I'm working on assembling a shed kit with a metal frame that requires an exterior plywood floor. The instructions specify I must use at least 5/8" thick plywood, but they strictly prohibit pressure-treated wood as it voids the warranty. Can anyone suggest what type of plywood is suitable for outdoor use and can handle moisture without being pressure treated?
3 Answers
Go for exterior sheathing plywood like CDX. It’s fine for exterior use since the glue holds strong against moisture. If it dries out after getting wet, you won’t have issues with delamination. Just ensure the long dimension connects perpendicularly to your floor joists for stability.
Marine grade plywood is your best bet for durability against moisture. It's specifically designed for wet environments, so it'll hold up well without needing pressure treatment.
Look for plywood with waterproof glue and minimal voids. Keeping it protected from moisture is key. I recommend applying a couple of coats of epoxy followed by some quality paint to seal it well.