Versico is one of the largest manufacturers of EPDM single-ply roofing systems.  EPDM has been in use in the USA since the 1960's and is one of the most common types of flat and low-slope roofing materials.

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.