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Re: Question for the snow gurus

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This is pretty close to what is obtained using the UBC formula.  Now
you have me curious.  I'm wondering if the other systems I've seen 
are being designed, or just put on randomly by the contractor.  They
don't look stout enough to contain the kind of forces I'm obtaining.

The architect has specified ice and water shield from the eave up to 3 ft.
from the ridge under the shingles.  Any experience with this causing a 
problem?

Thanks,
Dan Goodrich, P.E.
Utah

> Dan,
> 
> You should design for the weight of snow to be contained times the sine
> of the roof slope (5/13 in this case) because, under critical thaw
> conditions, all of the snow will try to slide off at once.
> 
> A word of caution: don't do this unless you are using a membrane
> roofing.  If you have shingles you can expect the contained snow to
> cause an ice dam which in turn will cause water to back-up under the
> shingles and leak large volumes of water into the building.
> 
> Regards,
> 
> H. Daryl Richardson,
> Calgary
> 
> > Dan Goodrich wrote:
> > 
> > I've designed a ski lodge where the snow load is 150 psf on a
> > 5/12 pitch roof.  The owner has asked about putting log railings
> > on the roof to help keep the snow on the roof, and not on the ground
> > in front of the windows and doors.  I am trying to determine what
> > force
> > to design the connection to the roof system.  UBC Appendix 1648
> > gives a force to design for vertical obstructions.  However, this
> > seems
> > very excessive, especially when compared to what I've observed on
> > other roof systems.  Anyone know of any other guidelines to follow,
> > or procedure?
> > 
> > Thanks,
> > Dan Goodrich, P.E.
> > Utah
> > 
> >
> 
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