When a young couple tapped interior designer Mona Ross Berman to bring character to their lackluster corner office, neither party expected to dive headfirst into a multiyear overhaul of the Philadelphia home. At the time, the owners hadn’t considered their long-term design dreams for the contemporary abode in Society Hill, but as Berman began injecting her signature blend of warmth and whimsy into the ground-floor work space, a grander vision began to take shape. “Halfway through that room we decided to do the whole house,” recalls Berman, who proceeded to guide her clients through an extensive gut renovation that would transform the property, inside and out.

Berman knows a thing or two about embracing the urge to start fresh. She learned its value firsthand when she pivoted from an early law career to embrace her creative calling—the shift eventually led to the launch her firm, and it certainly equipped her to turn this outdated townhouse into a sophisticated, highly customized retreat with surprises at every turn. Her effortless execution of the office makeover inspired large-scale adjustments throughout the entire home, including a custom-fabricated butler’s pantry and a stunning three-story glass staircase.

A dramatic single-pivot door fronted with marble and brass leads guests from the exterior courtyard into a color-splashed foyer. Berman doesn’t shy away from featuring loud tones—cherry-red lacquer tops a console table with a concave, mirrored face, and more exuberant hues pop from the Joan Miró painting above. A woven leather rug by Holland and Sherry warms up the poured-concrete floor.

“They told me pretty early on that what they wanted was the coolest house in Philadelphia,” says Berman of her clients. “I don’t think you can ask for a better directive.” Her thoughtful interpretation of that instruction resulted in some truly showstopping additions. Amidst the neighborhood’s brick rowhouses and Federal-style architecture, this home announces itself with a Bauhaus-inspired brass front gate. “You enter through several stages,” explains Berman. “When you first walk by, it’s very distinct, but then you keep getting a flavor of what the rest of the house is going to feel and look like when you enter into the courtyard.”

Designing every inch of the property, which stretches over two lots, wasn’t just about bold statement pieces, however. Berman spent time on subtle and often painstaking details tailored to the family’s lifestyle. The rear patio, for example, is equipped with a retractable awning and lined with custom treillage to provide privacy and shelter when the couple entertains. “I really try to think through function as much as possible,” says Berman. The resulting garden space, like the rest of the home, strikes the perfect balance of beauty and utility.

With her firm based in Philly, Berman feels a particular sense of pride about pushing design boundaries in her adopted hometown, and she purposefully enlisted help from craftsmen in the area—most prominently, general contracting firm Shay Construction and custom fabrication company Amuneal Manufacturing Corporation. “Because we’re so close to New York, we don’t always get the attention we deserve,” she notes. “There are a lot of fantastic, local artisans who work all over the world but are based here who are involved in this house, so, that I’m really proud of.”