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Re: Snow Drift Loading.

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One from Arizona really shouldn't enter into this subject, but it is 
interesting.

As a child, being born and raised in New York State, I recall the "snow 
fences" put up alongside of highways every fall and removed every spring.  
The "snow fences" were put up to prevent snow from drifting across the 
highway as drifts build up on the *windward* side of an obstruction, not on 
the lee side.

Now, if building up the roof of the existing smaller building is to cause it 
protect the newer building from drifting snow, then that would work.  
However, the newer building, being taller than the smaller building will 
protect the smaller building from drifting snow as the smaller building will 
be on the lee side of the larger, newer building.  Roof slope, as I see it, 
has little to do with snow drifts.

Now, if the concern is about sliding snow, then that is a different question.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Others wrote:

[Michael Bryson]

Correct me if I am wrong, but I think the original question was trying to
ask if you can reduce your snow drift caused by snow build-up against the
new building's walls (i.e. reduce hd in Fig. A-16-4). It is my opinion
that if you built a sloping roof profile matching the drift surcharge
profile (ie slope=hd/Wd) then the drift surcharge would equal zero. This
is because drifting is caused by wind blowing dry snow around, and the
snow doesn't care if it blows over a roof or existing snow. Hence, there
is no snow build-up. 

On Wed, 21 Jun 2000, Jake Watson wrote:

>       Only to an extent will it work.  Snow loading can be a big deal here 
in > Utah.  If the roof slope is steep enough you can take load reductions. 
> But as a rule of thumb, this won't eliminate the problem.  At best it
> will only lessen it.  If you raise the old roof above your new one, you
> won't have any problems.  See the appendix to chapter 16 in the back of
> the UBC for general guidelines.  If you are unfamiliar with snow
> loading, make sure you talk with someone (read building official) who is
> familiar with the area and snow provisions.  Where are you planning on
> building?
> 
> Jake Watson, E.I.T.
> Salt Lake City, UT
> 
> One last though, the drifting on the existing building won't have to be
> considered if they are far enough apart.  I don't have the provisions if
> front of me, so look at the appendix.
> 
> Pat Ebner wrote:
> > 
> > A project manager just came in and asked if I had ever heard of basically
building a sloped roof on a lower building to eliminate the snow drift load. 
He has a building which is to be built next to a shorter existing building,
which was not designed for a snow drift load.  I have not heard of anything
like this.  Has anyone done this or knows if this would work?
> >