Plywood: A Buyer’s Guide

I am a sales associate at a retail establishment that sells plywood and other building materials. Every day I deal with customers who come in excited to get started on a new project, but don’t really know what sheet goods they need. With so many different products to choose from, I can understand their dilemma. It took me several weeks to learn them and all their applications. Often the customer will bring in a materials list from a magazine, but the problem with so many of these is that they usually list only one option, depriving the builder or craftsman the variety of choices out there. Sometimes the customer isn’t really building anything, but rather needs shelving for a garage, boarding up a window or repairing the deck of a boat. I have put together this guide in order to help with navigating through the myriad of choices available. It’s meant to be more of a buyer’s guide than an academic study of building materials.

The first question that I usually ask is whether the plywood is to be used in an interior or exterior application. That is, will the plywood be exposed to the elements or remain indoors. Let’s start with an exterior application. Many people believe that all exterior products are waterproof. This is not true. The only plywood that is waterproof is wolmanized plywood which has undergone a special pressure-treated process. If the customer needs an exterior product that requires no additional painting or sealing, this is the only choice. A common use for treated plywood is exterior flooring for trailers or boats. What makes an exterior product “exterior” is the glue that is used to bind its plies together. Plywood exposed to the elements for extended periods of time can delaminate (the plies separate) without the stronger glue being used. The least expensive of these exterior products are the pine sheeting grade plywoods, so called for their standard applications as sub-floor, roof and wall sheeting. These products can also be considered general purpose plywood suitable for such projects as boarding up windows, temporary ground cover and rough cabinetry. Because of its instability (doesn’t stay flat), it would not be recommended for shelving or any other project where warping would cause problems. Sheeting plywood comes knotty both sides (CDX) and sanded 1 side (BC). If a more finished, exterior product is needed, I would generally recommend a product called Arauco. This product has a better quality of pine as its top veneer and has a tighter core with fewer voids. It would be suitable for outdoor crafts and games such as corn-hole toss.

Another misconception is that marine grade plywood is treated or that it is the exclusive product used for all boat applications. Both are false. Marine grade plywood needs sealed, painted or wrapped in order to render it waterproof. The marine grade is a function of strength. It has virtually no voids in the core, making it extremely strong and less susceptible to water infiltration. It’s primary use is in the structure of watercraft, such as the hull or transom and is often wrapped in fiberglass or epoxy.

If the plywood is to be used in an interior application, I will usually ask if it will be painted or stained. If painted, I will recommend a tight grained veneer such as birch or poplar which are generally smoother. An open grained veneer such as oak is more difficult to paint without the grain showing through.

If the project is to be stained, the customer has a wide variety of species to choose from according to personal preference.

Lauan plywood is a good general purpose, interior product. Generally thought of as floor underlayment, lauan also comes in many other thicknesses and can be used as shelving, cabinetry and even interior wall sheeting.

I consider Baltic birch to be the highest quality of plywood on the market. It generally comes in 5′ x5′ sheets and has the tightest core. It’s very stable and paints easily. Baltic birch is ideal for craft work such as scrolling and pattern making and often used in cabinetry, especially drawer making.

In closing, I would like to address an important issue. So much of our plywood is actually built oversees (China) and the process used results in a less dry core than domestic built plywood. Consequently, this results in a less stable product. If stability is important to the buyer, I recommend plywood with a domestic core and getting it from a plywood dealer rather than a big home improvement warehouse.

I hope this guide proves helpful in giving the buyer the tools needed to make a more informed decision when buying plywood.