Hi Lipets; Aluminum clad plywood is known also as "Sign Board". It is used for outdoor signs, it has thin aluminum skin bonded to each side. The skins sandwich the plywood core in between, making them exceptionally stiff since the aluminum skin cannot strech. The flex, versus the standard plywood is greatly minimized. It is glued with same grade glue as marine ply because is ment to withstand outdoor conditons for many years. Test it and you will be amazed. As a matter of fact, we just purchased new to us 1973 Argosy 26' which we gutted out. We are half way into building a new Stainless Steel undercarriage. We are also replacing entire floor, and two guesses what I have for it? 5/8 sign board. Wet floor wil be a thing of the past. Aluminum clad over it will keep all moisture out of the floor on both sides. If you need any further info I can give you manufacturers name. Good luck with the project. "boatdoc" P.S. we use it for floors in aluminum boats for years.