In Mexico City, fresh air and a quiet stretch of grass can seem like the greatest of luxuries. To secure these things, Alfredo Oropeza and his family head 60 miles south to Cocoyoc. Set amid fertile highlands that, like neighboring Cuernavaca, are bathed in a more or less perpetual spring, the town has attracted city folk since the 15th century, when Moctezuma I built his pre-Columbian version of the Alhambra here.

Architect Joaquin Castillo blends inexpensive materials, the odd splurge, and  a refined modernist sensibility to create an affordable weekend house for brothers Alfredo and Guillermo Oropeza. The facade is a juxtaposition of rough-hewn local stone, smooth concrete, glass, and steel—the material palette used throughout the structure.

Oropeza himself heads a small empire—a culinary one, spanning books, websites, and Al Sabor del Chef, a TV show. But Oropeza doesn’t exactly have the deep pockets of an Aztec emperor. To share the pleasures and costs of his weekend getaway, he invited his brother, Guillermo, and his family to join the undertaking. Together, they had $160,000 to build on the 7,000-square-foot lot inherited from their father.

Oropeza had a simple but clear program for the house. “The living spaces had to be very open—a place for the whole family to be together,” he says. “And the kitchen had to be at the heart of the house, so that I could look out on everything—living room, dining room, and even the garden and pool.”

He wanted a beautiful home, one that offered familial comfort alongside aesthetics—“a clean and simple place” in which his family could break free from the compartmentalization of both space and time that defines city life, where two busy nuclear families rarely find the chance to all be in the same place at the same time. To concretize his vision, Oropeza hired architect Joaquín Castillo, head of the Mexico City–based firm Transepto.

Their partnership was seamless, enabling Castillo to deliver a home that feels roomier than its 2,300 square feet and more luxurious than its price tag. It helped that Oropeza trusted him implicitly. “Basically, we agreed I’d act as if I were building something for myself,” says Castillo. “That gave me the freedom to make the best choices while still keeping costs low.” Castillo also managed construction, helping avoid unhappy surprises.

In terms of budget stretchers, recinto, an inexpensive local volcanic stone, represented Castillo’s masterstroke, one he deploys to varying effect. For the walls downstairs, rough-cut slabs provide a textural richness reminiscent of travertine. For the downstairs floors, a matte finish turns the stone into something resembling slate. Castillo didn’t cut the recinto into small blocks, which is the usual custom. “Instead, he used larger pieces, which makes the material seem more beautiful, more luxurious,” says Oropeza.

Like recinto, the upper story’s concrete shell construction helped keep costs down. Castillo left the concrete raw, both for its compelling texture and to minimize long-term care. It’s an old thrifty trick, but he went one step further, recycling the wooden molds used to pour the concrete. Some have been turned into weathered rafters, providing a softer, natural accent amid all the hard surfaces. Others he cut into eight-inch strips to create floors for the housekeeper’s quarters, located just off the kitchen.

Beyond material choices, Castillo’s design also smuggles in other low-cost luxuries. For example, floor-to-ceiling glass walls slide open so that the house can flow into the garden, and vice versa. In fact, in mild Cocoyoc, the entire lot becomes a single, seamless space that functions like an oversize living room. To maximize the effect, Castillo pushed plantings to the outer walls of the garden to make way for an unbroken stretch of lawn, which doubles as a playground for Guillermo’s daughters, six-year-old Valentina and nine-year-old Camila. In the middle of the action, Castillo has squeezed in a postage-stamp pool, a favorite hangout for Oropeza’s wife, Lorena, and their two-year-old son, Lorenzo. And even as he chops and dices in the kitchen—the home’s nerve center—Oropeza can partake of it all.

Besides amplifying space, Castillo’s design also discreetly defies gravity. He accomplishes this by supporting the upper floor on a slender steel frame, then cutting an unlikely gap of windows where the two stories meet. This sensation of weightlessness is carried into the heart of the house by the glass-sheathed central hall, which knits together the two wings of the L-shaped construction. Downstairs, the two wings flow into one large space. Upstairs, they are discrete units, one for the kids and one for the adults.

Yet, asked to define what is most luxurious about his new home, Oropeza’s answer goes beyond subtleties of design. “In this house, you always feel connected to everyone else. To be all together in one place, to enjoy a long lazy lunch, this is a true luxury.” He adds, “In English, you have a good word for this. It is our ‘haven.'"