Wall height question IRC 2018

[Dan_Shade]

Not a timber frame question, but I didn't know where to post...

I'm building a 32x64 building and have confused myself reading the code requirements.

I want to put a 12' tall 2x6 wall (sheathed in 7/16 osb) on top of a 20" tall block wall.  Some areas of the code look like its ok, other areas say max stud length for load bearing wall is 10'.  I'm looking at R602.3(5) and R602.3(6)

[Don P]

I'm betting that we are not talking about a residence, that is the prescriptive residential code for habitable buildings. Correctly you would probably be in the construction code. But let's see if you can get there prescriptively.

It does look like that section has been rewritten, somewhere in the footnotes it used to limit those tables to 12' wide building sections, effectively useless. I'm seeing a remnant in R602.3.1 exception 2, however, reading exception 3 should get you there.

[Dan_Shade]

The building will not be a residence. 

County inspectors use irc 2018.

I'll give them a call to make sure I'm on the correct path. 

Thanks 

[Don P]

I doubt it'll go there but just in case as a note for later cause I'll forget this path.
Curiosity got me, and I had both codes open on the computer. The table in the construction code looked the same as in the residential code. I then looked in the code referenced WFCM, Wood Frame Construction Manual and again bumped into the 10' prescriptive max height. Looking for the reasoning I opened up the commentary to the prescriptive section of the WFCM (these are I think also downloads at awc.org) Starting on pg 113 is a design procedure if needed (with examples, woohoo!). Basically take the tributary area of a stud, calculate and apply the design wind load, check bending and deflection at that stud length.

*Referenced Standards are part of the code... diving deeper than most inspectors have been, go to chapter 44 of the IRC "Referenced Standards" scroll down to AWC (American Wood Council) click on that and among other titles the WFCM will show up there. This is the kind of path to show an inspector when, although what you might be proposing is not in a prescriptive table, it is designed according to "accepted practice" through the use of a recognized referenced standard. 

The next question to run down is about the 20" tall block wall that is laterally unsupported at the top, there's always something.