PVC Roofs - Polyvinyl Chloride

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WHAT IT IS & SOME HISTORY

PVC stands for Polyvinyl Chloride. It is one of the pioneering single-ply roof materials. The first known PVC roofing membrane was produced by a company called Trocal and was installed in Germany in 1966. Within a few short years, Trocal PVC covered millions of square feet all over the world and single-ply roofing was setting the stage for market dominance.

The reason PVC roofs are not hard plastic like PVC pipe, is the presence of plasticizers. Without getting into it too much, plasticizers are chemical components that allow the PVC to be flexible; PVC in its “natural” state is rigid, like PVC pipe. Early on, there were problems with the plasticizers, and PVC roofs would shrink and become brittle after a few years. In one case I observed, the shrinkage was so severe it actually pulled the parapet walls down.

Plasticizers can migrate to adjacent materials. Therefore, it is important that PVC roofing be installed over substrates that are compatible with the PVC material. Migration can occur if the PVC is installed directly over asphalt, or polystyrene insulation with no separator between them. The separators are often referred to as “divorcing” or “separating” boards or sheets. The “board” will be a piece of rigid roof insulation board, not wood, although it can be made from wood particles.

As a side note with regard to PVC plastic (not the roofing material), I read that Alfred Nobel, the guy who invented dynamite and whose money is behind the Nobel Peace Prize, started a company named Dynamit Nobel, whose early years were marked by the production and development of explosives, later ventured into the realm of developing the world’s first PVC pipe, which is probably the most used plumbing product in the USA, if not the world, today.

Enough about the history and composition of PVC roofing membranes; I could go into much greater depth about it but I have a feeling that not many of you reading this actually care, so let’s get on to the information you do care about.

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