Teardrops n Tiny Travel Trailers

kevindford wrote:... bolting the floor, a sheet of 5/16 plywood, directly to the trailer frame, installing insulation within the C-beams of the trailer frame, then using corrugated plastic to seal the bottom of the frame....

• I wouldn't use the corrugated plastic on the bottom, because water will eventually find a way into the open spaces, and rot the underside of your plywood. I think a better way to have a waterproof material bonded under the plywood would be to use FRP (fiberglass reinforced panel) there, bonded with either Loctite PL Premium adhesive (505 is recommended, but most versions should work), or the Liquid Nails product made specifically for FRP ($24 a gallon, if you can find it). Once the FRP is bonded to the plywood (with the edges, in particular, being glued with a continuous bead), then there'll be no place for the water to enter from underneath, after you seal the bolts thru the floor to the frame.
• I would've done mine this way, if I hadn't used spray-can undercoating, which I can easily maintain and touch-up, if needed. I would also use the same adhesive to seal the edge grain of the plywood sheet. I did, then painted over it, as my floor sits exposed on top of the frame. No problems, yet!