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