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Re: Wind Load on Deep Snow Profile

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The code load case is 75% wind with 75% snow.  While, intuitively, the high winds should blow the snow off the roof depending on the fluffiness of the snow, the code doesn't allow you reduce the snow load less than 75%.
An old quote from a regulatory agency "Don't confuse reason with requirements."

On 6/11/08, Jake Watson <jake.watson1(--nospam--at)> wrote:
One other thought, as the wind presure increases, will it blow the
snow off the roof?  If the drift is parallel to the wind load, then
there is not an increase in area.  This is the typical case considered
in the code.  If the wind blows the other way, the drift is reduced.
The wind won't load the drift zone in the first place.  Any drift
caused by wind blowing the other direction will be moved again by the
new wind direction.

This really needs a picture.

Jake Watson SE
Salt lake city, UT

On 6/10/08, Paul Blomberg <paul.blomberg(--nospam--at)> wrote:
> I'm putting together design criteria and am curious how you handle / take
> into consideration the added projected wind surface area due to built up
> snow on the roof of a building?
> I have a new metal building going into northwestern Montana and the ground
> snow load is over 120 psf.  That is a relatively deep pile of snow.  When
> you put together your load case that combines snow plus wind, do you
> increase the projected profile of the building to reflect the height of the
> snow on the roof and the associated wind load?
> I normally include this additional snow profile to calc the wind loads but
> this my first heavy snow load situation where the increased load is
> significant.
> Paul.
> Phoenix, AZ

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