On 1/25/2016 3:25 PM, Don Y wrote:
On 1/25/2016 12:59 PM, Frank wrote:
On 1/24/2016 2:19 PM, wrote:
My brother has 20" of snow on a 5/12 roof in Maryland, and rain has been
forecasted for Tuesday.

Is the greatest danger from snow weight or from ice damming?

What would be the best strategy for the next 24 hours?

Thank you very much in advance.

Jutta Gibb


Off hand, I'm thinking that this is about 350 lb of snow.

What???! Did you slip a decimal, or so??

I've been wondering about my deck in the same situation and it would
amount to
several people which the deck could easily handle.
If he can safely walk around on the roof, it should be safe but if not he
should probably push off what he can.

You might check my calculations which I just did in my head
considering an inch
of water is equivalent to a foot of snow.

An inch of rain is about 10 inches of snow. So, he's got about 2 inches of
water sitting on his roof -- or, 1/6 cubic foot per square foot.

A cubic foot of water is "about" 8 gallons. A gallon is "about" 8 pounds
(pint ~= pound). So, cubic foot is "about" 64 pounds. He's got 1/6
of that -- about 10 pounds per square foot.

But, that's with *0* pitch.

Given that he's got a 5/12 slope (5" rise over 12" run), that's ~22
degrees.
So, there's only ~9 pounds of DOWNWARD force on the roof (the rest is
converted to a LATERAL force pushing outward against the supporting wall).

Thanks. Did not realize that 5/12 meant slope and that it was not a
flat roof. Have read various densities for snow and his could be
heavier. Our snow was fortunately light and easy for my snow thrower.
My calc. would be ~6 lb/ft2 so we are not far off. Sometimes my head
does slip a decimal or more