Could use some guidance with wrapping PMF underneath

[yuppers]

Hey guys. I’m building a foamie trailer and I’m at the point where I need to figure out the details regarding the sidewall and floor PMF interface. I know you’re supposed to wrap it underneath and overlap by about 4 inches but I don’t know if I should seal the plywood first and then wrap the PMF or wrap the PMF and then seal the plywood.

[yuppers]

I was also wondering if could just PMF the bottom of my trailer too as I feel that could solve all my problems but I want to double check before I commit.

[GPW]

Yuppers ,Previously we wrapped the PMF under the edge , which in our humidity( morning dew) quickly rotted out ... Since then , we use a "drip edge" to channel all the water down and away from the underneath ...preventing any future rot or problems . . Something like this ...
If using a plywood floor best seal the ply THOROUGHLY with something like "the Mix"' ...

[tomhawk]

I did a variation on GPWs scheme. I did not like the idea of stooping down to glue flaps of canvas under the floor of the cabin; I am too old for that. Instead, I flipped the floor over and glued an 8" wide band of canvas around the bottom edge of the floor. Since the surface was facing up I could easily see what I was doing and did not have to glue anything upside down.

Then, when installing the walls, I wrapped the free edge of the canvas band onto the bottom of the wall and glued it. The bottom flap of canvas covering the wall was glued onto the wrapped canvas to provide a strong bond. I have towed my trailer many hours at 70 MPH. These walls are attached.

For illustration of this process see:
viewtopic.php?f=55&t=75248&p=1296691#p1296691

Tom

[ghcoe]

I lap the canvas 2" under the floor and glue it to the wood directly. Once it is dry, I paint the bottom of the floor with paint. I usually just roll the body onto it's side for this process to make it easy.

When I get the body onto the trailer, I add a drip edge using drywall end bead. I simply just screw it onto the bottom with pan screws. I start the screws, but leave a bit of a gap between the floor and the beading. then I add some Dap caulk between the floor and beading and then finish tightening the screw down. Clean up what caulk squishes out on the front and back. Then paint the same color as the body.