Fibergl coating of wood?

I use a sub-floor product that is OSB but withstands weather for an extended time. It's called Advantech and it comes in various thicknesses. I usually buy the 1 1/8" thickness. We had a sheet left on the job for 5 months and it wasn't damaged. If painted, I'm sure this product would last for many years. It could be cut to size and it is very dense and heavy. Particle board is not a good idea for exterior use. Good luck.