snow load on roofs - Fiberglass RV
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Old 02-10-2014, 05:17 PM   #1
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snow load on roofs

I stopped in on a local trailer in Winnipeg (River Heights) area and reminded the owner to clear the snow load off his vintage boler,he {Mike} said that it was his wifes and that he had not thought of the snow load and thanked me.

Just trying to save a owner form some springtime grief, his trailer had full sunlight from the south and as the snow melts the load gets heavier.
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Old 02-10-2014, 06:05 PM   #2
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AND, all that snow on top may very well exceed the rating of the axle. Nice of you to stop and remind the owner!
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Old 02-10-2014, 06:14 PM   #3
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My brother doing just that on my mom's Bigfoot.

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Old 02-10-2014, 10:32 PM   #4
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Here in mid-Michigan, I've done 3 times now what you show your brother doing - just about that amount each time! Should've gone to souther AZ this winter.
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Old 02-11-2014, 05:40 AM   #5
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Here in Western NY, I've been on the ladder like Craig's brother oh about 2 times per week since January. My neighbors probably think I'm a kook...can't recall this much snow since I was a kid! I guess I wasn't sure if the roof prep for the A/C would be enough support, so it's better to be safe than sorry! Do owners of stick trailers and rigs worry about this sort of thing? I can't ever recall seeing anybody with a stickie doing this in dead winter.

Such dedicated souls we are, FG RV owners!
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Old 02-11-2014, 08:42 AM   #6
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sorry, double post.
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Old 02-11-2014, 08:44 AM   #7
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I bought one of these this year for clearing snow from the edge of the roofline on my house, as we have had problems with leaks due to ice dams in the past. The handle is an extension handle and can reach up to about 15-16 ft. It also worked great to clear the snow from my Escape's roof. If you have access to the four sides of your trailer, you would not even have to use a ladder.
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Old 02-11-2014, 09:40 AM   #8
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Quote:
Originally Posted by Craig Broughton View Post
, his trailer had full sunlight from the south and as the snow melts the load gets heavier.

Huh? The density goes up, but the total load should stay the same or less, right? Or am I missing something?
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Old 02-11-2014, 11:19 AM   #9
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Nate - The essential measurement that is required for calculating loads is the water equivalent . How much moisture the snow is holding will change the total load drastically. For example i work at ski races and I can tell you that a shovel full of snow in coastal Whistler BC weighs far more than the same shovel full of snow in the Rocky mountains .... reason is the Whistler snow normally contains far more moisture due to warmer temps. In the Rocky mountains it is normally colder resulting in far less water content to volume.
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Old 02-11-2014, 11:28 AM   #10
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I think that what Nate was pointing out is that once the snow is on the roof of the trailer, the total weight of the snow on the trailer roof does not increase just because the snow is becoming denser as it melts.
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Old 02-11-2014, 12:39 PM   #11
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Quote:
Originally Posted by Ice-breaker View Post
I think that what Nate was pointing out is that once the snow is on the roof of the trailer, the total weight of the snow on the trailer roof does not increase just because the snow is becoming denser as it melts.
Snow usually does become much heavier as it melts. As it melts the moisture content can/will increase thus making it much heavier even though it may look like less volume. It the reason you will see people who live in snow country leave 3 feet of more snow on the roof of their homes or cottages for weeks without worrying about it but once it starts to warm up and melt you will see people up shovelling off the roof as fast as they can.

The water content of snow may range from 3% if very dry snow to 33% if wet, heavy snow, to nearly 100% for ice. An inch of water weighs 5.2 lbs. per square foot. As dry snow melts it becomes wet snow.

There is a good explanation of it located here.
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Old 02-11-2014, 01:51 PM   #12
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Hhmm,reminds of a childhood question, what weighs more a ton of gold or a ton of feathers??
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Old 02-11-2014, 02:00 PM   #13
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Originally Posted by cpaharley2008 View Post
Hhmm,reminds of a childhood question, what weighs more a ton of gold or a ton of feathers??
we as adults hopefully all know a ton is a ton whether it be gold, feathers or snow..... what some of us have difficulties with is the concept that 3" of dry fluffy snow may not weigh as much as 1" of denser melting snow.
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Old 02-11-2014, 02:59 PM   #14
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But where does the additional weight come from? Is the snow absorbing moisture from the air?
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Old 02-11-2014, 03:38 PM   #15
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Wikipedia - Snow - (scroll down to Density) gives a far better explanation than I can give you for it.

Per Wiki new snow commonly has a density of around 8% of water. After settling on the ground it goes to approx. 30% water - by late spring it can be as much as 50% water - mostly caused by melting and refreezing.
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Old 02-11-2014, 03:40 PM   #16
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Originally Posted by David Tilston View Post
But where does the additional weight come from? Is the snow absorbing moisture from the air?
Only where the laws of physics don't apply.

The only way for snow to get "heavier" as it melts is for more snow or rain to fall on it, thus adding more water.

There may be an added danger to roofs as snow melts if it causes pooling somewhere on the roof, though.
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Old 02-12-2014, 09:41 AM   #17
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Carol, the snow gets more dense, yes. So a cubic foot of snow will weigh more than it did. But if you have a foot of snow fall on a roof, weigh it, and then weigh it 3 weeks later when it's melted/refrozen to 2-3 inches, it will not WEIGH more. There is no increase in MASS, just in density.
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Old 02-12-2014, 09:44 AM   #18
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Quote:
Originally Posted by Nate R View Post
Carol, the snow gets more dense, yes. So a cubic foot of snow will weigh more than it did. But if you have a foot of snow fall on a roof, weigh it, and then weigh it 3 weeks later when it's melted/refrozen to 2-3 inches, it will not WEIGH more. There is no increase in MASS, just in density.
Did you factor in the coefficient of vapour loss due to the applied solar energy upon the snow mass?
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Old 02-12-2014, 10:49 AM   #19
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Quote:
Originally Posted by Nate R View Post
Carol, the snow gets more dense, yes. So a cubic foot of snow will weigh more than it did. But if you have a foot of snow fall on a roof, weigh it, and then weigh it 3 weeks later when it's melted/refrozen to 2-3 inches, it will not WEIGH more. There is no increase in MASS, just in density.
Your correct when the snow has melted down 9" as you suggest above but my comment was in response to your general comment below that although snow does in crease in density its "total load" doesn't increase, which isn't correct.

Quote:
Originally Posted by Nate R View Post
Huh? The density goes up, but the total load should stay the same or less, right? Or am I missing something?
Bottom line one can not look at their trailer and say I know its good for at least 1' of snow. no 1' of snow is created equal or weighs the same. To many variables.

In areas of frequent snow its not common to go 3 weeks without any new snow falling on another layer of old higher density snow - which can result in that 1' of snow on the roof weighing far more than the first seasonal 1' of snow fall. Also as I mentioned depending on the water content of that original 1' of snow there can be a great weight difference to what a cubic foot of it weighs to start with.

Bottom line is its good practice to remove snow from the roofs of fiberglass trailers and boats as they are just not built to withstand the roof loads created by snow
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Old 02-12-2014, 12:18 PM   #20
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Carol, no doubt that the foot of snow on a camper at the end of a season could weigh more than the foot of snow at the beginning of the season due to the bottom several inches having been partially melted and then new snow fallen on top of. BUT, my original response was in reference to Craig's statement:

Quote:
Originally Posted by Craig Broughton View Post
and as the snow melts the load gets heavier.
And this statement is NOT correct.

And yes, you're right, a foot of snow is NOT a foot of snow. I have no issue there. Just the way that Craig's statement is written looks to me as to say that snow GAINS mass as it melts.
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