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Re: Tall stud wall framing / IRC rant

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Shame on the IRC for even providing a table that is so
exclusive, yet gives the impression at first glance
that it serves a useful purpose.  They could stand to
provide a big bold statement in the front of the code,
summarizing the most critical limitations to
prescriptive design, rather than burying a bunch of
small-text footnotes throughout the various tables and
figures.

Builders would have you think that the IRC provided
way too much information.  I would argue the opposite.

I'm sure this is common, but around here, builders
often frame 9ft walls with 8ft studs and knee walls. 
And how many A-frame structures with full window walls
are erected here in Pocono vacationland?  They are
being built here everyday with stacked studs and NO
structural horizontal plate.  They don't even realize
that the design table exists, not to mention not
having a copy of the IRC.

Jim Wilson
Stroudsburg, PA

--- "Jordan Truesdell, PE"
<seaint1(--nospam--at)truesdellengineering.com> 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
> 
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