The Snow On Your Roof Weighs 7 To 20 Pounds Per Cubic Foot

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2015 has brought ‘tons’ of record snow onto the roofs of buildings all across New England. The weight load of the accumulated snow on a roof is astounding, and dangerous.

Today I had the pleasure (sarcasm) of shoveling most of the snow off the roof of my 5th-wheel trailer. I should have shoveled it sooner, but it being parked not so close to the house I wasn’t paying it much attention – until yesterday’s snowfall – when I suddenly realized the predicament and hoped that this wasn’t the ‘straw’ that’s going to ‘break its back’ (or roof!).

I just calculated how many pounds of snow was probably sitting there…


 
With the trailer slides in, the roof dimensions are 36 feet by 8 feet (288 square feet). I estimated that about 2.5 feet of snow was on the roof. That amounts to 720 cubic feet of snow. Light fluffy snow weighs about 7 pounds per cubic foot, while heavy wet snow can weigh up to 20 pounds. I’ll estimate 7 pounds per square foot in my case. So the total weight up there was about 5000 pounds! or 2.5 tons of snow on the roof! Yikes…

I am very thankful that the roof held up. What may have saved it was the fact that the roof isn’t flat, but bowed – which would have been sending some of that weight load down the side frame (compared to a flat roof).

Roofs have been collapsing all around New England this winter, but if you have a camping trailer – be especially aware of the trailer roof because they are not nearly as strong as the roof on your home! Once the roof collapses, your SOL and your camper will be ruined. Don’t let it happen ;)

And the snow keeps coming…

 
The longer you let the snow accumulate on the roof (storm after storm), the more compact it will get – and the heavier it will get (dense – especially near the bottom). I had to leave the bottom 4 to 6 inches alone as it was a mixture of ice and snow.
layers-of-snow-on-roof

 
‘Yours truly’ shoveling in below-zero wind chill today. Thanks to Mrs.J for capturing the images from the warm cozy kitchen window.

As an aside, whenever I’m away from the house out on the property, I always take a portable GMRS 2-way radio for comms back to the house. A word of caution: if it falls into the snow, especially if you don’t realize you did it, have fun finding it… I had to go back to the house and get another radio and talk into it while walking around and re-tracing my steps. I finally found it as my voice emanated from deep within a particular snow drift ;)

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15 Comments

  1. Holly shito dude, can ya send some of that back to here in New Mexico? it’s dryer than a popcorn **** here, no rain, no snow, Nada Nothing. Even Wolfcreek (look it up) has less than 50% of snow fall. Not a good outlook for the entire western US. Can anyone say Drought? or 30 year drought as in the great depression? Just wait till the floods there this spring
    Keep you powder high and dry my friend
    NRP

    1. Here in the Oregon Cascades we only have 10 – 14% of normal snowpack. Some of the lower ski resorts opened briefly in December, but then had to close again. Just saw a picture of Hoodoo Ski Bowl the other day. No snow – none. It’s rained a decent amount, but no snow. The rivers are gonna be low this summer!

  2. Wow, I have to say that is a bunch of snow. Growing up on the U.P. of Michigan I had friends in high school who made a small business shoveling peoples roofs off. It was just what you did. We averaged 150″ a year up there. Also in regards to roof loads. I am not sure what ASCE7-10 (minimum design loads for buildings) calls out for the northeast but in WI/Upper MI/MN I know the building codes call out a roof live load of 35 psf, that is a lot. If you would like to find out what your ground snow depth is and an approximation of what the density of the snow is check out this NOAA website. I use this all the time for work. A simple calculation will allow you figure out the weight of snow on your roof.

    http://www.nohrsc.noaa.gov/interactive/html/map.html

    1. @Northern Boy, Thanks for the link and the building code (35 psf) in your area.

      That calculates to be the following max snow depth:

      5 Feet of fluffy snow (7 lbs/ cubic ft)
      1.75 Feet of heavy wet snow (20 lbs/ cubic ft)

  3. We are having a snow drought this winter too, and you are getting what we have had the last two years. Shoveling roofs is good exercise as I did it with a broken rib for therapy.

    I live in the land of lakes watershed but the drought we are having now under current conditions will affect us to close off the dams on the Mississippi River to a trickle.

    There will be MEGA droughts in the west this summer according to NASA who predicts that they will last many years and worse than what we had years before. If this prediction comes true, then Ken, your area will be the lucky place to be, snow and all.

  4. Kind of makes me think we need a new pipeline (aqueduct). but where would we get the manpower to construct it. Oh wait, we have jails and prisons overflowing and releasing criminals early that could possibly supply the labor? I can’t help but think of all that flooding the Mississippi does yearly just flowing into the gulf instead of watering crops.

    1. Have been saying this to the wife for years. They need to be harnessing some of the the flood waters to storage for later needs. Dont know about jailbirds, hell all the people who have fallen off the end of the “un-employment” system and are no longer counted by the government could be working for years.

  5. @me: One of the reasons so much of the nation’s food has been produced in California is the artificial / industrial nature of large scale Ag there. The middle of the USA is easily capable of replacing what is lost in California – just will be more expensive.

  6. David, I hope they get it geared up. Very good point about the scale of big AG here. Driving the I-5 corridor and you see signs about the drought being artificial and how many jobs are being endangered by water restrictions. Most of California’s water comes from the snowpack and that is something that can be and has been measured on a yearly basis. A lot could be saved by different irrigation practices and frankly, a lot of the crops are luxury foods. We need corn, wheat, rice, potatoes and such. Not so much need for almonds, cherries, cashews and the like. Lots of people depending on their jobs growing them and I do have to admit though that I’m fond of cashews.

  7. So today (the day after I shoveled the roof of the 5th-wheel) I spent much of the day with a ‘snow rake’ getting as much snow off the roof of the house that I could reach.

    One half the roof I cannot get because it’s too high off the ground to reach. The other half was reachable since I have a deck off the 2nd-floor on that side that runs the length of the house.

    There was about 1.5 feet of snow up there, and I’ve got to tell you, I was very surprised how heavy it was. While every snow storm so far this season has produced light fluffy snow (80″ so far), the snow compacts (heavier) over time (likely from the sun (and gravity) slowly working on it – even though it has been below freezing here for months).

    I would guess that this stuff weighed closer to the 20 pound per cubic foot – maybe it was 15 pounds – especially the snow on the bottom half of the stack.

    I’m just mentioning this for any others who happen across this post while doing a web-search or something. Be aware that the snow on your roof is probably 10 to 20 pounds per cubic foot if it’s been accumulating there over the winter and has not melted off.

    My house isn’t that big (2-story footprint 28×40) but I’m estimating that I removed between 5000 and 10000 pounds off one half… That’s like having my F350 parked up there on one side! At least I’ll sleep better tonight while looking up at the ceiling ;)

    And guess what – it’s snowing again right now!

  8. Meanwhile, here in sunny so-cal, we’re having round 2 of “The Winter That Never Was.” Normally this time of year we will have had several feet of snow. We’ve only had a few inches. I’ll trade Ken some 70 degree days for some decent snow. We’re getting kinda thirsty ’round here.

  9. For you out west – you all can have some of our snow if you’d like… ;)

    3 feet of snow sitting on the ground here this morning… 5 more inches last night and had to fire up the snow-blower again.

    3 feet of snow

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