The Midwest Roofing Contractors Association (MRCA) has a reputation for top-notch technical sessions, and its 2010 annual conference in Indianapolis was no exception. A standing-room-only crowd was on hand for the panel on “TPO Long-Term Performance.”
The Midwest Roofing Contractors Association (MRCA) has a
reputation for top-notch technical sessions, and its 2010 annual conference in Indianapolis was no
exception. A standing-room-only crowd was on hand for the panel on “TPO
Long-Term Performance.” Moderated by MRCA’s technical advisor, Rene Dupuis of
SRI Consultants Inc., the panel featured Helene Hardy Pierce of GAF Materials
Corp., Dwayne Wacenske of Firestone Building Products, Tom Taylor of GAF
Materials Corp., and Randall Ober of Carlisle SynTec.
Wacenske concluded the panel discussion by examining
installation practices that affect the performance of both TPO and PVC.
“Installation practices affect the long-term performance of the roofing
system,” he said. “Initially the roof may be fine, but some problems can arise
Hot-air welding of the seams was identified as the most
common source of trouble. Wacenske recommended that test welds be done at least
twice daily - at the start of the day and after lunch - and whenever the
machine is restarted. The most common problem was excessive heat during
welding, which can consume polymer stabilizers. Excess heat can result from the
air temperature being too high as well as the welder speed being too low.
Wacenske noted the ideal welding temperature should be the lowest temperature
that provides good seams at production speeds.
Another common problem is welder drag. “Improper alignment
of the hot-air nozzle can create gouges in the membrane outside of the seam,” said
Wacenske. “The inside edge of the nozzle should be aligned with the edge of the
Probing seams can also lead to problems. “Be careful probing
seams,” he said. “Use a blunt probe. Probes sharpen with use and occasionally
must be dulled.” He urged contractors to keep the tip of the probe horizontal
to avoid causing damage.
Creasing the membrane when it is folded during installation
is another installation error that can lead to problems down the road. “Folding
over the membrane can result in a hard crease and surface cracking,” he
explained. “Membrane can be folded back for applying adhesives or fasteners,
but weight should not be placed on the fold to hold it in place.”
The panel’s entire PowerPoint presentation is available at www.mrca.org.