Students Walk All Over New Roofing Solution

• By Mark Mitchell
• 11/01/03

University buildings often are home to expensive equipment, which makes watertight, durable roofing a critical issue. When university students are regularly out walking around on the roof, it takes on even more importance.

That's the case at one particular building at the University of North Carolina at Greensboro (UNCG). UNCG, home to 13,000 students, is comprised of 76 buildings on 200 acres. Its beautiful campus includes Georgian architecture set amidst flowering dogwood and magnolia trees. One of these buildings, the Stone Building, is where Interior Design students work in a studio setting. They often go out onto a flat roof over a lower section of the building to paint their models.

The heavy foot traffic -- and the use of paint -- called for a special roofing solution. The answer, provided by the engineering firm Sutton-Kennerly & Associates, was protected membrane roofing (PMR). PMR is also known as "inverted" roofing. Instead of installing insulation under the roofing surface, an extruded polystyrene rigid foam insulation is used on top of the roofing membrane, protecting the membrane from UV degradation (or from paint), thermal shock and the physical abuse of foot traffic.

"We recommended a PMR with concrete pavers that the students could walk on without damaging the roof," says Mark Harris, senior designer at Sutton-Kennerly. "The roof is a concrete pan-joist deck, and we felt very comfortable going with a monolithic rubberized asphalt membrane directly to the slab."

The PMR solution featured on the Stone Building is provided as an assembly from American Hydrotech, Inc. "Given the age of the building, the light weight of the composite ballast panels allowed us to not increase the load at all. The Fabric Reinforced Monolithic Membrane MM6125 from American Hydrotech is durable, has a long life cycle and can be applied directly to the roof slab. Because the membrane is fully bonded to the slab, there is no water migration," Harris says.

Matt Carr, regional sales manager from American Hydrotech, Inc., agrees. "A conventional roofing arrangement can leave the waterproofing membrane vulnerable to extreme temperatures, UV rays and physical abuse from foot traffic," he says. "PMR prevents that, and American Hydrotech's MM6125 membrane has been successfully used worldwide by leading architects, engineers and owners on all types of structures, including in PMR assemblies."

"We were looking for a membrane that would provide excellent waterproofing," Harris concludes. "We also didn't want to have exposed membrane, because of the students working out there. That's why we developed the system that we did."

With PMR, the inverted roof membrane remains at a constant temperature. It doesn't change dramatically with the outdoor temperatures. With Dow STYROFOAM(r) extruded polystyrene rigid foam insulation, the presence of moisture doesn't mean a substantial loss in insulation effectiveness. In addition, the membrane is protected from UV degradation. An added bonus: because of its longer life cycle, a PMR system is more cost effective.