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Re: Full height stud requirements in IRC2000/2003

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You are correct, and the answer is "you can't do it with 2x4 SPF studs". The issue is that, in this case, the garage is built, and has been built with 2x4s. I'm going to have the builder use SPF posts on either side and through bolt to get the stiffness. My concern is that on all but one of the houses built in this jurisdiction, I was not called by the owner to perform consulting reviews of the framing. Being sympathetic to the builder, I'd like to find where the building code references the proper design. My review seemed to indicate that there was no guidance, and all illustrations suggest that a single king stud (2x4 is implicit for <10' walls) is proper practice. Moreover, the building inspectors cannot impose a more stringent requirement than what is in the statewide (=ICC) building code (by law, in Virginia). I don't remember Scott's reference to CABO (I did little wood, and almost no residential when we were under CABO), but the concept is correct, and fits the prescriptive model well. Unfortunately, I can't find any reference to it in the IRC.

It takes three 2x6 SPF studs to take the wind load, fwiw. I always assume the jacks take the vertical load only, and the kings take the wind load only. It's not particularly accurate mechanics, but it simplifies the math and - as you pointed out - at $6 a stud, it doesn't pay for me to sharpen the pencil and spend an extra hour of time, just to save a dozen studs in a whole house.

Also, I recommend 2x6 studs to all my clients who want walls taller than 8'. At 9', the deflection of the walls are too great for anything but vinyl siding. We only need R15 or R16 here (5500HDD or less) depending on the jurisdiction, so many builders will use high density 3.5" batts and add a layer of XPS to get the extra when needed. They (the builders) moan and complain all over the place about it, too. The table in the IRC (which, I'm ashamed, I did not comment on before the end of March this year) is terribly misleading. It is the only table which requires the use of S. Pine #2 or DF #2, but doesn't actually call out the species and grade, it's the only table which doesn't list 30psf/50psf as the snow load, and the limitation of tributary area above the wall makes it suitable for only non-loadbearing (i.e. gable end) walls.


Daryl Richardson wrote:


       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?


H. Daryl Richardson

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