Trying to come up with a covered, screened porch flooring solution for a new build. The porch is about 8’x54′ (long covered porch across the front of the house). The porch “frame” is already built, and is a lot of 2×12 TYP with everything 16″ OC or less. The bottom of the frame is about 3′ above a concrete foundation. The walls below the frame are CMU block with about ten 8″x16″ vent openings. The porch can be further stiffened with the addition of pony walls if needed, so frame stiffness is not a big factor.

I have about 3″ of “thickness” to play with. The finished floor will hopefully be brick pavers, 3/4″ to 1″ thick depending on which ones I go with. So that leaves 2″ for the subfloor sheathing, membrane, grout, etc. I’ve read about treated plywood (but it delaminates), Advantech subfloor (that isn’t rated for this), Advantech subfloor that has been covered with a paint-on water seal (but still not rated for this), cement backer board over plywood, etc.

What’s the best system for this, or is 2″ of thickness not enough? The house is in climate zone 2, about fifty miles south of Houston, 10 miles from the coast.

Thanks,
Ira