Selecting a Single-Ply Membrane

There are several single-ply membranes on the market, and all are fundamentally different products due to their chemistry. They can all be used for long-term warranted installations and will perform for years to come. So how do you choose? What are the differences?

Let's start with EPDM (Ethylene-Propylene-Diene-Terpolymer), a thermoset membrane which is a vulcanized rubber. Membrane splices are completed using adhesive tapes, which means no special equipment is required and the need for power tools is minimized. EPDM is available in traditional black and also in white. Black EPDM has the highest UV resistance of all the single-ply membranes, which means it can take the punishment of higher altitudes or long, sunny summers. EPDM can be used for adhered, mechanically fastened, and ballasted roofing systems. It is well suited for stone ballast installations because of its resilience to stone scuffing and its availability in wider sheets, which means fewer seams.

TPO (Thermoplastic Polyolefin) and PVC (Polyvinyl Chloride) are both thermoplastic membranes but are made from two different chemistries. While very similar, there are significant differences between TPO and PVC that should be considered in the decision-making process. Both membranes are heat-welded at the seams, meaning less chance for water intrusion. Both TPO and PVC are available in standard colors (white, gray, and tan) and also in custom colors.

TPO is very popular in the marketplace and is typically the lowest-cost single-ply membrane. TPO has great reflectivity, which it maintains for a longer period of time than other membranes. TPO can be used for adhered, mechanically fastened, and induction-welded systems and is compatible with pressure-sensitive products. This means on a large job (or even a repair) without easy access to a hot-air welder, the contractor could use pressure-sensitive white EPDM pipe boots or curb wraps in lieu of the TPO versions of those accessories. This also adds flexibility to the product specification.

PVC and KEE HP membranes are both PVC technology – the KEE HP designation means that the PVC membrane is using KEE HP as the plasticizer. KEE HP membrane will remain flexible for a longer period of time than standard PVC. PVC has the highest chemical resistance of all single-ply membranes and is especially resistant to oil, grease, and animal fat. Specifying PVC on projects like airports, food service, and chemical processing is a good decision. Due to the chemistry of PVC, this membrane comes at a greater cost than the other single-ply membranes. When specifying PVC, make sure you pay attention to membrane thickness. Some manufacturers promote thinner membranes to make their PVC less expensive, and compare it to TPO in price and performance. It should be said that the long-term performance of all three membranes is first and foremost about thickness. Thicker is better for long-term weatherability, especially UV resistance.

For more information about all of our membranes, our systems brochure is a good place to start for membrane or assembly selection. For information about EPDM, TPO, PVC, and KEE HP, click on "Roofing Products" at the top of the website drop-downs and make a membrane selection.

If you have any questions, please contact Craig Tyler.