Originally Posted by SloopJonB
For interior partitions, I never pay the price for marine ply - use good quality exterior ply and seal the edges with epoxy.
What I saw for a big difference between marine grade ply & exterior was on the exterior there seems to be more voids in between the layers. The exterior ply I got didn't come from a home depot type of store either.
I was snapping after picking up the first sheet of 1/2" marine ply at $85.00 a pop so the next sheet of ply I got was exterior. First cut I was amazed at the voids, thought it was a fluke. Made a couple of more cuts & what was left of the sheet & the pieces got recycled into a staging platform for working on the boat.
The other thing w/ exterior grade ply, it is meant to be covered with something, siding, roofing. The stuff I recycled into the platform is beginning to delaminate but I didn't seal the edges either.
That was my experience with exterior grade ply anyway.