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Garage Stem Walls Under Braced Wall Panels

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XR250

Structural
Jan 30, 2013
6,017
Around here (central NC), most garage foundation are built with 4" brick/4" CMU or 4" brick/8"CMU. The stud walls generally bear on the brick portion. Yeah, I know this is not ideal, but this is how it is done and it seems to work fine. Unfortunately, this is at odds with the IRC as far as stem walls under braced wall panels go. See the attached drawing. The upper detail is from the IRC and shows the brick as a water table with the studs bearing on the reinforced CMU. The lower details are how it is normally built. The field inspectors do not know this portion of the code well so this gets swept under the rug in almost all cases. The Architects and Builders do not want a water table detail. Does anyone have any suggestions how to build a stem wall that meets the needs of both the IRC and the Arch/Builders?
In some cases I have used a 2x8 stud wall and busted out the face of the 8" CMU top course to get some anchor bolt purchase (also shown on drawing)

Thanks!
 
 https://files.engineering.com/getfile.aspx?folder=8da9931b-0b48-47e1-9661-f3b9f4774503&file=STEM_WALL.pdf
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Ughh... I see what you mean. If you truly engineer the thing, you don't have to comply with IRC, right?

This is surely just my own ignorance but, can they really embed anchor bolts in brick like that and have a quality end product?

 
KootK said:
Ughh... I see what you mean. If you truly engineer the thing, you don't have to comply with IRC, right?

Correct - hence my 2x8 stud wall method. Builders are OK with it on the front wall of the garage where it does not add much material but frown upon it in other braced wall areas. I usually let the other walls slide (no pun intended) as they are typically very long without openings.

KootK said:
This is surely just my own ignorance but, can they really embed anchor bolts in brick like that and have a quality end product?

Welcome to the South! Yea, it is kind of a joke how these things are built.

Another similar issue is using a 2x4 wall on a monolithic slab. Most of the times, the bolts end up with about 1/2" of side cover!

 
We have been conditioned to think of brick as a non-structural veneer. I think that is mostly good practice, but in this case, from a strictly engineering mechanics point of view, I think an anchor embedded in the brick masonry is perfectly legitimate, but the problem is I think it would have very limited capacity because of the thin 4" wythe of brick. Then, even if you could develop a decent amount of anchor capacity, you would need quite a bit of 4" brick masonry to provide the dead load to resist the pullout. So, for those reasons, I don't think anchoring to the brick masonry works in practice. Not to mention the practicalities of constructability, how do you even embed a j- bolt in a single wythe of brick?... I guess with some creative chipping and of brick units?
 
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