I used T&G 2"X 6" treated on 1 truck.
On the other I used none treated wood.
Used the counter sunk screws, All the wood is tung & Groove.
You can put drain oil on it to keep it from rotting.
There is a new plastic board 2X6 T&G on the market but it cost's a lot.
A 20' is just a litle over $100.00 It's called Rumber, It's 1 1/2" X 7" made from recycled tires & plastic & has a 20 year warranty.
comes in 6' 7' 16' 20' 24'
It would be good for horse traylers etc.
Should last a long time!! $$$$$$$$$$$$$$$$$$$
