OTTUMWA — That snow may look light and fluffy, but a few hundred square feet of it sitting on your roof can weigh a ton — or more.
"On average, 6 inches of snow will add 10,000 pounds to your roof load, and this year we are seeing 12 inches to 16 inches," said Anthony Christner, president of Christner Contracting in Ottumwa.
Add some sleet or rain that can soak that foot of snow on a roof, and it's easy to pass the 10-ton mark.
"Newer homes that have engineered trusses instead of traditional rafters ... are designed to handle much of these loads," Christner said. "But in town, we have a lot of older homes built from rafters before there [were] any codes or regulations to follow. Even without the added snow loads, we see a lot of sagging."
This winter, that hasn't been the worst problem.
By the direction they are installed, roofing shingles are meant to shed water, explained Mike O'Hara at O'Hara Hardware. So water coming from above is not typically a problem because rain runs down over the shingles and off the roof. But water coming from below is a different matter.
O'Hara said the problem is when the edge of the roof is blocked; that's when you have the equivalent of a dam around your roof. Water can't run off the roof, so it gets backed up. That forces the water under your shingles, and that water drips into your home or business.
Christner concurred and explained how that happens:
"The number one call we are getting this season is ice damming, and it is up about 50 percent from last year's calls. Ice damming is caused from the heat of the sun and the loss of the heat through the attic melting the snow on our roofs, and in the evening when the sun goes down and temps drop back down the melted snow freezes in gutters and roof edges ... when the snow freezes it expands around and under any shingle that it comes in contact with and forces its way between the sealant on the shingles and allows moisture to penetrate."
Solving the problem takes some effort, but homeowners say it's worth it: Get the snow off the roof, so any melted snow can flow right off.
"They do make a roof rake," said O'Hara, "and we are sold out. But our warehouse did just get some in, and we'll have them [here] Friday."
A roof rake doesn't really look like a rake.
"It has a 21-foot connector handle, but it's real light," O'Hara said. "The [head] looks like a garden hoe, but it's 24 inches wide."
That, said Christner, can save you thousands of dollars in damage. There are more permanent solutions as well, he said.
"It is impossible to stop 100 percent of this effect on roofs but items that can significantly help are have a professional examine the insulation thickness in the attic (at min. you need 12 inches, he said) and pay close attention to where the attic truss or rafter meets the exterior walls," Christner said. "People overlook this area, but [that's] where a lot of heat from your home escapes and creates a perfect spot for ice damming to start forming."
There are other products, though they don't work unless put on correctly. One is a rubberized self-adhearing membrane. A good time to add that is when you're getting your roof redone, though there are ways to do it by removing some existing shingles.
For any roof, Christner's commercial roofing superintendent, Dan VanDevender advises his clients to get an annual checkup. Yet he also said snow and ice damages the flat roofs on many businesses in a different way from the sloped roofs on houses.
"The shear weight alone can cause splitting of the membrane, lap seams to open up, wall flashing and termination to pull away from the walls," he said. "When this happens water can enter the building as melting occurs."
— News reporter Mark Newman is on Twitter @couriermark