Contractors are careful on the roof, but accidents can happen. Heavy, sharp tools can get dropped. Stones, loose screws, or gravel can get stepped on and driven into the membrane. These things can happen during roof installation or when air-handling equipment, etc., gets installed or is worked on during routine maintenance. Some of these accidents can result in a puncture of the roof membrane. GAF set out to compare the two popular heat-weldable membranes, TPO and PVC, together with a range of substrates. So, which roofing materials will give you less worry about punctures? GAF’s research uncovered the answers.
Puncture resistance can happen in a few basic ways. Objects can impact at slow or fast speeds and be sharp or blunt. Single-ply membranes do not have the hard exterior surface or redundant layer, which are normally part of multi-ply systems, so they are sometimes perceived as less resistant to punctures. In an effort to shed some light on puncture resistance, GAF took a look at various TPO membranes from the major roofing manufacturers in 45-, 60-, and 80-mil thicknesses and 36- and 50-mil PVC samples.
GAF tested both low- and high-speed impacts and failure was defined as the force required to penetrate the top membrane layer to expose the scrim. In the low-speed test, thicker TPO was better, and fleece-back was also an improvement. No notable difference between manufacturers was found. PVC appears equivalent, except for the 36mil material. Being reinforced with a heavier weight fabric, it showed better performance, highlighting the importance of scrim in this low-speed test.
In the high-speed test, the TPO membranes again indicate that thicker is more puncture resistant with little differences between membranes of the same thickness from all manufacturers. The 50-mil PVC samples were slightly less puncture resistant than 45-mil TPO. One surprise was the poor result of the 36-mil PVC sample (even though it did well in the low-speed test), suggesting that the dense scrim in that membrane does not help resist a falling sharp object compared to a standard scrim. As with TPO, supported PVC is more puncture resistant.
It’s important to note that low-speed manual demonstrations done by slowly pushing a pointed object into a membrane are misleading. It’s best to look at approved test methods (rather than relying on a marketing gimmick) to show how roofing membranes hold up to punctures.