Under Coating

[Angus McBagpipe]

I've been working away and I need to start thinking about the day I mount by box to the steel frame.
The interior is already sealed up. I'd like now to "Undercoat" the box. The floor is comprised of OSB & Plywood some softwood spars.
What product should I be looking for to protect the underside from elements?

[Vtec44]

I would say something durable to repel soft impact and water. Maybe some sort of truck bed lining?

[noseoil]

I did 2 coats of urethane to seal things, then used 2 coats of Henry's white roof coat as the actual finish. Figured if it stands up to the sun in Arizona, it should be good underneath the floor. It's soft for rocks, water proof & easier to see if I have to crawl around looking at things. I really like it, rinses off at the car wash after a road trip & has lasted 20,000 plus miles.

[booyah]

So I used asphalt paint (Black Beauty fence post paint) to undercoat mine. Its fairly soft, and thick, and if its meant to protect fence posts in the ground I figured it would do well for a camper off the ground.
I also have insulation between that and the ground, so it doesnt really get impacts from road items, the insulation does.

(Insulation is held up with screws and fender washers, but I also put an extra coat of paint on before I stuck the insulation down, to act as an adhesive)