Advantech OSB will outlast conventional plywood by a mile in the rain. I exposed it, flat (the worst way possible) as subfloor, to rains for 1+ year while building my house with only maybe 1mm of fiber degrading on the surface a few places. Many modern OSBs use hydrophobic glues impermeable to water.
OSB is not very nice either. Plywood is definitely the choice here.
I think MDF will easily last until his kids don't fit in it though. I don't think he's going to use it in the rain.
Advantech OSB will outlast conventional plywood by a mile in the rain. I exposed it, flat (the worst way possible) as subfloor, to rains for 1+ year while building my house with only maybe 1mm of fiber degrading on the surface a few places. Many modern OSBs use hydrophobic glues impermeable to water.
Maybe but it's basically made of splinters. Not something you want in a thing you have to touch!
That's what I was thinking. Plywood is a horrible choice.
Marine ply would be my choice
If it were going to be exposed to the elements, I would pick a pine and waterseal it or a marine ply and waterseal it.
It would fail eventually anyway, but either of those two options, depending on price, would be good and cheap enough to last.