Originally Posted by ermracing
Our original floor was plywood under the rubber mat, somewhere around 3/4" thick total. We used 1/2" foam board insulation with furring strips, 9/16(?) OSB and then some click laminate wood flooring. We still have the original floor in the workshop and it's only a slight (1/4") difference between the original and new sections.
I did something similar on our short bus and it worked decently but it had more headroom than our big bus does. Our big bus didn't have any wood.. just sheet metal and ~3/8" rubber. I figure with a good underlayment and some fan fold, we'd probably be around 1/2-5/8" which would fine for what we are doing.