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Re: Full height stud requirements in IRC2000/2003

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Jordan,

       I don't know about your codes but it seems to me that

1.)  you have wind loading on your door;

2.) you have reactions from that wind load that are applied to the studs at the side of the doorway either directly or via the door header;

3.) and that the stud(s) at the side of the door must resist the applied loading.

I would expect that a single stud would not be adequate!! I would expect to see at least THREE studs for a 2x4 wall and TWO studs for a 2x6 wall. Note: these would be full height studs in addition to the two cripples (to get 3" of bearing) under the header.

What do studs cost in your neck of the woods anyway? Six or seven dollars each?

Regards,

H. Daryl Richardson

----- Original Message ----- From: "Jordan Truesdell, PE" <seaint1(--nospam--at)truesdellengineering.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, June 27, 2006 11:26 AM
Subject: Full height stud requirements in IRC2000/2003


Does anyone know if there are any requirements for the number of full height (aka "king") studs in residential construction in the IRC (2000 or 2003)? I just ran across an installation with a 16' wide rollup door in a 10' tall 2x4 stud wall, with double jack and single(!) king studs. I'd like to reference an IRC provision that prohibits such an assembly, but it appears from my reading that there is no requirement that a jamb must have more than a single full height stud, regardless of opening size. The WFCM has a check for king studs, and a quick glance at one example showed that the number required appeared to be in line with what I'd expect from bare calcs, but there doesn't seem to be any mention of this in the IRC. Am I missing some obscure provision that's not in the wall or floor sections? The floor section lists header sizes with the number of jack studs necessary, but no mention of the king studs required.

On a side note, is anyone aware of some testing which was done to come up with the allowable stud heights in the IRC? The data they have does not match the NDS requirements, and I'm curious whether the tables were developed by engineers, some destructive testing research, or the NAHB lobby. Checking the walls using the table R602.3(5), supporting roof and ceiling only, 10' tall SPF studs @ 24" o/c, I get a deflection of L/96 and an Es3.9-3 combined stress index of 1.81 with a 24' rood truss and 17.8psf wind (90mph gust, zone 4, exposure C, 33.3SF EWA - well within the applicability of the IRC). At 24" o/c, the 1.5/1.15 increase in strength allowed in the IBC 2306.2.1 doesn't apply, and even if it did, the combined stress would be still be >1, and there is no acceptable criteria for wood walls which is less than L/120 in section 1604.3 of the IBC.

--
Jordan


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