PVC and TPO roof membranes differ greatly in their chemical and physical properties. However, they both fall under the category of “thermoplastics”. Both types of roof are bonded together through the use of specialized high temperature hot air guns. This means the repair process for both roof types is very similar. Therefore we have combined the failures and repairs page for these two roofs.
In thermoplastic membranes, seam failure occurs when an overlap has not been properly heat welded together. This is commonly known as a “Cold Weld”. Once properly bonded, a heat welded seam will never separate
Punctures are typically caused by falling branches, snow removal, HVAC Repairmen, or Hail. Inspect around HVAC Units(especially near access doors) and under overhanging trees.
There is an art to properly heat welding the seams of PVC and TPO membranes. If you weld it too hot, the plastic will burn and will not bond properly to the other sheet. If you weld it too cold, then the plastics do not properly melt together and are prone to failure. Cold welds are far more common. The solution is to use a hot-air gun and reheat the plastic membranes so that they melt together forming a waterproof barrier.
Nearly all punctures to a PVC or TPO roof are repaired cleaning the membrane, then heat welding a patch of the same material over the top of the puncture. The heat weld process causes the patch to become one with the rest of the the membrane sheet. The resulting repair is stronger than if the membrane had not been compromised in the first place.