The art of the living roof
Plant a rooftop; change your life. That’s Pamela Berstler’s mission. By converting traditional heat-generating roofs into energy-saving ecosystems where succulents and wildflowers flourish, the West Los Angeles landscape designer hopes to transform the local landscape, one green roof at a time.
“It’s easy to treat this as a fad, or a trend, but this is what our future looks like,” Berstler says. Partnered with her husband, Alex Stevens, in Flower to the People, Berstler designs green roofs for residential clients. She believes homeowners should emulate the green building industry and plant eco-friendly rooftops that absorb and filter storm water, cool or insulate their surroundings and put oxygen back into the atmosphere.
“Green roofs are artful, but they should also be part of a water-management system in the landscape,” she says. And among its many benefits, an energy-efficient “living roof” can be beautiful to look at.
Planted roofs are widely used in Europe and even in some American cities such as Chicago, which has spent the last decade encouraging commercial and residential homeowners to mitigate high energy costs with green roofs. Pasadena recently included green roofs in its mandatory green building policies for new municipal buildings.
But most residential rooftops here are still sheltered by such traditional materials as tile, shingles and composite sheeting. Homeowners haven’t joined the green roof revolution, in part because of structural logistics and expense, experts say.
“The bottom line is that green roofs can make Los Angeles a much better, more livable city,” says Steven Peck, founder and president of Green Roofs for Healthy Cities, a Toronto-based nonprofit membership association for the green roof industry. “But we’re not talking about a technology where you can go to Home Depot and do it yourself.”
After reading about green roofs in a home design magazine, Susan Jenkins and Rene Maza of Altadena wanted to convert an ordinary patio roof into a planted garden-in-the-sky. “But it’s not possible for individuals to do it by themselves,” says Jenkins, director of exhibition management at L.A.'s Museum of Contemporary Art. “We needed both a building contractor and a landscape contractor.”
The couple hired Flower to the People to plant their patio roof with sedums and a wildflower seed mix. Before installing hundreds of tiny succulents and sowing flowers such as yarrow, poppy and clarkia, Berstler worked with Doug Kilpatrick of Foothill Construction General Contractor Inc. in La Crescenta to ensure the wood-framed structure could handle a load of wet plants. The contractor reinforced the 15-by-22-foot patio roof so it could support Berstler’s green roof system.
A root barrier and a drainage mat are sandwiched together on top of a one-half-inch layer of pea gravel and waterproof membrane. Metal flashing protects the roof’s framework from moisture. Together this system creates a “tray” in which the succulents are planted.
Green roofs require 4 to 6 inches of space for roots to grow, Berstler says. Rather than using soil, the designer prefers a lightweight medium such as compact moss or a custom planting mixture. The system can be hand-watered during dry spells or irrigated with low-flow water spray heads that produce about one-third the misting of a regular spray head.
Succulents are ideal for green roofs because of their low water requirements and heat-loving characteristics.
Whether randomly planted or arranged in a pattern, these hard-working perennials grow quickly during the first year or two, filling in gaps to hide exposed planting medium or moss beneath.
The result, Berstler says, is like a meadow, rather than a container of individual plants.
Without a green roof, Jenkins and Maza would have had to stare at a huge rectangle of black tar paper from their home. Because of their sloping property, Jenkins says, “we can’t actually see most of our yard from the house, so we gain a lot of visual pleasure from having a garden roof. It makes our garden look finished and feel cooler.”
Traditional sod roofs are an option in more temperate climates, such as the Bay Area. Designers David McCrory and Roger Raiche of San Francisco-based Planet Horticulture recently used a dwarf fescue grass called ‘No-Grow’ for the roof of a client’s backyard dining pavilion in Woodside, in Silicon Valley.
“It was a folly-like take on the Norwegian-style timbered architecture of their home,” McCrory says. “We wanted the look to be wild and unkempt. It doesn’t look like mowed sod.” The thatched-style roof is further enhanced by wind-borne seeds and those dropped by birds using the roof as a suburban habitat, he says.
Similar to Berstler’s method, McCrory and Raiche used a waterproof membrane to protect the dining pavilion, which was constructed from reclaimed old-growth redwood. A custom planting medium that includes coconut coir pith (a sustainable alternative to peat moss) is lightweight but holds moisture and drains well, McCrory says. A micro-spray irrigation system is used during dry months.
To hide pool equipment and trash bins at a Sherman Oaks garden, Marilee Kuhlmann of Comfort Zones Garden Design in Los Angeles suggested the homeowners cover the fenced utility spaces with vegetation.
“I told them a green roof would capture and clean rainwater instead of it hitting the concrete; plus, it reduces the ‘heat island’ effect of reflective heat; and it is a lot more attractive than looking at pool equipment,” she says. Kuhlmann tapped Berstler to consult on the project, which yielded a pair of abundantly planted succulent roofs.
Berstler fabricated planting “pillows” -- 18-inch-square by 4-inch-deep modular sections filled with tightly wrapped moss. She inserted cuttings of aeonium, crassula, echeveria and other succulents into the moss, densely packing them to create a verdant and textural landscape that’s a lot more attractive than a composite roof or exposed equipment. When placed on the slightly sloped roof (which ensures that any precipitation will gently drain rather than leave the roots in standing water), the succulent cushions create a seamless landscape that’s as pretty as a tapestry.
Since the green roofs were completed in 2005, maintenance has been minimal. The designers like to trim the leggy succulent stems and re-insert them into the growing medium, propagating an even fuller design. During extended dry periods, the roofs are hand-watered once or twice monthly.
Peck, of Green Roofs for Healthy Cities, believes that more Los Angeles homeowners will embrace the environmental and aesthetic value of green roofs if there are incentives in place to help them. “There is a public as well as a private benefit to green roofs, but cities need to help bring down their costs,” he says.
Berstler agrees. “It’s a commitment to transform an entire roof, which is why I’m interested in first designing sheds and small outbuildings,” she says.
“When people see small, artful rooftops in a landscape, they can begin to visualize an entire home with a living roof.”
Debra Prinzing is a garden and design writer whose newest book, “Stylish Sheds and Elegant Hideaways,” will be published by Clarkson-Potter in 2008. Please send comments to email@example.com.
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Tips for greening any rooftop
A green roof may be simple in concept, but the weight and moisture of plants overhead require support and drainage, says Pamela Berstler of Flower to the People. She offers these tips:
Preparation: “The structure needs to be turned into something that can carry the weight load of wet plants,” she says. New construction can be engineered to accommodate plants. Existing rooftops (such as a porch, carport or shed roof) may need added support.
“I recommend people first hire a structural engineer or an experienced contractor to check the integrity of a roof before it is planted,” she says.
Planting: To design and plant a green roof incorporating Berstler’s waterproofing and drainage systems, expect to pay $30 to $40 per square foot. There are economies of scale: The price per square foot decreases as the size of the roof increases.
“You should compare it to the per-square-foot cost of landscaping on the ground,” she says.
Up close: For a detailed schematic drawing, visit www.flowertothepeople.com. Click “Exterior Design” and then “California Green Roofs.”
-- Debra Prinzing