THE CHOICE BETWEEN TPO, PVC, or EPDM MEMBRANES

 

The time has come to make a decision on one of your biggest investments, the roof, or more precisely the type of system installed for keeping your structure weatherproof. There are several products on the market that will cover your roof and keep the structure dry but they all have advantages and some disadvantages associated with them. Not all flat roofs are equal. This simple statement’s authenticity needs little in the way of verification if you have ever been on a flat roof. Consultation with roofing professional is the only way to be sure that the system that you decide on, is the best for your structure and budget. With this said, some knowledge in the systems and their associated advantages will go a long way in helping you make an informed decision on this matter.

pvc membrane

Single-Ply flat roofs will be covered by typically one of three types of product. Each of theses products can have several variations and colors associated with them. There are an additional three variations of membranes used but these are not as common and are only listed for reference. Choosing the right system with the initial cost, maintenance, warranty and life expectancy for each system factored in, is where the conundrum begins.

 

The three most common types of Single-Ply flat roof systems:

  • TPO – Thermoplastic Polyolefin (TPO is a blend of polypropylene and ethylene-propylene rubber.)
  • EPDM – Ethylene Propylene Diene Monomer (synthetic rubber)
  • PVC-  Polyvinyl Chloride (PVC is produced of ethylene ,oxygen and hydrochloric acid.)

 

Less common Single-Ply flat roofing systems: 

  • CSPE – Chlorosulfonated Polyethylene
  • KEE – Ketone Ethylene Ester.
  • PIP –Polyisobutylene

 

The Basic Differences

 

TPO

TPO is the most widely used roofing product installed in the U.S market and this is mainly for two reasons. First it can be the least expensive choice and secondly because of TPO’s color, it’s white. The latter reason is becoming less of an advantage for TPO, now that the other systems are now available in white or with white coatings. Even EPDM is available with a white laminated top coating or can be finished or coated with a reflective elastomeric top coat. TPO roofing systems combine the durability of EPDM membranes with the performance of a heat welded roofing system (meaning the seams are “melted” or welded together).

 

Most TPO systems are installed as white, taking advantage of the inherent reflective properties, however, most manufactures can customize the color of membranes including popular options such as gray or tan. A quality TPO roofing system starts with a membrane constructed and produced by a reputable manufacturer. Jottan-Jorel uses trusted brands such as Carlisle, Firestone, JM, Versico and GAF when installing TPO roofing systems.

 

TPO is supplied in relatively small rolls. The rolls average about 8 feet wide by 50 or 100 feet long. This can translate into a tremendous amount of seams created during the installation process of a large flat roof surface. Seams are inherently the weakest part of any roofing system. The more seams that have to be field-welded or glued allows for more human error. TPO should always be installed by a quality contractor who takes the time and employs skilled craftsmen.

 

The primary thickness of a TPO membrane is 45-mils with 60-mils now becoming the norm. TPO is also available up to a 80-mil membrane. Furthermore, making a roofing membrane thicker also makes it heavier, which makes it more expensive and costlier to ship. In addition to the added cost the thicker membrane will add more weight to the structure and is harder to properly seam in the field.

 

EPDM

EPDM is a synthetic rubber, and its most obvious characteristic is that it is black. The market has been moving away from black membranes in favor of white or more reflective membranes. The Federal Government and public opinion on global warming has affected the market when it comes to color choices. EPDM is available in white but this is a composite layer built almost entirely with black EPDM and a white laminate. This composite membrane is more costly than the standard black and if it’s the color white that you are looking for, then TPO or PVC should be the choice.

 

A properly seamed and installed black EPDM roof does especially well at handling rain, snow, UV, roof traffic and ozone. One advantage of an EPDM roof over TPO is that the average sheet size is larger. Whereas the standard TPO system comes in rolls up to 12 feet wide, and EPDM sheet can be ordered in a 50 foot by 50 foot membrane. The larger the membrane the fewer the seams needed. The average thickness for an EPDM membrane is about 45-60 mils and can be ordered in thicknesses up to 90 mils.

 

Because of EPDM’s black color and the amount of energy that is absorbed, these higher temperatures can cause the membrane, especially at the seams, to begin to shrink and pull apart. This is one reason why EPDM is often coated with a reflective elastomeric top coat.

 

As with all roofing systems, the seams are the weakest link. With an EPDM roof, the membrane can last a long time, but the seams, even when properly installed can dry out, shrink, and cause problems. Maintenance is a critical factor in the decision to install an EPDM membrane. Proper maintenance of the EPDM seams, usually with a white roof coating to keep them cooler, will help prevent shrinkage and extend the seams life to that of the membrane. In addition to the additional maintenance an EPDM roof will need, be aware that an EPDM membrane is installed differently than TPO or PVC. Unlike TPO and PVC roofs that are often mechanically attached, an EPDM roof can either be fully-adhered or mechanically fastened with a reinforced membrane. If the EPDM membranes are glued or adhered to what’s underneath, then the seams are either glued with the rest of the roof or they are taped. If the EPDM membrane is mechanically fastened, then the system incorporates a strip of reinforced EPDM along with two strips of self-adhesive splice tape, laminated along each edge over the length of the strip.

 

PVC

Most PVC membranes are mechanically-attached, though fully-adhered or even ballasted PVC roofing systems are still occasionally found. Like TPO, PVC membranes are heat-welded at the seams. This creates a monolithic structure that is very durable and able to withstand the constant expansion and contraction of the building structure throughout the day. A properly heat-welded seam is preferred over a glued or taped seam.

 

Though PVC membranes have excellent puncture and heat resistance qualities, it is absolutely incompatible with asphalt-based products. So if a PVC roof is to be installed in such a way as to come in contact with any asphaltic product, separator sheets must be installed to keep the PVC from directly contacting the asphalt.

 

PVC is relatively light and can be acquired in rolls of 36 and 90 mils. However, the standard PVC roofing membrane is between 40 and 60 mils. Though the primary color of a PVC roofing membrane is white, it as well can include popular options such as gray, tan or black. It also has excellent resistance to bacterial growth, animal fats, as well as plant roof penetrations.

Flat Roof Choices

 “What roofing system should I choose?”

To properly answer that question, a qualified roofing contractor will have to be consulted. They will not be able to properly answer that question until an evaluation of existing conditions has been done. That’s why it is so important to choose a contractor that has your best interests in mind when discussion your roofing options.

 

Some questions to keep in mind:

  • Will there be fees to transfer the warranty if the building owner changes?
  • What, if any fees for inspection to keep the warranty in force?
  • Are there specific exclusions or specific inclusions for ponding water?
  • Is it a prorated warranty or does it cover 100% for the full term?
  • Is the warranty long and complex or short and specific?

 

There are many factors that must be considered when choosing the right system for your roof. It is critical that the installer match the right membrane technology with the right roof system. Jottan-Jorel offers a variety of commercial roofing solutions, including TPO, PVC and EPDM Membranes, for your new or existing structures. Jottan-Jorel specializes in preventive maintenance, emergency repair and service along with new and reroofing services.

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