Teardrops n Tiny Travel Trailers

Use two part epoxy and thin it 10-15% with acetone to penetrate the wood. Apply to both sides of sheet with a roller and don't forget to roll all edges (including window cut-outs) with at least two coats/three on the cutouts. You can then sand lightly and apply epoxy paint. Must maintain at least 70 degrees to get it to set up. The hotter the faster.

I've built boats and RVs this way. It's the only thing that keeps moisture and rot out for years and years.

I prefer EverCoat brand epoxy.

Prem