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MARQUETTE COUNTY- It’s part of winter in the U.P. for some people: clearing off the roof. But is it necessary? Let’s look at the numbers:
If your home was built after 1979, it should be designed for a minimum snow load on the roof of 60 pounds per square foot according to most regional county building codes.
Rod Lizak, a State Farm Insurance agent says, “Most insurances will cover if there’s a complete collapse. The bigger concern often is sagging roofs. Sagging roofs, just from the shear weight, generally is not covered by insurance. Some companies may, but not all companies do.”
Four feet of snow on a roof could weigh more than 70 pounds per square foot. That means a 600 square foot garage roof could have more than 42,000 pounds of snow load. That’s 21 tons.
Gary Niemela, owner of Skandia Truss, told Local 3 News, “You can look at my buildings out here, even from where I’m standing, I can see three to four feet of snow on that building. And it’s a 60 foot clear span. That’s like having a freight train of weight up there.”
So if you have an older home, one with a flat roof, or a pole barn-type building with widely spaced trusses, you may want to clear off some of the snow. But what if you don’t remove the snow and the roof caves in?
“A complete collapse is generally covered. Anything less than that, as a rule, is not covered. Leaks can be, generally what happens is that’s caused by ice dams. Ice dams are caused by lack of insulation and ventilation in most cases and insurance generally covers damage that’s caused, not what causes the damage,” said Lizak.
You can take the chance that your roof will withstand the weight of the snow, but if you choose to remove it yourself, or hire a crew or a friend, be careful that you don’t fall off the roof or damage the shingles.
To calculate the approximate weight of the snowload on a roof, click here.
For another calculator, click here.
The following additional information was provided by Michael T. Drewyor, PE, PS, Michigan Technological UniversityProfessor of Practice, School of Technology; Roland A. Mariucci Professor of Practice, Civil and Environmental Engineering; Faculty Advisor: Associated Schools of Construction (ASC).
- Snow can weigh anywhere from 5 to 18 pounds per cubic foot (pcf) or more.
- Four feet of snow on a roof could weigh over 70 pounds per square foot (PSF).
- A 600 sft garage roof could have over 42,000 pounds of snow load (21 tons).
- It is not uncommon to get drift loads of snow that can approach 200 psf of roof area. (ie, low roof adjacent to high roof, often typical at school buildings).
- New roofs (post 1979) in the Copper Country should all be designed for a minimum snow load on the roof of 60 psf (Houghton Co. Bldg Ordinance) and most are 70 to 75 psf.
- Design “ground snow load” here in the CC is ~ 95 psf .
- The actual roof snow loads are reduced due to exposure, etc.