Will your roof collapse under the weight of snow? Let’s do the math

We have reached the point in our winter when we have to make an important calculation: is the risk of my roof collapsing under the weight of the snow greater than the risk of me being permanently disabled by falling off it?

Get back inside because the answer is “no.”

So says Reuben Saltzman at Structure Tech, who writes the Home Inspector column for the Star Tribune. If you’re not following him on Facebook, though, you’re not a real Minnesota homeowner.

“There’s nothing to worry about,” he writes on his company’s blog Tuesday.

And you can thank those pesky state regulations that people so love to hate.

Somebody has actually considered this in the state’s administrative rules, which say:

The ground snow load, Pg, to be used in determining the design snow loads for buildings and other structures shall be 60 pounds per square foot in the following counties: Aitkin, Becker, Beltrami, Carlton, Cass, Clearwater, Cook, Crow Wing, Hubbard, Itasca, Kanabec, Kittson, Koochiching, Lake, Lake of the Woods, Mahnomen, Marshall, Mille Lacs, Morrison, Norman, Otter Tail, Pennington, Pine, Polk, Red Lake, Roseau, St. Louis, Todd, and Wadena.

The ground snow load, Pg, to be used in determining the design snow loads for buildings and other structures shall be 50 pounds per square foot in all other counties.

So pick your poison (location) and do the math:

For the Twin Cities metro area, the roof snow load equals 35 pounds per square foot, or .7 x 50. So how much snow does this equal? It depends. As everyone knows, cold fluffy snow is very light, while wet snow can be extremely heavy.

How much does our snow presently weigh? He took a five-gallon “Homer Bucket,” which is about two-thirds of a square foot, and weighed it — 9.5 pounds. So a square foot weighs about 15 pounds per square foot, he figures.

We’re not even halfway to the point where your roof will fall in, he notes, adding that the 35 pound threshold is a minimum weight that must be supported.

If you have ice dams, getting rid of some of the snow isn’t a bad idea, he says. But don’t climb on the roof to do it.

If you don’t have ice dams, find some other way to fight your cabin fever.