The view out the south-facing windows of Maria McVarish’s penthouse-style, loft apartment in San Francisco’s Hayes District might have been the square, prosaic roofs of the buildings across the street. Instead, McVarish enjoys a landscape mimicking the rolling hills of northern California. Low undulating planters jammed with close-planted sedums rise, one after another, to a background of yellow ornamental grass, which most days glows with the backlighting of West Coast sun.

This garden with its singular challenges is the work of Andrea Cochran Landscape Architecture in San Francisco. Solving the demands of site and logistics on this and other commissions has worked well for Cochran, who in 2004 won an asla Design Award of Merit for another garden, this one on the steep slopes of the Pacific Heights neighborhood in San Francisco. The Pacific Heights garden—at least in the form that Cochran designed it—no longer exists. However, both commissions had certain problems in common: difficult site access, a need for innovative screening, a desire to do a lot in a small area, and the fact that all site work had to be done by hand. In both, she had to deal with harsh environments—one sunny and overheated, the other steep and shaded.

A 1979 graduate of the Harvard Graduate School of Design, Cochran was born in New York and grew up in New Jersey. She took her GSD diploma to San Francisco for work she thought would be temporary—and never left. “This is the best place to be a landscape architect,” she says. “People here spend more time outside and are into an inside–outside living concept. They’re sophisticated about landscape architecture. They have a personal and economic investment in developing outside space.”

The roof garden was built in 2002 atop a three-story addition to a 1906 warehouse. The add-on was designed by McVarish, an architect, who also rehabbed the four-story warehouse on Ivy Street in the Hayes District. Although McVarish now lives in the loft, the garden was designed in 2002 for a previous occupant.

In addition to the usual problems of site access and screening, Cochran faced on Ivy Street some common rooftop issues: security from an adjoining roof, weight, wind, sun, heat, desiccation, irrigation, and the limitations of the city’s fire codes.

San Francisco’s fire codes strictly limit the number of people who may gather in an area with only one exit, like the roof garden. Consequently, Cochran needed to reduce usable space on the 1,263-square-foot deck. She did so by filling large areas with 16-foot-long planters, then filling strips between the planters with dark, rounded Mexican beach stones that discourage walking. The pedestrian spaces are organized into three assembly areas. Although the remaining area of the deck looks small, it has proven capable of containing 150 people.

Fire codes also dictated some materials choices; no more than 500 square feet of flammable materials was permitted. Cochran used 481 square feet of Trex decking, a plastic lumber product composed of recycled shopping bags and hardwood scraps. The walkable part of the deck intersperses areas of Trex with strips of aluminum checkerplate and square pedestal pavers. To make the aluminum look less industrial and more in harmony with the Trex decking, the metal sheets were cut into strips like planks and screwed down.

Cochran mitigated weight in the planters by using lightweight volcanic soil, which averages 80 pounds per cubic foot. Even so, she limited the height of the planters in the middle of the deck to 18 inches and had them built of lightweight aluminum. Beneath the planting medium is Styrofoam, cut in waves to follow the shape of the planters. “There’s very little soil here,” she says. A layer of fine, pale-colored granite gravel tops the soil, providing both color and mulch.

Bigger planters, taking advantage of better support at the edges of the roof, host bamboo standing in for trees. There’s room for a small table and chairs on the mini-balcony overhanging the street, more chairs under the polycarbonate sunshade, cantilevered over the deck with cables bolted to the brick wall of the warehouse on the west. Spotlights above the awning illuminate it at night. Besides providing security, Cochran’s acrylic screen on the east side hides ugly piping on the adjoining roof.

A sophisticated touch is a bright line drawn across the deck by a strip lighted at night with fiber-optic cable—a feature that draws the eye across the garden from the window to the edge of the balcony.

Pei-Ying Wei, Cochran’s project manager, found herself faced with enormous logistical problems in building the roof garden. To minimize costs, Wei hired a crane to hoist all the materials up in a single day, trying to organize them to arrive in an order they could be used. Despite careful instructions, she found the materials piled in the middle of the deck where support for weight is least trustworthy. The contractor had to be summoned quickly to move it all to the edges. On the other hand, the featherweight aluminum planters, made to Cochran’s specs by a local metal fabricator, were brought up in the elevator.

Budgeted for $150,000, the job came in “closer to $200,000” because of the cost of the polycarbonate screen and sunshade.

Although she used two dozen varieties of succulents, Cochran achieved a unified look by planting five of the six long planters with one variety per planter. The sixth contains a background of Stipa tenuissima, Mexican feather grass. Cochran’s staff did research in a soil lab to determine which succulents grow best in lightweight, lava-rich soil. Most of the plants are from mail order, Cochran says. “The budget required something that wasn’t so rare as to be unusual and pricey.” Exceptions were made for the rare succulents in the four smaller but taller (2 feet square and 3 feet tall) tapered planters on the east edge of the deck.

Despite harsh growing conditions, the garden has needed minimal maintenance. The planters are fitted with built-in, pop-up microsprinklers, whose tiny sprayheads scarcely rise above the low plantings. A local professional gardener tends the roof plantings every two to eight weeks, depending on the season. McVarish says maintenance hasn’t been costly. “We had to replace one bed due to a parasite infection and another because there was a problem with the irrigation system while I was out of town,” she says.

The Ivy Street garden won a Northern California asla Award in 2003.

Project Credits:
Ivy Street Residence designer: Andrea Cochran (acla@acochran.com)
Property owner: Debra Chalsty.
Design/project manager: Pei-Ying Wang.
Building designer, windscreen fabrication consultant: Maria McVarish.
Metal and acrylic fabrication for windscreen and canopy fence: Lawrence La Bianca.
Aluminum planter fabrication: Lewis Metal Fabrications.
Landscape contractor: Pascual Castillo
Structural engineers for windscreen: Endres Ware.
Photographers: Holly Stewart, Jerry Harpur, J. D. Peterson.

By Marty Carlock

Photography – Holly Stewart