Dont know if I am overthinking this, but I am looking for the best practices for how to coat the exterior wood floor of my first TTT build. I have tried searching, but have not found much on the topic.
Construction will be 1/2" sanded clear plywood with a 2x4 frame filled with 1.5" rigid foam insulation (pink sheets) with a 1/2" clear sanded plywood interior skin. The inner and outer skins will be glued and screwed to the 2x4 frame to give a torsion box construction for added rigidity.
Anywho, I am wondering about a couple of things. First, what is the best seam treatment on the underside? I will have two seams running across the width of the trailer as its 5'x9' floor. Cant do that with 4'x8' sheets and less than 2 seams. Second, what surface treatment (exterior) has been successful? I am considering the following but open to anything. I am leaning away from fiberglassing or a separate rigid skin (i.e. filon, aluminum, etc) but could be convinced if other "applied" solutions are all sub par.
Option 1: standard exterior house paint. Oil based and give it 3-4 coats. Would seal the seams and screw holes with paintable silicone caulking and.
Option 2: 3 coats of oil based poly thinned 50, 25, and 0% with MEK and then overcoat with two coats of Monstaliner. Not sure about the seams and screw holes in this case. Could use paintable caulk or bondo body filler.
Option 3: Behr (or other brand) of deck resurfacing paint. https://www.homedepot.com/p/BEHR-PREMIUM-ADVANCED-DECKOVER-1-gal-SC-102-Slate-Smooth-Solid-Color-Exterior-Wood-and-Concrete-Coating-500001/308486653 Would apply directly to the wood with a couple coats. I would assume bondo or paintable caulk for seams and screw holes.
Any other suggestions I would be greatly appreciative.