Depending on the project, exterior plywood sheets 9mm are ideal for general joinery and construction projects. This material has a hardwood face, and is suited for projects like sheds and floor decking, but you should apply a protective coating for added protection. You can also use them to build underfloor heating, flooring, and carpeting. They can be used to cover concrete frameworks, too. This product is often scarfed, or cut to two feet by four feet.