Anyone know of a framing detail that shows the 2nd floor joists being hung inside the 1st floor walls?  I mean, instead of placing the joists on the 1st floor top plates with a rim board; hang them from a ledger on the wall.  Would require a little taller wall but sure would make insulation/air sealing more effective I think.  Thanks.

From an engineering perspective it is not the ideal. Of your 3 choices(compression, tension or shear), shear is usually the least desireable mode of attachment. The load capacity and integrity is entirely reliant on the fasteners ability to maintain a grip in the wood... Long term...

I've seen it done with 2X6 walls, which is the minimum I would personally use for stick construction. Simply notch the 2X6's to hold the ledger. Then the ledger is in compression. Our ledger for our floors is bolted on the inside of the ICF walls (shear), but those are 1/2" bolts, embedded in concrete.

Mine is ICF, so like jbebree my floors are hung inside the walls. I used top mount joist hangers on the ledger, and I suspect you could use those on the top of a wall to hold the joists, however I'm going to guess that you will have less trouble with trades and inspectors if you frame conventionally, then follow up with a flash of closed cell foam to air seal the rim. I also suspect that if you don't do it conventionally that you will need an engineer's stamp on it.

Icf using Watkins hangers. The floor system is inside the walls without a band joist. No top plate either using raised heel trusses set between the walls not on top using the same hangers. Old school framing has balloon framing with the floor hung from the studs.

Yep ICF here also, but I went with a inward corbel ledge(and a wall thickness change) to support top chord open web trusses without the shear of a ledger board and anchor bolts. I am also in a seismic zone so additional fixtures were required anyway to develop tension with the floor diaphragm, and this is a little more of a problem with anchor bolts and a ledger...

For conventional construction, Top chord hung trusses would be one way to make the rim less of a sealing issue yet still keep the floor loads in compression on top of the wall...

While the Watkins work for ICF, my situation is regular 2 x 6 framing. I agree that a top hung hanger would be the best, but that will still require a ledger (still in shear). Not aware of any hangers that would accept, say a 11 7/8 TJI and allow fastening to a stud member through the wall side flange. Maybe Simpson could get to work on that .

Notching is a interesting idea; and I wondered how balloon framers did it back in the day. Must be a detail somewhere. Thanks.

The traditional balloon frame was 18' studs framed on the ground, raised into place then the floor joist were nailed to the studs at the required height. No ledger. I last saw this used on a local house 25 years ago. Of course they used 3/4" plywood t&g sheathing, not osb.

You can let in a ledger into the walls studs under the joists for floor joist support. Some of the older houses used a 1x4 there, but a 2x6 would be better. The floor joist is then nailed to the stud.

Price it out.....you will decide against doing it. Brackets are expensive and its labor intensive.