February’s record snowfall total - with more on tap this weekend - no doubt has many wondering how much more of the fluffy white pestilence they can take.
Some homeowners might be wondering the same thing about their roofs. Can they withstand the weight of winter? Heavy snow caved in the roof of the Metrodome in December, 2010. How much snow on the roof is too much?
“Unfortunately, that’s not an easy question,” said Cottage Grove building official Bob LaBrosse.
Generally, most roofs are designed to carry at least 50 pounds per square foot, he said.
“It would take a lot of snow to damage a roof to actually collapse it. If you had four feet of snow on your roof you probably would have a problem.”
While some wags might say that it looks like we could get there, the primary concern is that layer of ice that collects on the edges of a roof.
Ice dams form from snowmelt caused by heat escaping through a home’s attic. The water trickles down to the roof line and refreezes. More snow melt pools, possibly seeping into shingles, cracks, skylight flashing or roof vents and finally, through the walls and ceiling.
“Anytime that a couple feet of snow that gets on the roof, there’s the risk of an ice dam being created, said Chad Oberle, estimator and project manager for Roof Tech in Stillwater. The snow can also clog roof vents, he said.
“The general rule is, if you have concerns about an ice dam, remove about six feet up from the bottom of the eave and pull that snow off your roof.”
Homes built before the mid-90s are generally more susceptible to ice dams, LaBrosse said. State building codes have since been updated to reduce heat leakage.
“A newer home that has very good attic insulation and ventilation really doesn’t have a problem with the loss of heat form the interior of the building getting up into the attic,” LaBrosse said.
If your home was built in the mid’90s or earlier, some proactive cleaning with an ice rake can’t hurt, LaBrosse said.
Ladders can be risky, however.
“If you have a two foot overhang, try to clear that,” he said. “Leave a layer of snow up there. This way you wouldn’t be damaging your shingles.”
Large icicles on a roofline can be a harbinger of headaches, LaBrosse said.
“When I drive down the street today and I see houses that have large icicles, those are the ones that are going to be problematic in the spring,” he said. “Those roofs are talking to us saying, ‘We’re losing a lot of heat through that roof/attic system.”