Thickness by application
| Thickness | Typical marine use |
|---|---|
| 4–6 mm | Curved/bending panels, hull linings, ceilings, light fit-out |
| 9 mm | Cabinetry, lockers, light partitions, furniture |
| 12 mm | Bulkheads, general joinery, cabin soles (light craft) |
| 15–18 mm | Structural bulkheads, soles, decks, framing |
| 18–25 mm | Decks, transoms, stringers, load-bearing structure |
Bending vs structural
Thin panels (4–6 mm) take a curve without forcing and are right for hull skins formed over a frame and for linings. As the part carries load — bulkheads, soles, decks — step up the thickness for stiffness and screw-holding. For transoms that carry an outboard or hardware, go to the top of the range and consider doubling up.
Grade matters more than thickness
A thick board with a poor glue line will still delaminate. For any marine application, specify IS 710 BWP — a 100% phenolic-bonded board with a full hardwood core. See IS 710 vs IS 303 for why commercial grades don't belong below the waterline.
Finishing
Even marine ply lasts longer sealed. Epoxy-coat or seal cut edges and faces, especially on decks and transoms, to keep water out of the end grain. See our marine plywood grades and sizes.