Plywood is a construction material used across many industries. From crate builders and woodworkers, to the marine and aviation industries. Plywood is a strong, durable, cost effective, and in some cases beautiful material. Because of its broad use there are a variety of standards to which it can be made. For industrial users, the NIST Standard PS 1-09 (“Structural Plywood”) is very commonly referenced. What follows is based on that standard. Please reference the full standard for anything other than casual use.
Where is the plywood going to be used?
The first great divider of plywood types is the environment where the finished good is to be used. There are two broad types “Exposure 1” and “Exterior.” Exposure 1 plywood is used in areas where the plywood will not be exposed to weather permanently, but it may have some exposure during construction. Exterior on the other hand is designed to handle repeated wetting and drying cycles that would result from being left outdoors for an extended period of time.
What performance do you need?
The next big division is what quality of layers do you want to make up the plywood. The highest grades can be given a clear or stained finish. Lower grades may be painted, and the lowest grades have significant flaws. Higher grades have not only better appearance, but higher strength. Specialty grades exist for specific industries (construction, aerospace, marine) and have their own standards.
What different veneer types are there?
Plywood is specified based on location (Exposure 1 vs. Exterior) and veneer type. Typically this is done in the form X-Y Exterior or X-Y Exposure 1, where X and Y would be the veneer types on the two sides of the plywood sheets.
N Veneers are the highest quality veneers, selected only when you want a natural finish. This typically means a stain, polyurethane, or any other finish where the visible grain is an important part of the final appearance of the installed wood.
A Veneers are used when you want to be able to paint the surface with little or no preparation.
B Veneers are general purpose. They are used in high quality plywood and can be prepped for painting if necessary. A very good choice for many applications.
C Veneers are strong but have no emphasis placed on looks. They offer the consistent performance of B and higher veneers without the cost. Ideal for situations where no surface finish is applied. B-C Exterior plywood is a common choice for high-grade crates as it tolerates weather, has a good visual appearance, and has very high strength.
D Veneers are used where visual appearance and maximum strength is not important. Commonly used in construction, they may have significant aesthetic flaws but their strength is not meaningfully compromised. C-D Exterior plywood is a common choice for home construction.
Which plywood should I use?
The plywood types available from local suppliers will dictate all but the largest orders for plywood. The home construction industry dominates the plywood market. Select plywood sold through construction suppliers for the highest value. Specialty marine and aerospace plywood is also available readily, but from far fewer suppliers. For most crates, the materials typically available at home improvement stores are a great choice due to their immediate availability, high performance, and low cost.