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General => General Forum => Topic started by: Bishopknight on March 04, 2008, 09:48:47 AM

Title: How to calculate snowload?
Post by: Bishopknight on March 04, 2008, 09:48:47 AM
Hey everyone  c*

I am trying to figure out how to calculate snowload from annual snowfall in inches. Can anyone show me how?

Taking Harmony, Maine as an example ( with data collected from the National Weather Service ) is there a way to calculate what the PSF would be?

QuoteMonthly Totals/Averages
Snowfall (inches)
Years: 1978-2001

             Jul   Aug   Sep   Oct   Nov   Dec   Jan   Feb   Mar   Apr   May   Jun  Season
Avg      0.0   0.0    0.0    0.4   4.0    13.1  17.4  13.6  12.2   3.2   0.0   0.0    63.9
Title: Re: How to calculate snowload?
Post by: glenn kangiser on March 04, 2008, 10:48:50 AM
It's done for you by the local building officials - usually it's based on a certain elevation in the area you live in and can vary by local conditions.

Here is 30 lbs, but we haven't had over a foot of snow in years.  Wet snow weighs a lot more than dry also - so you just have to ask how much snow the government will allow to fall. :)
Title: Re: How to calculate snowload?
Post by: CREATIVE1 on March 04, 2008, 11:07:58 AM
And sometimes the snow load you have to build for is a little ridiculous, but if you want to build, you've got to satisfy those code people.  Since I'm at 1,200 feet above sea level in Washington, I have to build to 55 pound snow load (above 1,000 feet).  I have been talking to the locals, and they think I'll get snow where I am maybe twice a year.  Plus most of my roof is 12/12 pitch.  But it turns my ridge beams into unwieldy monsters.
Title: Re: How to calculate snowload?
Post by: Willy on March 04, 2008, 11:55:24 AM
All depends on where your located. I have to have a min 70 lb rating on my new cabin I am building and if I remember right it was 125 lb on my home I live in now. Both places are above the 2700 ft level. Mark
Title: Re: How to calculate snowload?
Post by: MountainDon on March 04, 2008, 06:07:38 PM
I'd say when it come to planning a new structure there are two things that are mostly governed by local conditions.

Foundation depths.
Snow loads

Everything in between is more or less the same across the country.

My 0.02
Title: Re: How to calculate snowload?
Post by: davidj on March 05, 2008, 04:21:40 AM
At higher altitudes the snow load can get very local too - even knowing what the house down the road at the same elevation is built to doesn't necessarily mean that your house will be the same.  Our local town of Johnsville is about 3 blocks by 5 blocks but has a range of snow loads.

At 5000ft in the Northern Sierras they tried to persuade us to build to 150psf, but our area was not fully surveyed and legally it was 85psf.  We went for 120psf in the end, which means a 6x18 beam to support a 20' x 20' area of roof.  There is 4' of very wet snow on the ground right now, so I guess there's some justification.

Thinking about it, with a 6x18 I'm gonna be getting into the chainsaw-and-bulldozer end of framing.  I guess I'd better start rereading more of Glenn's old posts...
Title: Re: How to calculate snowload?
Post by: glenn kangiser on March 05, 2008, 12:00:49 PM
Don't forget the sledge hammer.
Title: Re: How to calculate snowload?
Post by: CREATIVE1 on March 05, 2008, 12:07:55 PM
Quote from: davidj on March 05, 2008, 04:21:40 AM
At higher altitudes the snow load can get very local too - even knowing what the house down the road at the same elevation is built to doesn't necessarily mean that your house will be the same.  Our local town of Johnsville is about 3 blocks by 5 blocks but has a range of snow loads.

At 5000ft in the Northern Sierras they tried to persuade us to build to 150psf, but our area was not fully surveyed and legally it was 85psf.  We went for 120psf in the end, which means a 6x18 beam to support a 20' x 20' area of roof.  There is 4' of very wet snow on the ground right now, so I guess there's some justification.

Thinking about it, with a 6x18 I'm gonna be getting into the chainsaw-and-bulldozer end of framing.  I guess I'd better start rereading more of Glenn's old posts...

6 x 18--I wish!!  They want a 6 x 24 for my house, 30 x 16.
Title: Re: How to calculate snowload?
Post by: glenn kangiser on March 05, 2008, 12:10:31 PM
Had to look up Johnsville, davidj.  You are a ways above Drew.

Do you guys still drive Dodges up there?

(http://www.johnsville.net/images/Frank_Sobrero_deer.jpg)

http://www.johnsville.net/
Title: Re: How to calculate snowload?
Post by: davidj on March 05, 2008, 08:49:37 PM
Quote from: glenn kangiser on March 05, 2008, 12:00:49 PM
Don't forget the sledge hammer.
So much to learn!  (And so few bandages to sort out the incidental trauma).

Fortunately I went through the "be careful of things falling off the roof and onto your head" learning experience last Summer as I'm guessing a 750lb beam would raise quite a bump if dropped from 20ft up.
Title: Re: How to calculate snowload?
Post by: davidj on March 05, 2008, 09:17:05 PM
Quote from: glenn kangiser on March 05, 2008, 12:10:31 PM
Had to look up Johnsville, davidj.  You are a ways above Drew.

I think if you pop over the Pacific Crest from our place, then head downhill for 50 or so miles (as the crow flies) you'll end up at Drew's.  If you climb up the local peak on a clear day, you can just about see his  trenches (http://countryplans.com/smf/index.php?topic=3681.msg48581#msg48581), much as you see roman roads from the tops of hills in Europe...

Quote from: glenn kangiser on March 05, 2008, 12:10:31 PM
Do you guys still drive Dodges up there?

http://www.johnsville.net/

I'm guessing my neighbor probably still has that car on his lot (he's got most other pieces of machinery that made it to Plumas County in the last 100 years!)

Johnsville is a great place.  According to the census, population 21, median male income $0 and, rumor has it, more millionaires per head than any other town in California.  It's a historic preservation district and seriously expensive (for the middle of nowhere), but if you head two miles down "red dirt road" you can find lots for $20K/acre and displaced computer programmers yielding chainsaws, sledge hammers and very large bits of wood.
Title: Re: How to calculate snowload?
Post by: NM_Shooter on March 05, 2008, 11:17:08 PM
Take a look here:  http://www.alpineequip.com/upload/391/FELDMANNpg24252627.pdf
Title: Re: How to calculate snowload?
Post by: MountainDon on March 14, 2008, 04:17:33 PM
So you think you have snowload problems?

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/file009111111.jpg)

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/file008101010.jpg)

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/file005777.jpg)

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/file007999.jpg)

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/WOW111.jpg)

(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/file000222.jpg)

Watertown, NY area.
thanks to John (redoverfarm)
Title: Re: How to calculate snowload?
Post by: intelijoc on December 23, 2008, 02:24:14 PM
I called the building department- easy.  Mine is 125lb elevation is 11,600ft


intelijoc
Title: Re: How to calculate snowload?
Post by: John_C on December 23, 2008, 03:23:25 PM
Here is a pdf download where you can look up wind & snow load by county.  If the link doesn't work post a reply & I'll try to find the bug in it.  It's a large file... since it's for every county in the U.S.

www.chiefbuildings.com/design/MBMA2002.pdf (http://www.chiefbuildings.com/design/MBMA2002.pdf)

Title: Re: How to calculate snowload?
Post by: Redoverfarm on December 23, 2008, 03:44:34 PM
Hey John do you have the original site?  This one is Virginia.
Title: Re: How to calculate snowload?
Post by: John_C on December 23, 2008, 05:02:45 PM
Oops, my bad.  I changed the link above.  I downloaded the file months ago & renamed it, I had to search for it again and posted the wrong link.  :-[
Title: Re: How to calculate snowload?
Post by: MountainDon on December 23, 2008, 05:16:22 PM
That's a handy reference. I'm going to place it in a new topic under Referral Links.

Note that many locations in the west are site specific. The terrain in the mountains can cause grossly different loads in areas less than a mile apart, different sides of a peak/ridge.
Title: Re: How to calculate snowload?
Post by: phalynx on December 23, 2008, 05:30:22 PM
Don, those are some of the funniest snow pics I have seen..  I love snow, but I would imagine that would be a little "overwhelming"

Title: Re: How to calculate snowload?
Post by: Ernest T. Bass on December 23, 2008, 08:57:36 PM
Yeah, that's pretty amazing.. Though, last year there were some drifts that measured about 15 ft. deep just a little ways inland from us..  :o
Title: Re: How to calculate snowload?
Post by: glenn kangiser on December 23, 2008, 11:30:44 PM
Sorry but that snow is not compatible with life... [crz]