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Re: retaining snow loads

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This a real live question.  I had occasion to inspect the damage done to the side of a pre-engineered building after our famous '96 snow storm here in Victoria BC.  What was of interest to me is that I had, previously, strongly recommended that a heavier gauge section be placed along the bottom of the cladding (there being no foundation wall between column footings: this is a riding stable) instead of the supplier 'z' light gauge section.  Sure enough, 12ft of snow from drift and slide-off from the roof pushed the cladding in about 2ft!!
What lateral force from snow?  I didn't do any numbers that time but I have since then considered using the normal "soil pressure" type of distribution with modified 'K' factors while the snow is dry and assume that it acts like a fluid until it either compacts under its self weight (which is probably the failure mode) or until it freezes at which time there may even be expansion of the mass.  Since the cladding in the case I inspected was normal industrial cladding on girts on columns etc at the usual spacings my guess was that the snow had exerted a significant force during its accumulation not unlike a hydrostatic force.

Thor A Tandy P.Eng, MCSCE
Victoria BC
e-mail: vicpeng(--nospam--at)
-----Original Message-----
From: Jeff Smith <smthengr(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Thursday, September 16, 1999 11:46 AM
Subject: retaining snow loads

Can anyone tell me how to apply lateral loads due to snow. For example, if
you have 10 feet of snow against walls and or windows, what forces (if any?)
should the wall framing and for that matter window glazing be designed for?
I have never actually seen snow build up against glass since the temperature
difference usually keeps the snow off the glass.


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