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") 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 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. 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 roof systems. The seams of
all systems are then sealed using either an adhesive or a splice tape. Splice tapes have
tested with a higher tear-strength.
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