Sill plate on foundation - lack of full bearing

[TonyES]

We have a 12" thick wood framed wall which structurally only needs to be a 2x6 wall but due to desired insulation values the architect is wanting them as 12 inches thick. The contractor does not want to pour a 12" thick concrete wall, rather he wants to do an 8" ICF wall with 2" of insulation on each side of the concrete icf wall. Thus my 12" bottom plate is sitting on 8" of concrete and 4" of insulation. I see a potential for cross grain bending but at the same time if a 2x6 wall is strong enough for the relatively small axial loads than are we ok??
thanks for the thoughts/input.

 

[jayrod12]

Technically you can overhang wood studs up to a third of the depth. However I don't believe they had a 12" deep stud in mind at that point.

I wouldn't be overly concerned. You could provide a 2x6 bearing sill at each level in line with the concrete wall in an attempt to only activate portion of the wall directly on the concrete.

Another way I've seen this sort of this done was a client had 12" deep studs (vertical trusses) built by a truss mfr that only sat on the concrete and the rest of the stud (vertical truss) cantilevered out.

 

[KootK]

Two concerns for me:

1) is there a sheathed diaphragm on the studs that needs to make it's way back to the sill plate somehow? You may need a 12" plate on top of your 6" plate.

2) it feels as though you would be encouraging longitudinal shear splitting near the ends of the stud.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

Upon re-read, I see that you're already intending to have a 2x12 sill plate. I guess, if there's diaphragm shear involved, that makes perpendicular to grain cracking that much more important. Also, scratch my second point. We deliver axial loads to studs via portions of the cross section all the time without incident (truss connections etc).

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[Ron]

Stop letting the contractor dictate design! Tell him what you expect then require
it.

The overhang could be accommodated structurally but there are waterproofing and flashing considerations that will lead to deterioration of the overhanging portion.