Your Flat Roof Vs. El Niño

Sometimes we take that all-important roof over our head for granted—and forget about it. But this winter that roof will be unforgettable—day after day, some experts predict—as El Niño thrashes us from above. One question: Are you—and your roof—ready?

“People think of their roofs just like you and I think of our plumbing: It doesn’t need anything until it’s leaking,” observes Randy Feriante, owner of Dura-Foam Roofing and Solar Center, a foam roofing installer in Menlo Park. “This is a good year to talk about something like this.”

“A strong El Niño is in place and should exert a strong influence over our weather this winter,” says Mike Halpert, deputy director of the National Oceanic and Atmospheric Administration’s Climate Prediction Center. “While temperature and precipitation impacts associated with El Niño are favored, El Niño is not the only player. Cold-air outbreaks and snow storms will likely occur at times this winter.”

So this winter is expected to be a wet one all across the southern third of the U.S., including Southern and Central California. Significant storms and heavy rains are expected in Northern California too.

Is your roof ready to withstand what’s coming, and how can you tell? Part of the challenge for many modernist homeowners stems from their flat roofs, which can be prone to ponding because of inadequate drainage.

“If you build a house nowadays, it has to have positive slope,” notes John Rossi, longtime general manager of Cal-Pac Roofing San Mateo.

Cal-Pac installs the Duro-Last single-ply system, custom-assembled sheets of polyvinyl thermal membrane. It is one of three main systems used on Eichlers and other modern-style roofs. The other two are a flexible asphalt coating known as modified bitumen, and spray-on polyurethane foam (topped by elastomeric coating), which is what Feriante and Dura-Foam use.

Not all homeowners know the importance of cleaning rain gutters in fall to prepare for winter rains. But it’s an advisable practice—especially when you consider the makeup of most MCM roofs. Some are entirely flat, which can be problematic, while others have built-in slopes.

“The ones that have gentle slope have rain gutters and eaves to let the rain off. You never ever have ponding issues with those,” says Rossi. Alternatively, he says, “A lot of flat roofing does not have rain gutters.”