Jim Stamer, President and co-owner of Prospect Waterproofing Company, serves the Washington/Baltimore metropolitan areas, but what he knows will help serve a nation of roofing contractors.
Since 1992, Prospect has installed millions of square feet of roofing, waterproofing and sheet metal on projects ranging from a few thousand dollars to over $5 million. “I love green roofs,” he said. “Green used to be solely a color, which occurred between blue and yellow in the color spectrum,” he said. “Today, the word ‘green’ is also associated with environmentally friendly practices and products; sustainable design; garden roofing; energy efficiency; and jobs.”
The seminar focused solely on vegetative systems. “In this case, green is green, and white is white,” he said. “Green roofing is nothing new, but green roofing technology has evolved with the use of drainage mediums, other green roofing components and lightweight soils so that plants can survive in minimal soil depths, thereby decreasing the load on the structure.”
Stamer provided examples of green roofs including extensive, semi-intensive, and intensive systems. He cited the importance of aesthetics, but noted the top priority was that the system be watertight. “Owners want long-term warranties,” he said.
According to Stamer, green or garden roofing includes the following:
• Membrane can be most any one that is used for waterproofing, although hot rubberized asphalt, PVC, TPO, and modified bitumen are typical.
• System consists of various layers of insulation, filter fabrics, roof barriers, drainage layers, water retention media, lightweight soil mix, and sedum (plantings).
• System is designed to retain rain water to allow vegetation to absorb it rather than expel water to storm drainage.
• Garden roofs are used to combat heat island effect.
“We do believe the Protected Roofing Membrane Assembly is the best application for a garden roof over a concrete substrate,” he said. “Membrane is adhered to the substrate preventing lateral migration of water should it ever be violated.”
Stamer said the membrane is placed on a heated and cooled substrates, while insulation and ballast are placed over the membrane, protecting it from environmental and most physical abuses. “Ballast is either paver, stone or green roof materials, be it component or modular systems,” he said.
Stamer noted green roofing is typically achieved through two basic methods: self-contained modular systems that are shipped with all required components, including plants; and systems made up of components, including prescribed layers of roof barrier, air layer moisture mat, water retention elements, filter cloth, soil and plants.
“Nobody can transport materials better than a roofer,” Stamer noted.
Lastly, Stamer said maintenance is the key to a successful garden roof. “Success of the plants on the green roof is dependent on routine maintenance,” he said. “Prospect provides that service for the first two years when specified and/or provides a maintenance proposal for the owner’s consideration.”
There was one more benefit of garden roofs Stamer pointed out: money. “That’s one green item that you really need to pay attention to.”