Flat roofs are difficult to install properly, and as a result, many don't last for anything close to the life span they're capable of achieving. In this article, roofing specialist Dyami Plotke describes his process for getting the details right so that a low-slope EPDM roof can last for 20 years or longer of leak-free service. Plotke begins by making sure he's working on a stable substrate, such as high-density. gypsum board. He also lines up an assortment of appropriate sealants—urethane, water-block mastic, and lap caulk—and uses them in the correct locations. Seams between sheets of EPDM should be connected with a special 6-in.-wide seam tape; avoid the urge to use splice cement, which is seldom applied correctly and often fails prematurely. Pieces of edge metal, such as gravel stop and drip edge, are sealed in place. Also, sidewalls are a critical joint that requires counterflashing. If the roof has any pipe penetrations, they can be managed with boots, preformed pipe seals made from molded EPDM.