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LSR is a certified installer of Carlisle, Johns Mannville, and Firestone. The EPDM (ethylene propylene diene terpolymer) rubber roofing membrane has been an appealing choice of the low-slope commercial roofing industry for more than 40 years, with more than 500,000 warranted roof installations on 20 billion-plus square feet. Annually, EPDM accounts for over 1 billion square feet of new roof coverings in the United States, and is the most frequently used roofing material in the marketplace. According to National Roofing Contractors Association (NRCA), EPDM continues to be a top roofing choice of architects, roof consultants and contractors for both new construction and replacement roofing projects holding approximately 25% of the market share.

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EPDM is composed of propylene and ethylene and is technically recognized as a thermoset single-ply membrane. Unlike other single-ply membranes, a thermoset membrane is chemically cross-linked, the official term is “vulcanized”. These materials tend to be much less gummy than thermoplastics. Additives or curatives (sulfur) bring a more rubberized characteristic to the 7.5 to 50 foot wide sheets making them more durable and flexible to handle. Inherently, when you hear roofers describing a rubber roof, they are likely describing an EPDM flat roof.

The ethylene content is around 45% to 75%. The higher the ethylene content the higher the loading possibilities of the polymer, better mixing and extrusion. Peroxide curing these polymers gives a higher crosslink density compared with their amorphous counterpart. The amorphous polymer are also excellent in processing. This is very much influenced by their molecular structure. The dienes, typically comprising from 2.5% up to 12% by weight of the composition, serve as crosslinks when curing with sulphur and resin, with peroxide cures the diene (or third monomer) functions as a co-agent, which provide resistance to unwanted tackiness, creep or flow during end use.

EPDM membrane thickness ranges from thirty mils to one-hundred mils 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 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 does an EPDM roof 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 does the roof get, how much water remains on the roof after a rain, and how long does it take the 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 installed EPDM roofs should last between 12 and 25 years.

Based on our experience with the product, it is typically a little more expensive to install. While we install the product per specification, we have found that for the value there are more efficient systems available affording the same, if not better, longevity and durability.