Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, March 17, 1993 TAG: 9303170106
SECTION: VIRGINIA PAGE: A1 EDITION: METRO NOTE: ABOVE
SOURCE: LAURA WILLIAMSON STAFF WRITER
DATELINE: LENGTH: Medium
ROOFS ROOFTOP SNOWDRIFTS RAISE RISK
When a ceiling tile dropped in the offices of Dominion Bankshares Mortgage Corp. and employees heard cracking noises coming from the roof Tuesday, they didn't wait around to see what would happen next.They called the Roanoke Fire Department - from outside the Thirlane Road Northwest building.
As it turned out, the noise they mistook for a collapsing roof was actually the noise of workers a roof collapse. The cracking came from the sound of shovels hitting the roof, clearing it of the weight of the weekend's 16-inch snowfall.
"They were doing exactly what they should have been doing," said Sam Lionberger, president of Lionberger Construction Co. in Roanoke County.
Those who failed to clear the drifting snow from their roofs, or couldn't get to it in time, suffered the consequences. At least nine roofs buckled or collapsed around Western Virginia as a result of the blizzard of '93.
Was it faulty design? Poor construction? Inadequate building standards?
Not likely, said Roanoke Building Commissioner Ronald H. Miller.
State code requires buildings to hold 20 pounds per square foot of snow - more than the 16 inches that fell. But fierce winds blew snow into drifts several feet deep on many roofs, placing them under excessive pressure.
"We're lucky we didn't get more damage than we did," Miller said.
Buildings with sloped roofs, such as most homes, were protected from collapse because snow slid off, he said. While that may create a hazard for people walking around the yard or in and out their doors, it doesn't create a danger for people inside the home.
Especially vulnerable were roofs that were built with more than one level, or low buildings built next to higher ones, Lionberger said.
In cases like that, the higher building or level stops snow from blowing off the roof and creates a lopsided pressure on the lower roof.
That's what happened to the roof at the Stanley Furniture Outlet at Town Square in Roanoke, which buckled under the weight of snow drifting up against Sam's Wholesale Club.
"This was just a fluky thing," said J.M. Turner Jr. of J.M. Turner & Co., which built Stanley Furniture. "The insurance company calls those things acts of God."
The building code takes drifting into account, using a complicated formula based on the height of the "steps," or different levels of roof, Miller said. But it's hard to estimate how much snow will weigh, because it varies depending upon the amount of moisture in it and whether or not it freezes.
At 56 pounds per cubic foot, ice weighs much more than snow, said Dan Zahn, Lionberger's executive vice president. Freshly fallen, dry snow weighs 8 pounds per cubic foot. Water, just before it freezes, weighs 62.4 pounds per cubic foot.
"The worst possible condition for a roof is if you get snow on it and it melts and freezes," he said.
Or if one storm follows another, as was expected Tuesday night. The National Weather Service reported a 60 percent chance of snow, sleet or freezing rain for Roanoke.
"That's going to really put a heck of a load on the roof," Zahn said.
So should people get up there and shovel it off?
"I would," Miller said.