The best decking material that i can think of for a trailer would be pressure treated 2x6 or 2x8. It doesn't need any care and will likely last 20 years or more out there in the elements. What you wanna do is look at the endgrain and put the crown facing up. That way the boards don't cup and hold water. Use a sixteen penny nail as a spacer between your decking boards as you are laying them. That little bit of space between the boards allows them to shrink or swell without causing any problems.

If you had a small 4x8 trailer ... a 4x8 sheet of pressure treated plywood would be just right. You could probably get by with 1/2" but 5/8" or 3/4" thick would be better.




Another thing that's gaining popularity these days is what's called composite decking & boarding. It's made out of recycled plastic and sawdust. That's being used on a lot of high end jobs now because it's maintenance free and lasts indefinitely. It doesn't swell or shrink so that's a plus. It is kind of expensive to buy though.