Are Plywood Sheets Waterproof?

​Plywood sheets are not automatically waterproof. Standard plywood is made from real wood veneers, so it can absorb water, swell, and gradually lose strength if it stays wet. This article explains what waterproof means in real projects, which plywood types handle moisture best, what failures look like when the wrong panel is used, and how to select plywood that matches outdoor, bathroom, kitchen, formwork, or marine-adjacent needs.