While nature abhors a vacuum, it’s not much fonder of a hot tub, which tends to grace the landscape with all the élan of a hair-sprouting mole upon a pristine, milky cheek. However, when a client has only two firm requests for his little patch of Eden—easy maintenance and a body-soaking respite for his work-weary limbs—the designer must find a way to marry programmatic needs with aesthetic principles.

“There was a very long pause when I mentioned the spa,” recalls Mark Erman with a laugh. Erman’s schedule as a research analyst for a hedge fund compels him to arrive at the office by 5:30 a.m., and he rarely makes it back to his home in the Noe Valley neighborhood of San Francisco before six in the evening. “But,” he adds, “I think they were intrigued by the challenge.” They being James A. Lord and Roderick Wyllie, two of the part-ners in the San Francisco landscape architecture firm Surfacedesign Inc. “Given the modest budget, we knew we weren’t going to be creating a custom soaking pool,” says Wyllie, a tad wistfully. “But it’s also the kind of thing we love to do—take off-the-shelf materials and make something that feels crafted and personal.”

“The hot tub wasn’t the only challenge,” adds Lord. “In order to maximize every inch, the developer had dug the garden right into the existing grade.” Defined by a 14-foot retaining wall on the north side, a ten-foot wall to the west, and the house itself—a two-flat, four-story elevation that fairly looms over the rear—the yard felt smaller and more constrained than it actually was. “We wanted to find ways of creating movement and life in the garden, and offer Mark a way to experience nature without getting his hands dirty.

Lord and Wyllie—who met years ago at Harvard’s Graduate School of Design and spent time in the offices of George Hargraves, Martha Schwartz, Peter Walker, and Ron Lutsko before setting up their own shop—started by organizing the space into three zones. Working with design associate Moritz Moellers, they expanded a stone patio at the back of the house, where Erman entertains. From there, a path of parallelogram-shaped stone slabs now leads to the middle zone, a bamboo grove underplanted with a dense carpet of mondo grass, self-natural-izing spring bulbs, and hellebores. A diagonal boxwood hedge signals the sybaritic rear zone, where the hot tub is flanked by three Japanese snowdrop trees rising from a field of decomposed granite.

The hot tub, shielded in front by a fixed steel plate, is encased within an 8-foot-square, steel-framed cover made of ecosourced ipe wood. Closed, it looks more like some Donald Judd–inspired garden folly than any lingering relic of fondue-era California. When it’s time for a soak, the cover slides on tracks to become a waterside deck, then travels 40 feet up to the terrace, where it doubles as a buffet table beside the built-in grill. The garden feels private but no longer claustrophobic, with new side and rear fences that conceal the oppressive verticality of the original walls. The designers took variously sized off-the-shelf redwood planks, stained them black, and intermittently canted them inward to create a sense of movement. As evening approaches, lights embedded between the walls and the fence glow through the gaps, softly illuminating the space.

“I got way more than I imagined,” says Erman, who will soon have more time to enjoy his yard, as he anticipates a sabbatical. As promised, the space has a “just add water” simplicity year round—from winter, when the hellebores bloom, to summer, when the snowdrop trees sag with white blossoms and rain petals onto the ground.