IRC Braced Wall Line - 20ft rule

[Ben29]

I have a potential client who wants to install (3) 4ft wide windows in the rear wall of his existing house. I cannot get this to work because it removes the braced wall panels at the corner of the house and the next braced wall panel will be 22ft from the corner.

The client is open to installing an interior wall beyond the corner of the house in order to add back the braced wall length he wants to remove. But I still have the issue of the 23ft opening between braced wall panels.

Where does this 20ft rule come from? Should I use engineering judgement to supersede this rule?

 

[Flotsam7018]

I don’t know where the 20ft comes from, like a lot of things in the IRC. Likely from some combination of historic and anecdotal precedent.

I would just abandon the IRC and do an engineered design, should be pretty simple if you can add that interior shear wall.

 

[XR250]

Meh, I ignore that rule frequently

 

[Flotsam7018]

If you’re only modifying that one BWL why not just do a flexible diaphragm analysis and design a shear wall? If you’re hand waiving the prescriptive requirements then you’re just not doing lateral design of any kind.

Of course, you’re free to use your judgement as you see fit.

 

[BN4537]

The 10' from the end and 20' "rule" in the IRC is entirely to make it easy enough for a contractor to figure out how to brace most houses without using an engineer and without really having to understand anything about shear wall calculations. It's not the only answer by any means, it's just the least complicated and easiest to explain.

I concur with abandoning the IRC and just going with engineered design.

 

[TRAK.Structural]

If you are adding back a new wall of the length shown in your sketch I think there should be plenty of stiffness/strength and I wouldn't get too hung up on that requirement.