Waterproof Adhesives Key to Marine Grade Plywood

Posted on 1/6/2021 11:09:11 AM By The Spruce

Marine-grade plywood might by it’s name imply that the laminated plies are waterproof. However, the plies used for marine plywood are neither waterproof, nor are they pressure treated like other lumber and grades of plywood so as to be resistant to rot. 

Instead, it’s the waterproof adhesives used in the bonding of the plies, that provide sufficient protection against exposure to moisture, boiling temperatures and high humidity to prevent the plywood absorbing water, and to stop the plies from delaminating and starting to fall apart.

While using specific types of wood and the number of plies used in a panel are not as important in non marine-grade plywood, the hardwood plywood in the five marine grades, and particularly when it’s used in the production of boat parts (and the boats, themselves) are more definitive for safety reasons. So is the number of plies used in the plywood panel and the choice of waterproof adhesives used to provide the protective finish. Hardwoods which combine light weight, a finer grain, and more strength are often chosen, and all wood is carefully inspected for defects and knotholes in any of the plies which could reduce the effectiveness of the waterproof adhesive’s bonding and protective finish.