The term “ply,” as it refers to plywood, means the layers manufacturers use to create the boards at various thicknesses. Some projects won’t need a thick board, while others will. Ply achieves the right depth and can also make the boards stronger.
Each layer is known as a wood veneer. A veneer is a thin piece of wood that you can glue together to create a different number of plies. Plywood, then, is the finished product when the manufacturer glues the veneers together.
It’s important to note, though, that veneers can also have various thicknesses. Depending on your location, some parts of the home must meet specific standards for the number of plies required for a board of a certain depth, especially with external walls and roofing.
B. Types of Plywood
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.
5. Lumber Core
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.
Marine plywood is known as the strongest and most durable plywood.
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 plywoods are usually glued with veneers and it gives somewhat finished appearance.
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.
Sheathing plywood is made for framing and building structures because of its strength.
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.
C. Other Types of Boards Often Used as Plywood
There are some other types of wood board that people use in place of plywood. Although they aren’t technically classified as plywood, you can use them in many similar instances.
Some of the following alternatives can provide inexpensive options for those on a budget, while others can create a completely different finished look for your project.
1. Composite Woods
Composite woods is similar to traditional plywood in terms of sizes but have regular wood layers on the side and have external layers consist of fiberboard covered with a layer of hardwood.
Composite woods come in similar sizes as traditional plywood, but manufacturers don’t make them quite the same. They do use layers, but composites have regular wood layers on the inside and external layers that consist of fiberboard covered with a layer of hardwood.
The construction leaves the outside smooth and easy to work with, while the strong core gives the wood a durable and unyielding frame. You’ll find composite wood mostly on furniture and cabinetry.
Blockboard with strong screw holding ability and high bending strength.
Blockboard uses a similar construction as plywood, usually with three layers. The inner core has thick, square cuts of wood that are glued together to create the strong core. The outer layers are thin and enclose the wood, forming a thick piece of wood.
Sometimes, you’ll see finished outer layers for cabinetry and other furniture pieces on blockboard. While plywood is a good option for surfaces that need a strong surface, blockboard is more about the core and a decorative finish. Blockboards usually range in thickness from 3/8-inches to 1 3/16-inches.
Foamboard has a rot-resistant feature and the best alternative to plywood.
Foamboard has become more popular in recent years, offering a rot-resistant alternative to plywood. These boards have a reinforced polyurethane foam construction that is reinforced with fiberglass, creating a board that’s just as strong as plywood, but also offers extra protection against mildew, mold, and rotting.
Foamboard can also be significantly lighter in weight than plywood, even in the densest boards.
Medium density fiberboard great for jigs and fixtures.
The most common type of fiberboard is medium-density fiberboard, also known as MDF. This alternative to plywood consists of engineered wood fibers glued together to create a dense composite. You can find either hardwood or softwood MDF, or a combination of the two.
The benefit of this type of wood is that the small fibers create a finished piece without knots or rings. Unfortunately, you also won’t see the wood grain, which can be a drawback for people who want that authentic wood look for their furniture or other finished product.
MDF is a less expensive alternative to plywood, but is stronger than the least costly options, like particle board. Still, you might end up with cracks or split wood as you work because MDF won’t be able to handle a lot of stress.
The finished product is easy to cut and paint. Additionally, you don’t have to worry about splinters as you work because MDF’s dense construction results in a smooth finish.
Hardboard with medium density untempered hardboard.
Hardboard is a thin piece of fiberboard that often has one side rough and the other finished. Manufacturers use wood pieces to create hardboard, which then gets densely compressed to make a panel that doesn’t bend or warp.
Hardboard is exceptionally durable, despite its thin frame. It’s common to see this type of panel on kitchen countertops, furniture frames, and subflooring. Some people use hardboard for the base of their laminate flooring because it’s so strong and can stand up to constant wear and tear.
Particle board with excellent screw pull and strong internal bond for high adhesive performance.
Particleboard is one of the least expensive alternatives to plywood. Particleboard has no layered construction. Instead, it’s comprised of small slivers of wood scraps glued together to create a board. This is the type of material you usually find on inexpensive furniture pieces.
Particleboard may be cheaper than plywood, but it’s also much less durable. This type of wood can split and crack easily, and it’s not uncommon to hear about pieces breaking during assembly of particleboard products. You’ll also notice that particleboard is much heavier than plywood, making assembled pieces more difficult to transport.
One of the biggest issues with particleboard is that, in its regular form, it’s untreated, so it’s susceptible to swelling if it’s in an area with high moisture. If you’re going to use particleboard, you should ensure that you seal it correctly to avoid warping and swelling.
7. Moisture-resistant Particleboard
Moisture-resistant particle board keeps the board from swelling and warping in wet areas.
Moisture-resistant particleboard has the same construction as regular particleboard, except that manufacturers use a particular moisture-resistant resin to keep the board from swelling and warping in wet areas.
You’ll be able to tell the difference between regular particleboard and its moisture-resistant version by the color of the board. Moisture-resistant boards usually have a green dye added to the resin to make them distinguishable.