I've been thinking about the bottom layer of the floor. Thinking of but not committed to a foam sandwich floor. People have had success with that as well as a single sheet of say 3/4" plywood. There is probably no single right answer though many wrong ones.
Anyway, over the course of the evening I've considered the green treated plywood, marine grade plywood (which appears to only come in 3/4" at Lowe's), and even Hardiebacker.
If I go with the 3/4" marine grade I probably won't need to make a sandwich unless it is for insulation.
I don't know if treated lumber is safe in this situation, sure in an open air deck, but what about in a camper? Would arsenic seaping up be a danger? That said even the marine grade needs to be sealed according to Lowe's so if I seal the boards that could eliminate the risk.
Finally the Hardiebacker, it is certainly heavy at 39 pounds per 3'x5' sheet (0.42" thick) but that is not too much more than the weight per square foot as 3/4" plywood and would be very water resistant. Would it be brittle though when a piece of gravel is kicked up?
I'm planning to use Foamular on the walls and roof with 1/4" ply on the outside and 1/8" ply on the inside and have guesstimated that would come to about 350 lbs.
Any thoughts on the subject?
thanks,