Thanks to sierraeast for straightening my goof-up out & Bill,that's a pretty good detailed work-up about what I've got planned. I'm going to study it at length,but you confirmed my basic original thoughts about how to accomplish this. Your charts and guidlines will be very helpful as I fine tune this. The point about installing the panel in the garage/interior wall cavity was a great heads-up....I was going to do just that. If I surface mount the sub panel in the garage on top of the firerock(perhaps in a firerock plenum) then I should be OK ? I had planned to run all the garage wiring in conduit anyway. I should add the additional rooms(12' firewall between the garage/shop & living area) will be 8' ceiling height in an area that is 12' tall(this leaves a 3&1/2' loft/storage area above those rooms). This will also make those areas easier to wire/insulate/& run HIVAC plumbing. Thanks very much for the information.... back to the drawing board..LOL...Dave

Yes, as long as you've go the load issues right, there's no problem running a sub from a sub. My house will have six panels that are effectively subpanels off the main subpanel which is distinct fro the Service disconnect.

Thanks for everyone's input. My main panel has 30 spaces and allows a maximum of 40 circuits. It already has the full complement of slimline breakers and is maxed out at 40 circuits by the builder. I'll need to move a few circuits over to the sub-panel to make room for the double pole 70 amp feeder breaker. By the way, the main panel is rated at 200 amps and I calculate my current home load at 87 amps, so I have plenty of capacity available for the 40 or so amps I intend to use from the sub-panel. Dave

OK USE-2 is one of the service entry cables. You don't need to enclose it in conduit except where it needs to be protected. If it goes somewhere where it needs to be protected from damage, then conduit (or similar) is required. As near as I can tell (going through wood joists in your post) conduit isn't required. HOWEVER, you can not run the ground as a separate wire. You're either going to have to get cable with the appropriate number of conductors or run conduit and individual conductors.