Installing a Low-Slope EPDM Roof
Done with care, a flat roof can provide 20 years of leak-free service.
Synopsis: 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.
Although we do a fair amount of residential roofing, my family’s bread-and-butter business is installing low-slope commercial roofing. A properly installed commercial roof can last for 20 or even 30 years. Unfortunately, many residential roofers are poorly trained in low-slope roofing techniques, so their flat roofs may last only half as long. When our company does residential low-slope roofing, we use commercial methods and materials, so our residential flat roofs last a long time with minimal maintenance.
The small sunroom on this 1930s stucco house is typical of what we find when we replace a residential flat roof. This old roof was hot-mopped asphalt, a once-reliable roofing system that is disappearing rapidly because of asphalt’s high price and diminishing quality. Nowadays for this type of roof, we use an…