18,” he explains, “and the first building I did was on top of a mountain for a television station. It was really hard to get all the supplies and all the people to the site, so we built the components of the structure in another city and then loaded everything on trailers and put it together.”

The experience proved to be formative in many ways and has led Sebastian to a unique approach to design and building which has begun to crop up in his structures. “I think people used to be more patient with architecture,” he says. “But we can’t tell people anymore, ‘Hey, the construction on your house is going to last two years.’ It doesn’t make sense for the client and it doesn’t make sense for us, the architects, developers, and builders.

And on an urban site this is particularly important where permits and parking and everything are much more complicated. Wood deliveries, the crane, it gets crazy, and the longer it takes the more it costs. You have to think of time as the enemy—the challenge—and then you can come up with something really interesting.”

With time standing as his opponent, Sebastian put his plan into action with his own home. When Sebastian and his wife/business partner, Maricarmen, bought their 1,550-square-foot plot of land a little over two years ago, their first challenge was clearing the land. “There was this little house on the site and this guy wanted to buy it from us, but we just said, ‘Move it and it’s yours,’ so now someone is living in that little house in Lemon Grove, California, which is pretty cool.”

The next step in the process was the design, and this is where MS-31 (the Mariscals’ design/build firm) spends the most time on a project, because in their method, everything must be perfect right from the start. “You cannot make changes once construction starts,” Sebastian explains. “Building this way is kind of like building cars. Imagine being on a production line and deciding that you want to change the cut of a window mid-production. The whole process is screwed up and goes big-time backwards and the expenses go way up.”

With their house, the Mariscals’ design challenge was to fit everything they needed into a tiny space; they also needed to create two houses on a single lot to make the project work financially. On one 775-square-foot lot is a 2,800-square-foot house that serves as home and office for the Mariscals and their two kids, Mateo (six) and Olivia (four), and on the other 775-square-foot lot is a 2,800-square-foot house that is the home of the Mariscals’ business partner. “The two houses are completely separate,” Sebastian explains. “They don’t share a wall or anything, but because we’re in the middle of the city, I wanted to make it look like one building for continuity.” The Mariscals were able to get enough space by building up and taking advantage of the no-setback regulations downtown, allowing them to utilize the entire lot, all the way to the property line. “Design-wise, we could pretty much do whatever we wanted,” Sebastian says. “The city really allows people to take chances.”

After five months on the table, the design was settled and permits issued. Redwood siding would reflect the historic neighboring houses and provide some context, all load-bearing walls would be placed on the outside to allow for future flexibility inside, and one trombe wall would keep all plumbing issues contained. The next step was to begin the key component to MS-31’s time-saving building technique: shop drawings. “We do very detailed drawings for every part of the house; every single wall gets its own shop drawing. That way, everything can begin at the same time,” Sebastian explains. “When we start laying the foundation, we also start building the walls, cabinets, and tables, as well as ordering all the windows and doors. When we finish the foundation, the walls are also finished and ready to fall right into place.”

Most design/build projects follow a construction sequence of foundation, framing, roofing, and interiors and can take up to nine months. MS-31’s process cuts construction time considerably. This is not as easy as Sebastian makes it sound, as it requires 100 percent perfection with every component and absolutely no change orders—all design elements must be completely predetermined.

“When you make a change in the middle of construction,” Sebastian says, “it always comes with another change—[if] you make the wall bigger, you have to make the window a little bigger, and then the structural elements need to change, and then suddenly you’re building in ten months instead of four.” But if this is done successfully, this process can trim up to three months off the construction time, Sebastian estimates.

MS-31 also aims to simplify the entire procedure and incorporate that simplicity into the design of the structure. For instance, in his house, all nail and screw heads are left exposed and set in a pattern that becomes part of the design. “If I tried to eliminate the heads or to cover them, it would take forever and be more expensive,” Sebastian explains. “Leaving them exposed obviously saves time and money, but they actually look great, too.”

All of this effort put into his family’s home bears out a design philosophy that Sebastian believes is the future of architecture. “In the old castles,” he says, “there was an enemy that wanted to get inside, so a moat was put around the structure and there were long, skinny windows for arrows so they could protect themselves. All of this was an architectural expression of the time. Needs and challenges are specific and are always changing, and architecture has to respond to that. I think architects too often think architecture is just about beauty and art, which it is, but it is also about timing, especially now. You have to give people what they need, so the more you give people, the more they will come to request modern architecture. I’m interested in making architecture something that people need.”

As tiny downtown San Diego continues to grow, architecture is certainly something people need—and the lively group of architects and designers, like Sebastian, that are also acting as developers are looking to shape the future of their city. “Developers don’t care about the city,” Sebastian says, “they care about numbers. Architect/developers need to give them some competition and provide buildings that make financial sense and aesthetic sense,” he continues. “And I’d like to do that. It’s fun to be part of a city under construction.”