Replacing wooden trailer floor with another one, which wood?

Buffalo board (phenolic ply) will be OK. 18mm usually suggested, no harm in goign up to 25mm if weight allows. If you have a bit of weight in hand, keruang, which is what they make HGV flooring from, is tough stuff.

But remember, all flooring will rot and weaken in time. Ali is actually a problem if not isolated where it joins steel.
 
We had ours done in wisa wire board which is an outdoor weather proof ply with wire mesh in it. It's designed for horseboxes and transport flooring and I liked the idea of the wire mesh rather than just boards
 
Keruing timber flooring, lay the 1st underlayer bolted to the chassis running longway, lay the top layer shortway ,wants a little champher on to create a v groove to give better grip ,will last you 10 years.
 
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