Single-Ply Roofs

What are Single-Ply Roofs?

Single ply roofing is available in many of different types of membranes. The three main types are, PVC (polyvinyl chloride), TPO (thermoplastic poly-olefin) and EPDM (ethylene propylene diene monomer) which is discussed separately. ; these roofing types are divided into two classes of polymerbased roofing membranes: thermosets (TS) and thermoplastics (TP). Thermoplastics (PVC and TPO) soften when heated (this process is reversible) but thermosets (EPDM) do not.

PVC and TPO roof membranes are reinforced with polyester or fiber glass reinforcement and feature thermoplastic heat-welded seam technology.

"Thermoplastic" means that when heated sufficiently, the roofing material temporarily changes from a solid to a semisolid state enabling the sheets or panels that are overlapped to be fused or heat-welded together and return to a solid upon cooling, yielding one continuous roof membrane.

PVC is a molecule comprised of carbon, hydrogen and chlorine (taken from salt). First developed in Germany in the 1960s and arrived in North America in the 1970s. Since its inception there have been many improvements over the years, including polyester or fiber glass reinforcement (imparts high tearing and breaking strengths), vinyl resins, ultra-violet light inhibitors, heat-stabilizers, biocides, pigments and plasticizers.

TPO roofing membranes are being marketed as a product that combines the properties of EPDM and PVC, without the associated drawbacks that the latter two materials have. In other words, they are supposed to be as UV-resistant and as heat-resistant as EPDM, and as heat-weldable as PVC.

One point is clear, however: unlike plasticized thermoplastic membranes, TPOs do not contain plasticizers which are added to PVC membranes to increase the flexibility of the product. Therefore, the problem of plasticizer loss associated with some PVC roof membranes is eliminated.