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Re: Question for the snow gurus

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I found the article you mentioned online at:
http://www.nrc.ca/irc/cbd/cbd228e.html

It backs up what you have been saying very
nicely.  Thanks.

I should mention that all of the entrances to the
building are protected by gables.  I've found
several different snow brackets that might work
for the remaining areas of the building.

Thanks to all those who helped.

Dan Goodrich

----- Original Message -----
From: <h.d.richardson(--nospam--at)home.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, June 28, 2001 4:52 PM
Subject: Re: Question for the snow gurus


> Dan,
>
> No, I don't have any experience with this type of roofing system.
>
> My experience is limited to structural only.  I have designed a few
> buildings with snow loads in the 100 to 200 p.s.f range but all of them
> have either been (nearly) flat or much steeper than 5/12 to remove snow
> before it builds up to this level.
>
> I do know of one fatality from snow sliding off a roof.  As I recall it
> was in or near Revelstoke, B. C. several years ago.  A small child went
> missing and was subsequently found under the snow from the roof.
>
> It's common for buildings (mostly pre engineered) at industrial
> facilities to be equipped with "ice rakes" or gable canopies above
> doorways to protect employees against falling ice or snow.  The snow
> loads I have experienced with these is more like 40 p.s.f. or less.
>
> There is a publication by National Research Council of Canada, in their
> Canadian Building Digest, Division of Building Research, on this topic.
> It is CBD 228, Sliding Snow on Roofs.  It won't tell you much more than
> I have already; but it will some formal back-up if you need it.  Their
> address is
>
> Division of Building Research,
> National Research Council of Canada,
> Ottawa, Canada. K1A 0R6
> I do not know their e-mail address or their telephone number.
>
> I hope this helps.
>
> Regards,
>
> H. Daryl Richardson
>
> Dan Goodrich wrote:
> >
> > 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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