2nd Floor Design Question

I am a first time owner/builder desiging a high-posted cape house built with sips. I am shooting for a Shaker style interior with heart pine floors, peg rails, 11 in. mop boards, etc.. I would like to have a plank and beam 2nd floor built using T&G 2x6 or 8's nailed to beams 2'9" oc. My plan is to balloon frame with the sips (12') from foundation to eave giving me 8'on the 1st floor, 12" allowed for the 2nd floor deck and a 3' knee wall from the 2nd floor to where the roof line will start. My question is would it make sense to "ring" the inside of the sips at 8' high with beams (I'm thinking 4x12's) supported every 8' or so by posts? My plan is 25 x 33 and I intend to have two carrying (?) beams dividing the 33' dimension into thirds thereby giving me 11'(+/-) spans for the joist beams. The center 11' span will be mostly open to the 2nd floor except for the front 1/3 of that center 11' bay which will be floored in effect giving me a "U" shaped 2nd floor deck. If after reading this you are totally confused...join the club.

Thanks..glad I found this forum,

JP

Yep I'm confused.

Are you talking about having a free-standing structural frame that you attach the SIPS to?

Sorry for the confusion pegs_1,

Yes, I want to have the 2nd floor deck as a "stand alone" structure not sitting on the SIPs for support but using posts on the inside of the exterior walls to support the rim joists/beams. My plan is to then screw the panels from the outside into the rim beams.

JP

Still not sure I understand your question.

But if you build an average frame structure you will already have girts around the eave wall perimeter at the first floor height and and another eave girt at the top of the kneewall. I don't quite understand why you would need to add the 4x12 "ring". Also 12" is more than you will need for the second floor. 2x6s are probably more than you will need too if you are planing on laying a floor over the timber floor trusses. They aren't structural from a span point of view. More like a spacer.

Just to be clear. You would have about a 5x8 (depending on span and floor load) floor truss visible from below on the first floor, covered with 1x6 T&G, then 2x8 spacers run the same direction as the T&G over the floor trusses. Then sub-floor or planking whatever you prefer as flooring on the second floor.