A Nightingale Drive home reflects the current trend toward a modern design aesthetic.

Dream homes in Los Angeles have a new blueprint that reflects today's übercasual lifestyle. Though recent custom-built homes may have traditional architectural style on the outside—a grand Tuscan or Mediterranean villa, for instance—the interiors come as a total surprise.

"The lines are starting to get blurred between modern and traditional," says Mauricio Oberfeld, CEO of Dugally Oberfeld, a Bel Air-based luxury-home construction firm. "Traditional homes now have much cleaner modern interiors, which were once perceived as cold." Though this trend varies from project to project, Oberfeld has seen the change firsthand, as he formerly built almost 90 percent traditional homes and 10 percent modern. In LA, that ratio has grown closer to 50/50 in the last five years, with most clients, even those with traditional houses, wanting cleaner, more modern interiors.

This newly streamlined aesthetic is best achieved through simplified—though not necessarily less expensive—interior details. Out of favor are froufrou and palatial flourishes such as heavy wood mantelpieces and dental moldings, marble columns, and gold leaf. Replacing these finishes are lighter, more contemporary architectural elements.

Architects, builders, and designers work toward a balance of styles, because "ultracontemporary can be daunting" to someone building a custom residence, says Oberfeld, noting that many clients are not interested in sterile, minimalist interiors.