Our neverending house renovation project has progressed to an enclosed front porch.  The porch is heated, about 7 x 20 feet, has a perimeter concrete block wall to the footer.  The framing is 2×6 and, unfortunately runs the long way with a doubled 2×6 running the short way to split the 20 foot span into a 7 and 14 foot span.  The current floor is self adhesive tiles over 3/4 inch ply over the original 1×3 (?) flooring (probably Douglas Fir).  Beneath the porch is a crawl space about 30 inches high with a dirt floor and a lot of old debris (big rocks, 2x4s, logs).  The master plan is to lay down tile in one area and Douglas Fir in the remaining areas. 

I’m wondering if it’s worth it to get some type of vapor barrier down against the soil.  The problem is all the crap that was left under the porch and the fact that there’s only a 2 foot by 2 foot access into the crawl space.  Is it crazy to consider cutting out a part of the floor to get that stuff out, lay down some sand as a cushion, then poly, followed by a thin layer of concrete?  That’s my cadillac approach but was wondering if it is over the top. 

The other problem is existing floor thickness- it’s nearly 2 inches of wood (including the ply and the underlying decking).  I want to use real wood flooring but don’t want to raise the floor another 3/4 of an inch because the door leading to the outside is already close to rubbing on the floor.  I’m thinking I could remove the plywood, but it may extend under the bottom plates of the exterior walls, right?  And, if I go that far, should I plan on reframing the floor in the short direction with 2×6 or 2×8?  I’m finding it hard to know where to draw the line I guess.

I’d appreciate any thoughts- good or bad.  As always, thanks for the help.