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Re: Tall stud wall framing / IRC rant

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MISLEADING.  I believe he was complaining because the table was MISLEADING--it *appeared* to be saying one thing, but on VERY CLOSE inspection it was *not* saying that, except in very limited situations.  IMHO it would have been much better for the body of the table to address the majority of the situations, with footnotes addressing the minority of unusual situations.

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 8/27/05 9:33:12 AM, smaxwell(--nospam--at)engin.umich.edu writes:

Jordan,

I am confused.

Why exactly are you ranting at the IRC/IRC folks?

Is there anything technically wrong with what is in the table (when
accounting for the limitations/footnotes) when compared with an
"engineered design"?  In other words, if you calc stuff out for
situation that meets the limitations that you listed (i.e. snow load of
25 psf or less, trib width of less than 6 ft, Fb less than 1310 psi [is
that supposed to be Fb, Fb' or Fb*?], etc), would 2x6s work for a 18
foot tall wall?

Is the table unclear?  And by this I mean that if someone reads ALL the
information in the table it reasonable to understand that they might come
to a different conclusion than someone else.  I don't consider something
unclear just because the limitations are not listed in big (24 point),
bold letter but rather in footnotes that might be small.

I guess that if I am understanding correctly, you issue is not that the
information in the table is wrong (at least that is not what you seem to
say), but rather than because is has such a limited practical use, it
should not be in the code cause in this situation it made your life
difficult because someone did not read all of it.  So because of that, you
want it gone from the code.

Let's look at if from the other side.  Let's say we get ride of it from
the code.  Now, say there is a project somewhere that is being designed
per the IRC (i.e. prescriptively) that DOES fit that criteria.  In this
situation, 2x6s would now NOT be permitted (this all assumes that the
information is technically accurate).  So, on this project the client
would have to pay for 2x8s when technically 2x6s would work.  Now, we have
just reinforced that good old mantra that contractors love to change:
"Boy, is this way over engineered" (whether true or not).

I guess in the end I am wondering if you want the IRC (and other model
codes) to put a big note in the front of the code in big, bold letters
that reads: "Idiots, this includes people who are otherwise smart that
just don't read all the requirements, shall not use this documents".  To
be frank, this would also put a lot of engineers out of business as there
are lot of people, engineers included, who don't always read all the
"instructions".

So, I think you should be ranting at the foreman and designer.  After all,
the foreman appear to have been WRONG.  The IRC apparently does _NOT_
permit the use of 2x6s in your particular case (you mentioned 30 psf snow
load as well as trib width of 17 feet, I believe)...altough s/he is
correct that there are situations (albit very limited) when the IRC does
permit it.

Now, if I am wrong in that you believe the information in the table (even
when factoring in the limitations) is inaccurate when compared with
a comparable engineered design, then maybe the code needs to be changed.

Regards,

Scott
Adrian, MI


On Sat, 27 Aug 2005, Jordan Truesdell, PE wrote:

> I had a meeting today in which  a residential foreman  argued that an
> 18' tall stud wall needed only be 2x6 studs on 16" centers according to
> the table in the IRC. Well, I'd had this discussion with the designer a
> week previous, where I showed him the output of an analysis that
> indicated a 2x8 was necessary for this framing. The designer also
> thought that 2x6 was okay, but didn't reference the IRC.
>
> I looked it up tonight, just to see if the IRC was sharpening their
> pencils a little much again, and found that the table, R602.3.1 to be
> exact, does indeed show 2x6s for an 18' stud wall.  Curious, I read the
> notes at the bottom and found the caveats listed to be almost
> ridiculously restrictive, such that the designs are practically unusable
> in a good bit of the country. Snow load must be less than 25psf - I
> assume this is ground snow load, since there is no formula in the IRC to
> convert to a roof snow load (locally we're 30).  Fb must be > 1310psi.
> Well, even with a repetitive and size factor added, No.1 SPF - the most
> common stud material around me (and on the east cost, I suspect) comes
> out to 1308psi. Add in an E of 1.6x10^6, and the list of lumber species
> and grades gets mighty short - #2 S. Pine and Doug.Fir are the only
> framing species that fit the criteria.  Here in the east there are no DF
> studs, and S.Pine smaller than 2x8 is found only in treated lumber and
> trusses without a special order.  Tributary width for vertical loads
> must be less than 6'.  Unless you've got lots of interior bearing, or
> are only checking gable end walls, that makes for pretty small rooms and
> no trussed roofs. And if it weren't obvious from the material
> properties, Stud grade studs are not permitted (nor are utility,
> construction, or No 3).
>
> It just makes me shake my head.  Even if this particular job didn't have
> a 17' horizontal span without a sole-to-top plate stud, and if they
> hadn't framed a two story wall by stacking two 9' tall walls, and if
> they hadn't used 2x4s, and even if it wasn't backing up brick veneer,
> there are still 5 different criteria that disallow the use of this
> chart.  And yet, the chart says 2x6 on 16" centers works, so they figure
> it's correct, and I'm full of *expletive* for telling them they should
> have used at least 2x8s. Worst, with their openings they'll need 3/4T of
> steel to fix the problem without packing the wall to thicker than
> 3.5".   It think the #2 S. Pine and Doug.Fir needs to be in the title,
> and they may as well just say "non-bearing-walls only", with a little
> note at the bottom for an exception for walls with tributary widths less
> than 6' and snow loads of 25psf or less.
>
> I know that moaning and complaining here won't get the code changed (and
> I'm honestly not sure whose ear to chew on to try and get it changed),
> but are the rest of you doing small jobs like this running into similar
> problems? If so, how do we fix the code language so that mistakes are
> less likely?  Even the best inspectors can't remember all the notes and
> subnotes across all of the disciplines in a couple thousand pages of code.
>
> Jordan