New snow on still-unmelted old snow is piling up in Central Oregon, weighing down roofs across the region.
With nearly 8 inches falling on Wednesday across Bend, it isn’t a situation a homeowner can ignore.
City building codes across most of Bend require roofs to support a load of 20 pounds per square foot, while codes in snowier communities at higher elevations require even stronger roofs — 45 pounds per square foot in Black Butte Ranch, 55 pounds per square foot in La Pine.
The weight of snow varies significantly. A 2013 FEMA report puts the weight of 12 inches of snow between 3 pounds for light, dry snow, and 21 pounds for wet, heavy snow. A square foot of ice, the same report notes, weighs just under 5 pounds for every inch of depth.
Billy Stayton, with the city of Bend community development department, said there’s a lot of wiggle room in the snow load code standards — after all, people weighing much more than 20 pounds can stand on a roof without caving it in. Still, too much snow can cause a roof to fail, he said — the roof of an industrial building on Bend’s north side collapsed in December, and in late 2014, the roof caved in at Prineville’s Woodgrain Millwork.
“If I saw three feet of snow up on my roof I’d probably be saying its time to go up and get that off,” he said.
Craig Junker, owner of River Roofing, said while it is possible for snow to pile up to the degree it threatens the stability of a house or a building, the primary danger in Central Oregon is ice dams, an accumulation of ice on the roof that can lead to flooding inside.
Junker said he’s seen snowier years over 22 years of running his company, but the ice buildup this winter is the worst he’s seen. His crews have been busy in recent days, shoveling snow off roofs to combat ice dams.
As Junker explains, the formation of an ice dam begins with heat escaping from inside the house melting snow on the roof, causing water to run downhill toward the edge of the roof. But because the overhanging edge is not warmed by the heat from inside the house, the melted water refreezes, creating a layer of ice at the edge.
Over time, that layer of ice builds up, Junker said, forming a dam that keeps melting snow from running off the roof to the ground. Liquid water backs up behind the frozen dam, and given enough time, that water can find its way inside the house.
Clearing the snow from the last 3 to 4 feet up from the edge of a roof will help deter the development of ice dams.
While companies like River Roofing will clear snow from your roof for a fee, some homeowners choose to do it themselves.
Junker said those who opt to clear the snow from their own roofs should be cautious and consider investing in a snow rake in order to avoid climbing on to an icy roof. Available at local lumberyards and elsewhere, snow rakes have a long handle that extends far enough to rake the first few feet of snow off a first-story roof without climbing on to the roof itself.
Though there is little snow in the forecast, the snow now on the ground is unlikely to be going away anytime soon. The National Weather Service forecasts suggest Bend and surrounding communities will remain well below freezing until Sunday, when daytime high temperatures will return to the mid-30s.
— Reporter: 541-383-0387, firstname.lastname@example.org