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RE: Sloped Roof snow load

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Hi Tim;
	Slope reductions are better explained mathematically in the
commentary of ASCE7-05 at section C7.4 on page 326.  We have been using
?Cold Roofs with Ct=1.1? and for ?unobstructed slippery surfaces? since all
(well ALMOST all) of our roofs have metal roofing.  Alpine County has been
allowing this (although your roof has to be higher than 15? to use the slope
reduction).  I?m not sure what Mono County had been doing.
	Good luck and take care,


Terry Weatherby
Weatherby-Reynolds-Fritson
Engineering and Design
206 Peek Street
Jackson, CA 95642
p (209) 223-0381
f (209) 223-0716
e terry(--nospam--at)wrfed.com
i http://www.wrfed.com  
________________________________________
From: Pinyon Engineering [mailto:Pinyonengineering(--nospam--at)hughes.net] 
Sent: Monday, July 21, 2008 9:24 AM
To: seaint(--nospam--at)seaint.org
Subject: Sloped Roof snow load

In ASCE7-05 it seems the sloped roof snow load is the same as the flat roof
snow load except for a few extreme roof slopes no reduction for the typical
6:12.  Is this what others are finding?
 
Tim Rudolph
Pinyon Engineering
Bishop CA
 
 
From: "Scott Maxwell" <smaxwell(--nospam--at)umich.edu>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: ASCE 7-05 Section 12.14.8.1 (#4) clarification needed

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I interpret this as if the flat roof snow load (Psubf) exceeds 30 psf, =
then
you take 20% of the FLAT roof snow load (Psubf) and add that to the =
seismic
mass.  You do NOT take 20% of the SLOPED roof snow load (Psubs)...that =
is
the "regardless of actual roof slope" part.  And you do NOT take 20% of =
the
portion that exceeds 30 psf.
=20
Thus, if you have a 40 psf flat roof snow load and a 12:12 roof pitch on =
a
non-slippery roof such that the sloped roof snow load is 24 psf, then =
you
would add 8 psf (20% of 40 psf) to the seismic mass...NOT 4.8 psf (20% =
of 24
psf).
=20
Regards,
=20
Scott
Adrian, MI

-----Original Message-----
From: Dennis Wish [mailto:dennis.wish(--nospam--at)verizon.net]=20
Sent: Saturday, July 19, 2008 9:56 PM
To: seaint(--nospam--at)seaint.org
Subject: ASCE 7-05 Section 12.14.8.1 (#4) clarification needed



I need an interpretation to note number 4 of ASCE 7-05 Section 12.14.8.1
which states:

=93Where the flat roof snow load, Pf, exceeds 30 psf (1.44 kN/m^2), 20 =
percent
of the uniform design snow load, regardless of actual roof slope.=94

=20

This seems to conflict with itself. My first interpretation is that if =
the
snow load for a flat roof (say =BC=94 in 1-foot) slope or a shed roof =
exceeds 30
psf then you would add 20% or 6 psf to the roof dead load. However, the =
last
section of the statement reads =93regardless of actual roof slope=94 in =
which
case I would interpret the 20% of the Snow Load exceeding 30-psf to be =
added
to any sloped roof.=20

=20

How do others interpret this statement. If the roof is flat should 20% =
of
any Snow Load be considered whereas only 20% of the Snow load exceeding
30-psf be used if the roof is pitched?

=20

Dennis S. Wish, PE

=20

Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

La Quinta, CA 92253

dennis.wish(--nospam--at)verizon.net

http://structuralist.wordpress.com

http://www.structuralist.net

=20


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