Stepped foundation wall to reduce rise from garage to house - joist on concrete wall new construction

[BakingFool]

My new home design calls for 11′ wide by 14’long entryway that sits between the living space and garage, at the same floor level as the living space. Floor support is 2×12 joists, and the exterior walls are 2×6 construction. There is a u-shaped stairway in the entryway to the full basement under the living area.

The house was designed with 8′ foundation walls, and had a rise from the garage floor to the subfloor of 17-1/2″: 4″ for vapors + 1-1/2″ sill+ 11-1/4″ joist + 3/4″ sublfoor. For multiple reasons (steps, topography, fill and grading) I would like to lower the living area and entry to have only one step up from the garage.

I came up with the idea in the attached diagram. The code I researched calls for a sill plate and bearing on concrete of at least the width of the studs. The minimum bearing length required for 2×12 joists is 1-1/2″. For the foundation wall between the entryway and garage I am proposing to use a 9′ high, 10″ thick wall, with a 4″ wide step at 8′. All other foundation walls will be 8′ even with the step at 8', except garage walls which will be 4′ frost walls even with the top of the 9' wall in the diagram.

I am interested feedback on this proposed solution. Any obvious problems with this plan? Thank you in advance,
Don

 

[BakingFool]

Not depicted in the diagram is the bottom plate of the stud wall would be on top of the pressure treated 2x6.

 

[BakingFool]

It just occurred to me that it might make more sense for the step in the foundation to be 11-1/4" high, and extend the subfloor over the 2x6 sill plate - assuming there are not other issues with this proposal.

 

[BakingFool]

I forgot - I can't use a 11-1/4" step, because the other walls would have to be 8'-0 3/4". Back to the proposal depicted in the attachment to the first post.

 

[jar546]

Let's start with the basics. Not only will you have more than 8' of unbalanced backfill on an 8" CMU wall, but there will be a garage slab with cars parked on it. Make sure that is taken into consideration when determining how much steel you want in the foundation wall. Consider a thicker wall on the garage side. Pennsylvania is full of cracked basement foundations where this was not taken into consideration.