I have 5/4 fir boards that were used to make up columns that hold up the front side of my 8x10 front porch. These columns rest on the 3/4 t&g fir deck boards, which were not nailed to joists and run parallel to the house, not perpendicularly. I must replace the columns. I want to use PVC, load bearing quality columns. As the joist system rests on top of the brick piers, should I run the new columns to the top of the pier, or use a standoff on the pier anyway? Or, just mount the pvc column on top of the deck boards, as originally done? It seems to me, due to wood movement (temp variations and humidity swings are great in va), I should fix joist system, run deck boards perpendicular to allow drainage, and run posts down to brick pier and build deck boards around post column allowing 1/2" gap? Any advise on proper way would be appreciated!!!

If the posts that were done when house was built worked, why worry about bringing the post down to the piers?

I would not go through all the effort to over think this. Simply let the new post rest on the deck. Just be sure that the load is being carried through the floor joists to the piers and not by just the flooring alone.

I should have mentioned that the posts have rotted at their bases, as has a couple of the t&g decking boards on the outer edge. The porch faces north and gets little sun.