Potted banana trees give tropical flair to the courtyard between the house’s entry and the freestanding garage.

A second-floor stair landing may seem like an odd spot to put a home office, but that’s where interior designer Ann Waldman likes to work. The trestle table she uses as a desk is pushed against the wooden balustrade, overlooking the stairs and a periwinkle-blue painting of two frolicking nudes by Portland artist Michele Russo. The light is lovely: a soft glow emanates from a skylight in the recessed ceiling and plays across sand-colored walls, imparting a sense of serenity. Lingering here, it’s hard to imagine a better place to wax creative—an effect that owes a lot to Waldman’s décor, though she humbly credits the home’s good architecture.

"This is a Rose Tarlow house‚" she says. "That’s half the battle, right there."

If you haven’t heard of Tarlow (I hadn’t), she’s a Los Angeles-based furniture manufacturer and decorator whose taste is so legendary, it makes Martha Stewart visibly nervous to be in the same room with her. (You can watch Stewart make awkward, palsy overtures to Tarlow about the proper way to fluff pillows in an easy-to-Google 2001 interview.)

There’s no pat way to describe the Tarlow look, though Pottery Barn has tried hard to imitate it: think antique-reproduction furnishings, flea-market treasures, and romantic touches like strands of ivy climbing the interior walls of a living room. The result—a rare aura of beauty, refinement, and authenticity—is something that Jay Gatsby would have paid a fortune to procure, that Tarlow clients like David Geffen enjoy, and that Waldman thought of when she saw this Southwest Hills home. "It’s elegantly comfortable‚" she says. "In each room, the windows capture light and views of the garden."

Waldman and her husband, James, an ophthalmologist, moved into their house in 2006. Their two children had just graduated from college, and Ann and James were tired of twenty-seven years of climbing stairs in their West Hills abode—the 1970s experiment in hillside living, designed by Portland architect Dale Farr, occupied five cascading levels on three foundations. The couple went house hunting.

The residence they found had once been the carriage house of a grand mansion. The main house, designed by William Christmas Knighton, Oregon’s first official state architect and the creator of the Governor Hotel, was built in 1907 for Maud and Belle Ainsworth, daughters of prominent Portland banker John C. Ainsworth. (A lofty brick Craftsman, it still sits atop the hill.) The Ainsworth family eventually sold the property to Helen and Stephen Eberle Thompson. Helen, a plant enthusiast and lover of fine objects, redecorated the house and created an impressive specimen garden, but old age and declining health eventually forced the couple to give up the main dwelling. In 1983, they hired William J. Hawkins III, a venerable Portland architect, to remodel the two-story carriage house as their retirement home.

"Bill [Hawkins] is old school‚" Waldman says. "What’s important [to him] is the way the human being fits in the space." Using the structure’s original envelope, Hawkins worked out a compact, three-bedroom living space, which emulated the style of Knighton’s main house, with its Craftsman exterior and Colonial Revival interior. He created the wide, shallow living room at the back of the house to showcase Helen’s exquisite Coromandel screen, and to enjoy views of the garden.