Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Sloped Roof snow load

[Subject Prev][Subject Next][Thread Prev][Thread Next]
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
Engineering and Design
206 Peek Street
Jackson, CA 95642
p (209) 223-0381
f (209) 223-0716
e terry(--nospam--at)
From: Pinyon Engineering [mailto:Pinyonengineering(--nospam--at)] 
Sent: Monday, July 21, 2008 9:24 AM
To: seaint(--nospam--at)
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)>
To: <seaint(--nospam--at)>
Subject: RE: ASCE 7-05 Section (#4) clarification needed

This is a multi-part message in MIME format.

Content-Type: text/plain;
Content-Transfer-Encoding: quoted-printable

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

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

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

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


This seems to conflict with itself. My first interpretation is that if =
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 =
section of the statement reads =93regardless of actual roof slope=94 in =
case I would interpret the 20% of the Snow Load exceeding 30-psf to be =
to any sloped roof.=20


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


Dennis S. Wish, PE


Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

La Quinta, CA 92253



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: 
******* ****** ****** ****** ******* ****** ****** ********