Single Ply Systems
Single Ply Systems: PVC Membranes, KEE Membranes, TPO Membranes, and EPDM Membranes.
Thermoplastic PVC membranes
The development of Thermoplastic PVC Roofing membranes began in the late 50s and early 60s in Europe, other name of the product include; Thermoplastic Vinyl Membranes (TVMs). Considered one of the most versatile, sustainable, and durable membranes in the European and North America markets. The history of the product provides some rocking times but the membranes that were reinforced are still performing in excess of 47 years in Europe and 30 to 35 plus years in the North American market.
In the 60s, two main PVC membrane manufacturers introduced products to Europe, Sarna Polymer Inc or Sarnafil 1962, a swiss-based company, and Trocal 1966, a German-based company, Sarnafil with a reinforced membrane and Trocal with both reinforced and unreinforced membranes. Both Manufacturers have been acquired since by Sika Corp, but only Sarnafil has roof still performing today from the 60’s.
In the North American market, Trocal has a pretty bad reputation, because of some early generation failures due to the membrane being non-reinforced, which caused shrinkage and shattering. These membranes also had issues with plasticizer migration problems, a plasticizer is a liquid chemical compound that makes the Vinyl membrane flexible, if not present it would be as hard as PVC pipe. The plasticizer migration is what caused the membrane to shrink and become brittle. Trocal membranes are no longer marketed and sold in the North American market and haven’t been since the early 90’s. The PVC membranes that are reinforced, such as Sika Sarnafil, Carlisle, Johns Manville (Cooley Private Label), Flex, Fibertite (who makes a KEE Membrane, see KEE Section), Durolast, IB Roofs, GAF, and Bondcote have had good performance since the introduction to the North American Market.
KEE is an abbreviation for Ketone Ethylene Ester, a high-molecular-weight polymer with elastomeric properties and favorable melting properties for thermoplastic processing. Although KEE is most commonly used in roofing, it is also used in geomembranes for secondary containment for petrochemical storage and other industrial chemical applications. It is manufactured solely by DuPont™, under the brand name Elavloy®. There is also an ASTM International standard, ASTM D 6754-10, which regulates the standards for roofing membranes that use KEE. This standard is commonly referred to as the “KEE Standard” and requires that a minimum of 50% by weight of the polymer content of the roofing membrane be KEE. Therefore all roofing membranes that contain KEE may not comply with the “KEE Standard” but still provide many of the same benefits. This molecule can replace plasticizers in roofing membranes as a solution for flexibility that will not migrate out of the membrane. When mixed with PVC, KEE provides many desirable characteristics in roofing membranes, including:
* Easy heat welding due to melting properties
* Resistance to chemical attack
* Weather resistance
* Long-term flexibility
* Resistance to microbial growth
* Energy efficiency
TPO: Thermoplastic Olefin or Polyolefin
TPO membranes are single-ply roof membranes constructed from ethylene propylene rubber. They are designed to combine the durability of EPDM rubber with the proven performance of hot-air weldable seams. They have been tested as having excellent resistance to ozone, are algae-resistant, environmentally friendly and safe to install. The material’s manufacturers are so confident in properly welded seams that the material is sometimes advertised as a monolithic (seamless) roof. Seam strengths are reportedly 3 to 4 times those of EPDM’s adhesive and tape seams.
TPO is highly resistant to tears, impacts, and punctures with good flexibility to allow for building movement. TPO’s are available in white, light gray, and tan with thicknesses of either 45 mils (.045″), 60 mils (.060″), or 80 mils (.080”). The width of the membrane depends on the manufacturer, but they usually come in widths four feet to ten feet and are one-hundred feet in length.
TPO membranes are installed fully-adhered, mechanically-attached or ballasted. Fully-adhered means that the roof is “glued” to the substrate using a special adhesive. What actually happens is the glue creates a chemical bond with the membrane. Ballasted simply means the membrane is loose laid over the top of the roof, sealed at all penetrations and around the perimeter, and then a ballast is put on it to hold it in place. Ballast usually consists of smooth, round, river rock 2″ – 3″ in diameter and is applied at a rate of 1,000 to 1,200 pounds per roof square (100 sq. ft.). Sometimes concrete pavers are used in their place. These average 20 pounds per square foot. Mechanically-attached membranes are those that use some type of special screw-type fastener to secure it. The type of fastener will depend on the type of substrate but all fasteners are generally screw-type fasteners.
Properly installed TPO roof systems have service lives ranging from about 10 to 20 years, depending on the type of installation. Full removal of the existing roof, the amount of slope the roof has, weather conditions, as well as several other criteria contribute to the longevity of a roof’s service life. Typically, if you remove an old roof down to the deck before installing a new one, then the new roof will last longer. Also, the steeper the slope and the less severe the weather conditions, the longer a roof will last. High winds and hail can do a roof in rather quickly.
But remember, the number one ingredient to a good roof system is proper installation.
EPDM stands for Ethylene Propylene Diene Monomer or Terpolymer, which is a thermoset single ply membrane or commonly called “Rubber Roofs”. Thermoset Single Plies are membranes that are completely cured before the installation of the product. These type of products are manufactured in roll form then either taped together or using an adhesive bond. EPDM membranes have been around since the 1960s and were the industry work horse during the 1980s, 1990s, and early 2000s. During that time most systems were installed loose laid and ballasted. EPDM starting loosing market shares at the turn of the century due to the energy efficient roofs or cool roof craze. This caused some of the EPDM manufacturers to come out with a white EPDM, but was taken off the market due to performance issues. Recently, the white rubber roofs were reintroduced to the market.
EPDM membranes can be made in thickness of 30 mils to 100 mils; standard across the industry is 45 mil and 60 mil thicknesses. EPDM membranes have had good performance out of the product, some of the issues that has happened, is the fact that the product typically constricts and shrinks. This will cause the membrane to pull of the wood nailers and walls on a roof. Additionally, ponding water will affect the adhesives and tapes of the seams.
EPDM: Ethylene Propylene Diene Monomer (or Terpolymer which is simply a product consisting of three distinct monomers). EPDM is classified as a Thermoset material which means it is either fully-cured prior to being installed or that it cures during natural weathering after installation. EPDM roofs are single-ply membranes meaning there is only one ply of roofing material, not multiple plies laminated together.
EPDM has been in use on roofs in the USA since the 1960’s and is one of the most common types of low-slope roofing materials. This is because it is relatively inexpensive, simple to install, and fairly clean to work with when compared to conventional built-up roofs. There aren’t the odors and fumes that accompany built-up roofs which appeals to many property owners and managers.
EPDM is a rubber material whose principal components consist of the compounds ethylene and propylene. A flexible rubber matrix forms when a small amount of diene is added to the mix. EPDM is available reinforced or unreinforced with both commonly used; it’s also available in either a cured (vulcanized) or uncured (non-vulcanized) state. Vulcanized EPDM is the most common with non-vulcanized often used for flashing purposes.
EPDM membrane thickness ranges from thirty mils (0.030″ – which I’ve never seen used for roofing) to one-hundred mils (0.100″) with the most common thicknesses being forty-five mils (0.045″) and sixty mils (0.060″). There are three standard application procedures: (1) fully-adhered; (2) mechanically-fastened; (3) loose-laid. Fully-adhered EPDM uses water-based or solvent-based adhesives to adhere the rubber to the substrate. Mechanically-fastened EPDM is attached by manufacturer-approved mechanical means to the substrate, and loose-laid membranes are secured only at the perimeters and any penetrations, then a ballast of round river rock or concrete pavers is used to hold the materials in place. River rock is usually installed at a rate of 1000 – 1200 pounds per roof square (100 square feet) and the pavers generally weigh approximately 20 pounds per square foot. Structural integrity is important with loose-laid ballasted roof systems. The seams of all systems are sealed using either an adhesive or a splice tape. Splice tapes have tested with a higher tear-strength.
How Long Do They Last?
As with most roofs, EPDM rubber roofs have varying lifespans that depend on numerous criteria. These include environmental conditions such as what type of building (factory or church), how much foot traffic the roof gets, how much water remains on the roof after a rain, and how long it take that water to evaporate. Not to mention geographical location. Roofs in mild climates will outlast roofs in harsher climates. Of course, one of the most important factors in a roof’s life expectancy is quality of workmanship. If the roof is not properly installed, then its lifespan will be shortened.
Properly install EPDM rubber roofs should last between 12 and 25 years. Here’s a brief breakdown base on observations over the past 15 years::
- 45 Mil Ballasted EPDM Rubber properly installed that drains well – 12 years
- 45 Mil Mechanically Attached roof properly installed that drains well – 12 years
- 45 Mil Adhered roof properly installed that drains well – 12+ years
- 60 Mil Ballasted EPDM Rubber properly installed that drains well – 12+ years
- 60 Mil Mechanically Attached roof properly installed that drains well – 15 years
- 60 Mil Adhered roof properly installed that drains well – 15+ years
- 80+ Mil Mechanically Attached roof properly installed that drains well – 20+ years
- 80+ Mil Adhered roof properly installed that drains well – 20+ years
- 80+ Mil Fleeceback Adhered roof properly installed that drains well – 25+ years