The various types of plywood you’ll find in the hardware store can make your shopping trip seem overwhelming but understanding how they differ is the key to deciphering what the best kind is for your project.
Softwood is a type of plywood that manufacturers make using softwoods, like pine, redwood, or cedar. Although the name implies that these woods aren’t as strong as others, you might be surprised to know that construction workers typically use softwoods for exterior frame sheathing, roof sheathing, and sub-flooring.
Softwood plywood can also create things like sheds, temporary flooring, doghouses, shelving, and more.
Hardwood plywood typically has between three and seven layers and uses hardwoods, like birch, maple, oak, and walnut. Manufacturers glue the layers of wood at right angles to one another to create an incredibly strong finish.
Hardwoods are best for things like furniture, packing cases, sporting equipment, musical instruments, and other intricate projects that require strong frames.
Aircraft plywood is among the highest-grade, most durable kind you can find. This wood uses hardwoods, like mahogany or birch, to create an incredibly strong finished piece that can also resist heat and moisture.
The design incorporates some very thin veneers that can keep it light and flexible, while still giving it unyielding strength for the heftiest jobs. You’ll find this type of plywood in projects that need industrial-strength woods, like airplanes, boats, and furniture that’s meant to hold a lot of weight.
Exterior plywood has weather and water-resistant glue that holds each veneer together. When you create an exterior with plywood, one of the biggest – and most important – concerns is how the wood will handle wind, rain, and other weather. Exterior wood is meant to combat the elements to provide a strong, sturdy frame for years to come.
Exterior plywood sheets typically have several veneers glued together, classifying them as multi-ply. You can also choose various kinds of wood for exterior plywood, depending on the area in which you live. Some locations that experience unusually harsh seasons may fair better with wood like oak, which can resist mildew and mold from damp conditions.
Lumber core plywood is usually made with three plies, with two thin veneers on each side and a thick core. The outer veneers are typically made of a hardwood, while the inner core consists of strips of wood glued into one solid slab.
The inner core helps grasp screws, which makes it a good choice for projects that need a strong screw hold. One disadvantage is that poorly-made lumber core plywood may have voids within the core that diminish its strength and screw holding abilities.
You might think that the name of marine plywood, also known as marine-grade wood indicates that it’s waterproof, but that’s not the case. Instead, wood manufacturers make marine plywood with water-resistant exterior glue using the same layered construction as other woods.
The difference is in the grade of marine types. According to the APA – Engineered Wood Association, marine-grade wood consists of Western Larch or Douglas Fir woods and must have a B-grade or better, which we’ll discuss in the “More Details” section of this guide. This kind of wood is one of the best-constructed, high-graded plywood on the market.
Marine-grade wood isn’t resistant to mold, mildew, or rot from weather and water. Manufacturers don’t treat it with any chemicals, so rot and decay can be a problem unless you treat it with a pressure-preservative, as suggested by the APA.
To be graded as marine-grade, this wood must have no knotholes in any of its plies and use a top-performing water-resistant glue between plies. This ensures that the glue won’t stop working if the wood becomes damp from weather or wet conditions.
You’ll see marine-grade woods used mostly on outdoor furniture and decorative pieces, like gazebos, planter boxes, and benches.
7. Overlaid Plywood
Overlaid plywood, which can be either high or medium density (HDO or MDO), is a kind that utilizes the same structure of regular sheets with veneers glued to one another. However, overlaid sheets have an overlaid face that gives it a somewhat finished appearance.
The finished exterior isn’t necessarily for decoration, but instead gives the panels a durable surface that’s also smooth enough to keep water and other particles from damaging or sticking to it. The coating also helps the wood resist scratches and other abrasions that may happen during transport and construction.
Manufacturers bond the exterior surfaces to the rest of the veneers through a process of heat and pressure. High-density overlaid panels have more resin than medium-density panels, making them a bit more expensive. However, both can make a finished project stronger and more durable than can traditional plywood.
Structural plywood, also known as sheathing plywood, is not for looks, but rather, strength for framing and building structures in which you’ll eventually cover the wood. This type of wood needs a very strong adhesive to keep the plies together.
You can use structural woods on the inside or outside of a building, but they aren’t typically as weather-resistant as other types. Structural woods usually have a C or D grade, but no higher, so they’ll be an inexpensive option compared to some woods, but they also may not have the high performance you need for outdoor structures.