As a college student, Juniper Tedhams began buying and selling antiques to earn some spending money. This wasn’t a typical side job for someone in her early 20s, but then again, Tedhams wasn’t headed in a traditional direction: She was earning a Master of Fine Arts at the University of Illinois at Chicago, under the tutelage of trailblazing American artist Kerry James Marshall. Although she would become disillusioned with the art world after moving to New York City, her love of antiques persisted, and Tedhams decided to open a shop on the ground floor of the Chelsea townhouse where she lived (and still does).

Her painstakingly curated collection of objects—everything from 16th-century commodes to 1950s Jean Prouvé armchairs—began to attract a circle of established architects, stylists, and designers, including Stephen Sills and his former partner James Huniford. The famous pair befriended Tedhams, slowly but surely nudging her into a career in interior design. “In 2004, they invited me to be in a showroom called the Hamptons Cottage & Garden Idea House,” she recalls. “That really cemented things for me, and shortly afterward I opened my own firm.”

Tedhams used raw Marmorino plaster (finished with beeswax to add a subtle sheen) on the walls of the home’s parlor level. The fireplace, mantel, and mirror, which are original to the house, were paired with a slim custom-designed wooden chandelier and an abstract metal panel made by the designer, who holds a Master of Fine Arts from the University of Illinois at Chicago.

Tedhams was not exactly a novice. She had acquired quite a bit of experience while renovating her own home, a 19th-century townhouse purchased in 1998 with her mother and sister. “It was in really bad shape, filled with a warren of tiny rooms that were once rented out,” says Tedham of the four-story property, which has been repaired and remodeled in various stages over the years. “It was crazy of us to even take it on, yet it forced me to learn about construction and design.” These days, Tedhams and her husband, lighting architect Sean O’Connor, live on the garden and parlor levels of the house, while her sister occupies the top two floors. The home’s ample rooms were decorated with a minimalist sensibility and an eye for diversity. “I’m a very sentimental person, but I’m not sentimental about objects and I don’t like clutter,” says Tedhams, who also has a home in Los Angeles, where her husband’s studio is based. “I love minimalist spaces that also also feel warm and organic.”

Indeed, by mixing a handful of antiques with a selection of midcentury pieces and contemporary wooden furnishings featuring simple lines, she achieved just that. In the living room, for example, a large gilded mirror and an archway with intricate moldings—both original to the house—add some extravagance to an otherwise restrained environment decorated with a rustic sideboard from the 1800s, a glass-and-metal coffee table from the 1960s, and a new rectangular gray sofa. “I’ve lived here for 20 years, and as I continued to fix the house I never wanted it to feel brand-new,” says the designer. “I think that’s part of the reason why there are references to many different time periods.”