CMU basement wall with unreinforced courses at top

[jandlo]

I have a situation where CMU basement wall at a residential porch was construction using 12" block with #5 bars @ 48" OC. There is a bond beam at the top of the 12" wall and then two courses of unreinforced 6" block aligned with the inside face of the 12" block which will be above grade and provide a ledge for 6" stone exterior. The diaphragm is a concrete slab. My assistance was very limited so I didn't detail the wall. I anticipated reinforcing on the inside face to extend through the 6" block and lap the slab dowels -- treating it like a typical basement wall. It turns out that the bars were near the outside face of the 12" block, did not extend through the 6" block, and the dowels were either not installed or only have a 4" leg into the 6" block (hence the addition of the angle sketched in below. It's a typical residential basement -- retaining about 7' of soil. I just don't like the transition from 12" to 6" block without reinforcing. The way it's constructed it might behave more like a retaining wall than a basement wall, but the 2'x2' wall footing with minimally dowelled in vertical bars probably don't do enough to prevent rotation.

Any suggestions/thoughts on if this might work as is or inexpensive ways to supplement? I was thinking of adding lengths of metal strap vertically in-line with the rebar on the inside face from the top of the wall, and across the block transition to provide tensile capacity to the location.

 

[phamENG]

1) A lintel block is not a bond beam block.
2) Do you have any direct tension on the masonry here?
3) This is going to be an area of very low moment. If the answer to 2 is no, then just check it as unreinforced masonry and see if it works. For residential, I always design as unreinforced and then switch to reinforced only if needed. Residential contractors so rarely get the reinforcing right, I sleep better knowing that unreinforced is good. If you designed it as restrained basement wall, then you would have assumed a pin at the top and bottom anyway.
4) Is the rest of the house already built on top of it? Any room to have them drill down into it and epoxy dowels in now?

 

[TRAK.Structural]

pham makes good points above. Out of plane shear to transfer the wall reaction to the slab diaphragm would be my biggest concern. checking the shear stress as unreinforced might work but you'd need to have some idea on the type of mortar they used in order to pull the right values from TMS, could be a tough ask for residential work in my experience. Dowel some #4 bars into the grouted cells and sleep better.