Vertex Roofing wants our blog readers in the Northern Virginia area to know that we are here for you if your roof was affected by one of the many tornadoes brought by Hurricane Florence. In this story from ABC Action News, here is information about how Florence has affected Northern Virginia. “Before Florence sputters out for good, it also struck Virginia with a litany of tornadoes. An estimated 15 to 20 tornadoes touched down in at least six Virginia counties Monday, the state’s Department of Emergency Management Joint Information Center said.”
Even if your home was not directly hit by a Hurricane Florence tornado, the fact is that the high winds from tornadoes can affect your roof even if they are miles away from your location. Roofs are designed to resist high winds, but no roof is likely to withstand the most extreme wind event, a tornado. In between breezes and twisters is a whole range of wind speeds that incrementally damage the roof system.
As wind moves over a roof, its effect is not uniform. Certain regions will be subject to higher pressures, such as along the perimeter. “What you’ll find is that at the center portion of the roof you have the lower stresses,” says Frank Laux, principal engineer and co-chair of CTLGroup’s building and facilities practice group. “But at the corners and at the edges of the roof, typically by the very nature of the wind blowing across the roof, it exerts a higher pressure.”
“Depending on the way the wind blows, the shape of the roof and the location on the roof, there will be negative pressure — suction — or positive pressure — pushing, like when the wind slaps your face as you round a corner,” says James Kirby, AIA, associate executive director of technical communications, National Roofing Contractors Association (NRCA). “But most wind damage that occurs on roofs start on the edge of the roof systems,” he says.
“Wind blowing over a roof isn’t a problem until it starts to move materials,” says Kirby. “Materials” may include the membrane itself or the shingles. Anywhere material is even a little bit loose, the suction of the wind is going to raise it up and then the wind can get below it and push it up. Once the underside of the roofing is exposed, rain can get in, but it also gives the wind more to grab on to.
“What you see is a peeling effect,” says Kirby. For example, the edge of the roofing can start to lift up and in the subsequent wind, events get pushed up and over a little more each time until a whole corner of the insulation is exposed. The damage starts small and grows through repeated wind cycles, usually over time. “To avoid this type of wind damage, make sure edge metal that makes the transition from the flat roof to a vertical wall is sufficiently strong for the location, height and expected wind speeds,” Kirby says. “Ballasted roofs can be scrubbed by the wind at the perimeter, moving the ballast,” says Laux. It’s important to check that the ballast has remained in an even layer across the span of the roof and if not to spread it back out.
“The other materials a significant wind event moves about — shards of glass, tree branches and so on — are perhaps the more damaging issue to consider,” says Jim Hoff, research director for the Center for Environmental Innovation in Roofing.
“When people think about wind events they think, ‘oh well, it could tear the roof of my building or my roof could come loose,‘” he says. “But the biggest effect of wind events that I’ve seen is the potential for wind-blown debris to damage the roof.” That means when inspecting the roof after a wind event, it’s not enough to check that areas are tight and that attachments are still good. “Investigating what might have blown onto or across the roof is also necessary,” he says.
Even in hurricane areas, Hoff says he saw very few roofs actually blow off. The roofs were still attached very solidly to the building but were almost shredded with cuts and punctures from flying debris. He’s seen roofs where the rooftop air conditioning units rolled across the roof “like leaves blowing in the wind. The roof was still there, but it was so terribly damaged.” Wind-blown debris also tends to accumulate and clog drains and downspouts. “That could cause problems in the future, and you might not realize that it had been caused by the earlier wind event, “says Hoff.
As you can very well see from the information provided above by the experts in roofs and wind damage tornadoes cause, once things settle down you really need a proper roof inspection done by an expert. There are so many different ways the wind caused by tornadoes resulting from Hurricane Florence could have affected your roof, only a true roofing expert will be able to find any damage. Vertex Roofing offers FREE roof inspections in Northern Virginia. Give us a call right now and schedule your free roof inspection.
Manassas: (703) 595-2224
Glen Allen: (804) 298-7090