Trex to replace PT
I have a 20x14 PT deck. I'm switching to Trex. I decided after buying the decking, I should also do the Trex Elevations so the decking doesn't get wavey due to the imperfect wooden joists. I have 4 posts since my current 2x10's span the 14 ft. The deck is only 6" off the ground if that so a drop beam is not possible. The header beam (opposite the ledger that the joists go into) is currently two 2x10's that the joists run into (no cantilever). On to my questions.
If I go to Elevations and start over...they are 8" joists. So I need an 8" ledger. Should I put the new elevations ledger ON the existing ledger or replace it all together?
Back to the header beam, same thing. I assume I should replace it with the Elevations beam? Should I replace it with 2 beams or would one suffice? If two beams, should I bolt them together like I did the wood? Since these won't warp maybe I don't need to do that or just bolt it in a few places so it doesn't slip?
I'm also picture framing the deck with surface mount posts as railing (I think). Surface mount posts need support underneath so I figured I'd add a steel block (horizontally though) flush with the joists for the post to grab onto. Anything wrong with that logic?