Green roofs are typically assembled with stainless steel fasteners, nuts, bolts and washers without any welding, says Cliff Wyatt, Strongwell’s regional sales manager for the southeast United States. Steel had originally been specified for this job, but J.J. Morley decided that using a noncorrosive, lightweight material would be a better choice. Wyatt notes that several green roofs made with steel parts have rusted through within five years of their completion. “You’ve got all your dirt, plants, fertilizers and the water in there every day, and that’s just not conducive to steel,” he says.
Strongwell’s FRP materials offer stronger resistance against the elements than steel. Additionally, the composite materials are less than half the weight of steel, making it easier to install and move the gardens, if needed, for maintenance. Finally, the FRP structures offer life cycle and maintenance advantages. “A question we get a lot is, ‘How long does this material last?’” says Wyatt. “In this case, would 100 years be out of the realm of possibility? Probably not.”
The Gordon Persons Building’s roof is classified as an extensive green roof, meaning it supports 10 to 25 pounds of vegetation per square foot and was designed to be virtually self-sustaining. The large built-in planters are waterproofed with a hot rubberized asphalt system. The Strongwell EXTREN® beams, a pultruded fiberglass-reinforced beam with a thermosetting polyester resin system, and 1 x 1 x 4-inch DURAGRATE® pultruded fiberglass molded gratings create a false bottom so the vegetation trays can be placed throughout the planters. “This reduces the weight in the planters, allows easy access for future planter waterproofing or drain maintenance and allows for simple landscape maintenance and replacement as needed,” says Mark Kelley, vice president of operations at J.J. Morley.
Wyatt says it only took about two weeks to get all of the beams and gratings laid down during the 14-month total renovation project. “The parts are all cut to size and all the holes are pre-drilled, so all [the installers] have to do is lay it out, bolt it together and lay the gratings on top,” he says. Kelley added that the J. J. Morley team was “very satisfied” with the ease of use and outcome of the composite materials.
Composites are slowly but surely finding their way into more architectural projects. “I think [green roofs are] a growing market with a lot of potential,” Wyatt says.