EPDM rubber (ethylene propylene diene monomer (M-class) rubber), a type of synthetic rubber, is an elastomer characterized by a wide range of applications. The M refers to its classification in ASTM standard D-1418; the M class includes rubbers having a saturated chain of the polymethylene type. Dienes currently used in the manufacture of EPDM rubbers are dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and vinyl norbornene (VNB). EPDM rubber is closely related to ethylene propylene rubber (ethylene propylene rubber is a copolymer of ethylene and propylene, whereas EPDM rubber is a terpolymer of ethylene, propylene, and a diene-component.

EPDM is an extremely durable synthetic rubber roofing membrane  (ethylene propylene diene terpolymer) widely used in low-slope buildings in the United States and worldwide. Its two primary ingredients, ethylene and propylene, are derived from oil and natural gas. EPDM is available in both black and white, and is sold a broad variety of widths, ranging from 7.5 feet to fifty feet, and in two thicknesses, 45 and 60 mils. EPDM can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system sealed with liquid adhesives or specially formulated tape. 

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1. WHAT APPLICATIONS ARE SUITABLE FOR EPDM MEMBRANE?

EPDM membrane can be used for low and steep slope roofing, as well as unusually shaped structures (such as domes, barrels and other geometrically shaped roofs) due to its versatility. The membrane can be adhered, mechanically fastened, or loose laid. It can be installed above or below insulation (i.e., an IRMA application), and can also be used in below grade waterproofing applications.

Unlike most asphalt base products that are limited in their installation to a fully adhered application and have restrictions of ponded water, EPDM membrane can be used successfully in exposed or concealed assemblies due to its ability to withstand temperature extremes and resist the absorption of moisture.

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2. HOW IS EPDM MEMBRANE SPLICED TOGETHER?

Two methods of splicing are currently available using either liquid adhesive or splice tape.

When using liquid adhesive, adjoining sheets are cleaned with the manufacturer's recommended splice cleaner prior to applying the splicing adhesive. A sealant is used along the edge of the splice and is applied after allowing solvent in the adhesive to flash off (minimum 2 hours). Some manufactures have also used an additional sealant within the overlapping area that is applied immediately before putting the splice together. The sealant is intended as a secondary protection to guard against moist penetration in the event of workmanship error at intersections with factory seams.

The second method of splicing was developed to speed up the seaming processing while maintaining consistent application across the entire seam. This process introduced the use of an adhesive tape in conjunction with a splice primer. The adjoining membranes are primed then the tape is applied once the primer has dried. No additional sealant is used along the edge of the splice. This method has become more favorable due to application consistency.

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3. WHAT TYPES OF IMPROVEMENTS HAVE BEEN MADE TO EPDM SPLICING TECHNOLOGY?

The introduction of membrane splice tapes as an option to the use of liquid adhesives has resulted in less reliability on contractor workmanship, increased production for the contractor, and enhanced performance for the roofing system and building owner.

Laminated components (flashing components that have a pre-applied adhesive tape) have improved flashing quality (an item that has traditionally been problematic).

Equipment utilized to install EPDM single-ply roofing systems has also evolved as well. Innovations have been made to ease the backbreaking work of roof installations - this helps reduce work force fatigue and enhances the installation and performance of the roofing system.

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4. REGARDING AGED EPDM MEMBRANE, WHAT TYPE OF SURFACE PREPARATION IS NEEDED TO PERFORM ANY NEEDED REPAIRS?

Because EPDM is a thermal set membrane at the time of installation, no additional curing will occur. Repairs can easily be performed with simple tools and accessories without the need of heavy-duty equipment.

For example, a cut or tear can be repaired by cleaning the membrane surface to remove field dirt (brooming in addition to washing with low sudsing soap and rinsing). The area is then primed and a laminated patch is used to seal the cut or tear.

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5. ARE TEMPERATURE LIMITATIONS ASSOCIATED WITH THE INSTALLATION OF EPDM ROOFING SYSTEM?

In accordance with ASTM standard D 746, EPDM membrane has a brittleness temperature of -49 F. While the membrane will remain flexible and pliable in extremely cold temperatures, adhesives, flashings and tapes should be kept at room temperature (hot boxes are usually used on the rooftop to rotate adhesive cans and rolls of flashing). Although roofing contractors may select not to work in sub-freezing temperatures due to safety concerns, many EPDM installations have taken place in temps below 20 F.

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6. WOULD A MANUFACTURER'S WARRANTY BE TERMINATED DUE TO PONDING?

Ponded water on an EPDM roofing system will not void a manufacturer's warranty or be the sole reason to deny issuance of a warranty. During the design phase, however, efforts should be made to incorporate positive drainage into the roofing assembly to avoid excessive ponding. It is beneficial to avoid ponding water due to the expense associated with its removal in the event of repairs and also to reduce moisture infiltration and damage in the event of incidental puncture.

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7. WOULD REPAIRS TO AN EPDM MEMBRANE BE IMPAIRED BY AGING?

No. One of the most unique attributes of EPDM is its ability to be easily repaired as well as its potential for restoration unparalleled in the roofing industry. The characteristics of the membrane are such that, even after years of field service and exposure to the elements, repairs and/or modifications, such as the installation of a new rooftop unit, can be accomplished with ease and with the expectation of long-term performance.

Unlike other roofing systems that degrade or become brittle over time due to UV exposure, EPDM single-ply membrane maintains its integrity and flexibility. This allows for modifications as easy as washing the membrane, preparing the roofing membrane surface, adhesive applications, and the installation of new material.