PVC (polyvinyl chloride), is a type of plastic formed through a gaseous reaction of ethylene with oxygen and hydrochloric acid. This plasticized attributes help strengthen it as a roofing material and can help make the roof more durable and lower maintenance than similar materials. Typically, PVC is used for flat commercial roofing.
PVC for Flat Roofing
PVC comes in a membrane form and is rolled out onto the roof, then adhered to using nails or adhesive. The addition of the plastics to the membrane makes it resistant to punctures and rips and it is also chemical resistant and fairly low maintenance. PVC is also typically heat welded at the seams because seams are the weakest part of a flat roof. Welding helps to seal these areas and keep them watertight. A good PVC roof is lightweight, durable, and will last up to 20 years when properly maintained.
The biggest drawback to using PVC roofing on a flat roof is the fact that it cannot interact with asphalt materials in any way. Some flat roofs have hot asphalt applied on top of the membrane but this cannot be done with PVC roofing. Additionally, PVC roofing comes in different thicknesses. With PVC, thicker is better and often makes the roof more resistant to cracking or splitting. It is important to note that PVC does not perform well in cold conditions. Most PVC membranes can shatter in cold weather, so you will want to use a reinforced PVC membrane. This will help prevent the entire roof from shattering. Shattering can still occur, even when using reinforced PVC. But, it typically will not spread across the roof. You do not get this problem with cold weather in TPO and EPDM membranes.
PVC Repair and Maintenance
PVC formulations differ across manufacturers. This means that some PVC membranes are not compatible with other PVC membranes. You will not be able to weld them together. In some cases, if a manufacturer goes out of business or makes significant formula changes, the membrane you install today may become useless later on. PVC is also not compatible with a lot of peel and stick or self-adhered patching products. A white EPDM or TPO self-adhered patch will typically not adhere properly to a PVC membrane and is not ideal for repairs. The only way to patch a PVC roof is to weld it with compatible PVC. It is also worth considering that PVC shrinks over time, especially when thinking long term. The membrane pulls away from the surrounding walls and outlets on the roof. When welds spilt, you will end up with leaks into the building which can add up to very costly repairs down the road.
Not much is known about PVC and it is not widely promoted in the roofing industry. So it is not among the popular choices for roofing. However, it has many benefits such as being lightweight, chemically impervious, and resistant to tears and punctures. As the benefits and uses of PVC become more known, you will likely start seeing more of it out there as a roofing membrane option.