The old plywood was removed because it was uneven. Possibly something to do with the fact that this house is on brick columns that are about 3' tall. It does not have a concrete slab foundation. What needs to be under the plywood (either masonry or bricks) to make it flat and where does it go? How many columns? Do I then Tapcon the plywood to the columns? How do I attach the plywood to the rest of the house?