noela wrote:
I am getting set to build an outdoor train layout. One part of the
layout will be roughly 4'X32' and be built like a deck, flat and
level. It will be supported on 24" centers. I am planning on using
3/4" sheets of plywood, and this is where I have my question. I am
thinking about using Pressure Treated 3/4" plywood sheets, my
reasoning is this: it will be subject to moisture, and maintaining
it, after I have installed the track over it will be a chore. I am
looking at a life time of 10-15 years before replacement. After
reading this thread, I am not sure if I am making the correct choice.
I have selected plywood as it will allow me to maintain a flat and
level surface, rather than use structural wood. I would really
appreciate any input from this group, even though it sounds as if this
topic doesn't belong here.
Thank you.

Buy regular CDX. The "X" is for exterior glue. Save the money.