When Jason Ro and Zac Rockett of Ro | Rockett Design began plotting an addition to a 1950s bungalow in Manhattan Beach, California, their objective was clear: It would be a development project, plain and simple. But as the renovation morphed into a ground-up rebuild—the young architecture firm’s first—a light bulb went off, and Jason and his wife, Sarah, realized it could be the perfect home for the two of them and their growing family. After all, it had everything they were looking for: modern lines, abundant light, and space. Set in a quiet, leafy neighborhood about a mile from the beach, it was also close to family.

Friends since their days at Harvard’s Graduate School of Design, the architects had teamed up in 2011 to form Ro | Rockett Design with two offices—Jason in Los Angeles and Zac in San Francisco. Developing the 3,150-square-foot house from scratch gave them the opportunity to stretch their design chops. “We’d seen so many homes with the same floor plan: four corners, with the dining and living rooms in front and the kitchen and family room in back,” Jason explains. “We were interested in pursuing something different.”

First they had to address the site—a long, narrow lot with the neighboring houses set so close you could almost reach out and touch them. After considering an upside-down layout, with the public rooms upstairs and the bedrooms below, Jason and Zac opted for an open plan on the ground floor and the bedrooms upstairs, with natural light coming from a variety of strategically placed openings: clerestories in the kitchen, skylights upstairs, and large custom windows throughout that frame views of the sky and the adjacent residences. As the idea of making it a home for Jason and Sarah became more concrete, the design evolved further: a small office beside the kitchen became a casual eating area, the laundry moved upstairs, and a solid wall replaced a slatted screen that they’d envisioned separating the dining area and staircase.

From the compact entry, the interior opens to a double-height dining/living room. Further amplifying the sense of expansiveness are glass sliders facing the backyard. “If you can get double-height spaces and connect those to skylights, you can drop a lot of light into a situation where you’re building almost lot line to lot line,” Zac says.

The kitchen has a more intimate feel, courtesy of a dropped ceiling that conceals the mechanicals. “We’re always trying to find opportunities to define space within an open plan through means other than walls, whether through the ceiling or the furniture,” Zac explains.

The open plan suits the Ros and their children, Lucas, Noah, and Clara. “You look at it from the outside, and you think, Oh, it’s a box on a box,” says Sarah, who designed the interiors. “But I’d never trade the light and the openness for smaller, more broken-up spaces or a more formal living room.”

She made it clear, however, that having a television smack in the middle of the ground floor was not on her wish list: “I told Jason and Zac I didn’t want a giant TV in my one living space, and I definitely didn’t want it over the fireplace.” Their solution was an automated lift that tucks the TV out of sight in a built-in cabinet—not only does it keep the space streamlined, but it’s an endless source of fascination for the kids and their friends.

The feeling of openness continues upstairs, where a long corridor runs from east to west and, at four feet wide, doubles as an informal gathering area. Even on cloudy days, the 16-foot-long skylight ushers in plenty of light, and with the flip of a switch, panels within it open to provide natural cooling in summer.

When the couple entertain, gatherings inevitably spill out to the backyard. “We wanted to provide enough breathing room on the outside so that it could be a place that would act like an extra great room,” Jason says.

The minimalist design ensures that there’s a place for everything, whether in the kitchen’s pantry and cabinets, the built-ins in the dining area and upstairs hall, or in Sarah’s diminutive office just off the entry. Despite having young children, the Ros didn’t shy away from painting the walls white or including a few top-of-the-line pieces in the mix of furnishings. “Jason and I want to live in a space that makes us feel content,” Sarah says. “We mix and match: There’s stuff from flea markets and iconic pieces that we want to keep for a long time.”

“We don’t sweat it if there’s a crayon mark on one of the Wegner chairs,” she adds. “Instead of living with things I’ll say I’m going to change later, it’s important for us to have good design around us now.”