Landscape Contractor / Design Build Maintain

NOV 2014

LC/DBM provides landscape contractors with Educational, Imaginative and Practical information about their business, their employees, their machines and their projects.

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24 LC DBM Minneapolis, has been involved in more than 300 green roof projects over the past ten years. "Intensive and semi-intensive installations (with deeper growing media) are less com- mon than extensive," Durhman says. "But almost all those projects go to landscapers. The more landscaping there is to be done, the more roofing contractors entrust the work to landscapers." "It is common for landscape contractors to install green roofs, but not common enough," says Peter MacDonagh, FASLA, LEED AP, CSLA, owner and director of design and sci- ence, Kestrel Design Group, Inc., a sustainable landscape architectural firm in Minneapolis. "Roofing contractors just do not have the plant knowledge of experienced landscape con- tractors." MacDonagh encourages landscape contractors to seek opportunities in green roof main- tenance. "Building owners and facility managers do not have the necessary expertise to maintain green roofs – reading the rooftop landscape and understanding the micro-cli- mates, identifying and remedying problem areas in the vegetation, preventing costly weed proliferation, monitoring and maintaining green roof irrigation systems, and analyzing and amending the growing medium. Landscape contractors should emphasize their expertise and the benefits of regular maintenance." "More and more green roof project specifications include two- to five-year maintenance requirements," says Durhman. "There will be opportunities for smart, hardworking contractors who can offer cost-effec- tive ways to make building owners lives easier and save them money by taking care of their investments in green roofs," says Molly Meyer, M.S., GRP, founder and owner, Rooftop Green Works, LLC, which installs and maintains green roofs in the Midwest. "Some green roofs, especially intensive installations, require more attention than others, but all of them Green Roof Types A green roof is a supplemental roof- ing system that covers a conventional roof with a waterproofng layer, a root barrier, a drainage system, a growing medium for the plants and a layer of vegetation. There are two basic types of green roofs. • "Intensive" green roofs have six or more inches of growing medium. Because of their weight, about 40 to 300 psf fully saturated, they are only appropriate for structures with high load bearing capacity. Their depth maximizes stormwater retention capacity and allows for a wide range of plants, including turf grasses, fow - ering ornamentals, shrubs, and even trees. Intensive green roofs have to be maintained like gardens at grade. • "Extensive" green roofs are typically two to four inches deep, are less expensive to install, require less maintenance and weigh less. With saturated weights of about 10 to 40 psf, they are suited for large- span structures and retrofts on older buildings. They support a more limited range of plants, including succulents such as commonly used Sedum species, and shallow rooted, dry-climate herbs, grasses, and wild fowers. Green roofs can be "built-in-place," that is, planted up on the roof, or "pre-vegetated;" pre-grown in trays or on mats. Pre-vegetated mats are rolled up, and rolled out, like sod. Xero Flor ( www.xerofora.com) is a pre-vegetated mat system proven in fourishing installations that cover hundreds of millions of square feet around the world. LiveRoof, LLC (www.liveroof.com) manufactures a modular tray system designed with soil-to-soil connection between them to establish an integrated vegetative feld, rooted in a continuous layer of soil extending above and across the tops of the trays. Green Roofs (continued from page 22) Living Roofs, Inc. installed and now maintains this 3,959-square-foot green roof at a vacation home in Lake Toxaway, N.C. The homeowner preferred plants that would complement the autumn colors on the trees around the house so the plant palette includes Sedum spurium and Sedum album. The pre-vegetated, engineered mat system is referred to as "extensive" since it has only two inches of growing medium. "Intensive" installations have more than six inches of growing medium. (See sidebar.) Credit: liverooF, llC

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