Ledger or Hangers For Addition

[jandlo]

I am working on a residential addition. The new floor framing will be higher than the existing by about 8" to 12". If it wasn't, I would just remove the rim joist, run the new joists over the existing wall and install blocking. But I don't want to interrupt the sill plate. Would it make sense to fasten a 2x12 Ledger to the existing studs, sill plate and rim joist with lag screws, and hang the new joists off that? Or would it be better to hang the new joists off the existing sill plate and add blocking as necessary to raise the hanger (image below)? Or as always maybe there's another option I'm not considering.

 

[phamENG]

Is there sheathing there now? Does it have to come off? If it doesn't have to come off, then do a ledger. If it's coming off anyway, then I could get behind what you're showing in your sketch.