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Experts say many roofs can handle snow weight

Tue., Dec. 23, 2008, 6:28 p.m.

Despite a record snowfall and more on the way, most homeowners don’t need to worry about clearing their roofs of snow. Not yet, anyway.

Local building codes require new buildings to hold about 30 pounds of snow per square foot, engineers said Tuesday. Roofs up to code should hold snow that equals about five inches if melted. On Tuesday, the National Weather Service reported that the snow on the ground in Spokane is the equivalent of about 1.4 inches of water.

The snow so far has been light and powdery. “It’s not insignificant, but it is not big,” said National Weather Service Meteorologist John Livingston.

Last winter, the most that was on the ground at the airport contained about 2.5 inches of water, Livingston said.

The snowpack is expected to grow this weekend with a storm forecast to bring wetter snow. Officials recommend keeping an eye not so much on the amount of snow, but on the weight.

Building experts note that while newer homes were constructed under more stringent codes, older homes survived other severe winters, like in 1949.

Structural engineer John Cuddy said carports and awnings are probably at the greatest risk.

Otherwise, for most homeowners “shoveling snow less than about three feet deep is probably unwarranted,” said Cuddy, who works for Integrus Architecture. “Homeowners should weigh the risk from the personal injury from a fall against the peace of mind that might be gained from snow removal.”

Still, there has been at least one snow-related collapse. On Tuesday morning, the roof of Inland Empire Drywall in Spokane Valley gave way. No one was in the building, at 5105 E. Railroad Ave., when the snow overwhelmed a 40-by-20-foot portion of the shallow-peaked roof about 6:15 a.m., said Bill Clifford, Spokane Valley Fire Department spokesman.

Terry Danzer, Spokane’s deputy building official, said his department began receiving calls from residents concerned about snow on their roofs after news broke about Inland Empire’s collapse.

Danzer advises folks to consider removing snow from roofs once it hits around 24 inches. If the coming storms dump a lot more, Danzer said he would consider removing snow on his roof.

But he cautioned that doing so can be dangerous and that many roofs can hold much more.

“It’s a very difficult question to answer without knowing all the different variables involved,” Danzer said. “It could hold a lot more, but I don’t know that.”

Engineers said shoveling snow off a home might cause damage to the roof and that, in some cases, the weight of a person pinpointed on a weaker part of the roof could cause a bigger structural problem than not shoveling off the snow.

Ken Pfaff, who owns Criterium-Pfaff Engineers, said owners should look out for ice dams that stop water from draining. He agreed that most folks don’t need worry about clearing their roof until it gets closer to the building-code limit.

“When it gets to be a problem is when it starts to rain,” he said.


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