Plywood is an artificially-made product made from wood and comes under the category of engineered wood. The manufacturing process of plywood consists of sticking three or more boards together to create a board of uniform thickness.
Plywood consists of layers of wood veneer bonded together with a resin to form boards that we use for various purposes like in construction and making furniture. There are several types of plywood that you can get, depending on the particular requirement of your project. Plywood is a cost-effective and eco-friendly alternative to natural wood.
We classify plywood into different types based on various parameters. It is important to understand the system by which the different types of plywood exist to identify the best category for a particular job. Given below are the various groupings:
- Classification of Plywood by Layers
- Classification of Plywood by Material
- Special Grades of Plywood
- Classification of Plywood by Grade
- Plywood Alternatives
Classification of Plywood by Layers
The plywood we use for walls, furniture, painted cabinets, and other various structures comes in varying layers. The number of layers that you can get in plywood may range between three to 13 layers.
It is the commonest form of plywood. For example, 3-ply plywood has three layers of wood veneer. This type of plywood has enough thickness to make the boards strong and durable. You will find this type of plywood widely used for indoor applications.
Here, you get five layers of wood veneer. Again, you will find 5-ply plywood used for projects that don’t need too high strength and durability levels, and we usually use this form of plywood for indoor rather than outdoor use.
When it comes to multi-ply plywood, the minimum number of layers is more than five, and you may see up to 13 layers of veneer in this type of plywood. As a result, you get an incredibly strong and durable frame for building a home with multi-ply plywood that will withstand a beating from the elements.
Classification of Plywood by Material
If you visit a hardware store, you will see various types of plywood and one category you will see is plywood classified according to the type of wood that makes it up. Here are the common varieties of plywood that you may come across:
Softwood plywood consists of different types of softwood like cedar, redwood, or pine. This type of plywood is surprisingly strong and plays a prominent role in sub-flooring, roof sheathing, exterior frame sheathing, sheds, shelving, and doghouses.
This type of plywood comes in three to seven layers of wood veneer. The manufacturers arrange the subsequent layers of veneer with the wood grain in opposite directions. The opposite grain direction makes the boards incredibly strong.
Hardwood plywood is usually made from hardwoods like birch, oak, maple, walnut, and poplar. We use this type of plywood for making packing cases, musical instruments, and furniture that needs strong frames.
This is the most durable and highest-grade of plywood that you can get. Aircraft plywood is typically made from birch or mahogany, and we treat it to make it resistant to moisture and heat.
Another notable feature of this type of plywood is that it consists of many layers of extremely thin wood veneers. As a result, the plywood is very light and highly flexible, which is what we need when building boats or aircraft parts.
As the name suggests, it is safe to use this type of plywood for outdoor applications (rather than using interior plywood).
The wood is treated with water-resistant and weather-proof glue that greatly increases its durability. It can withstand wind, rain, or any extreme weather conditions to a great extent.
Exterior plywood also consists of several layers of veneer glued together, putting it in the category of multi-ply. If you live in a place that experiences harsh weather, you will do well to use this type of plywood You can even use it indoors in places that experience high relative humidity, like in coastal areas.
See the main differences between indoor and outdoor plywood here.
Lumber Core Plywood
Lumber core plywood consists of three plies – a thick lumber core bounded by two thin veneer layers on either side. The outer veneers are usually made from hardwood, and the inner core may consist of a slab of wood strips glued together.
The inner core holds the real strength, which makes it easy to drive in screws firmly. However, with this type of plywood, you need to be careful about the quality of the core. If there is a void in the core, it could affect the ability to take screws.
We also call this type of marine-grade plywood, but contrary to what you may believe, it is not waterproof. Instead, manufacturers treat the surface of marine plywood with water-resistant glue, and the process of layering is similar to that of other types of plywood.
According to the Engineered Wood Association (APA), the distinguishing feature of marine-grade plywood is that it is made of softwood like Douglas fir or western larch. It has to be in the category of B-grade or better.
Marine-grade plywood doesn’t have any particular resistance to rot, mildew, or mold and isn’t weather resistant or water-resistant. In addition, it does not undergo any special chemical treatment, so if you use this type of plywood, you need to apply a pressure preservative.
We use marine plywood for outdoor furniture, decorative pieces, benches, planter boxes, and building gazebos.
Read more about Marine Plywood here.
Overlaid plywood comes in either medium density (MDO) or high density (HDO). Manufacturers make this type of plywood the same way as regular plywood by gluing wood veneer sheets together.
What makes overlaid plywood different is its overlaid face, giving it a better overall appearance. This overlaid surface isn’t necessarily for cosmetic purposes only, as it also improves the plywood’s resistance to water and abrasion.
The manufacturers bond the veneer layers with the exterior surface by applying heat and pressure. As a result, the resin content of high-density overlaid panels is more than that of medium-density panels. But both grades are significantly stronger and more durable.
Also called sheathing plywood, structural plywood is made for strength rather than looks. You will see this type of plywood used in framing structures that will eventually be covered with wood. The adhesive of structural plywood is exceptionally strong.
Although you can also use structural plywood outside a building, you will not find it as weather-resistant as many other varieties of plywood. In addition, structural plywood usually comes in C or D grade, but you won’t find it in a higher grade than that.
Other Types of Plywood
Some other categories of plywood that are not so common are still worth mentioning in our list here. There is some overlap in the terminology of these types of plywood. Don’t be surprised if you get plywood named as those in the list below, but they may resemble the types that we have already mentioned above.
Here are a few of the other types of plywood you may come across:
- Flexible plywood
- Tropical plywood
- Composite plywood
- Commercial plywood
- Sanded plywood
- Veneer core plywood
- MR grade plywood
- Decorative plywood
Special Grades of Plywood
Apart from the different grades of plywood, there are a few special grades of plywood that do not fall into a specific type. These grades of plywood are unique to their class and noted for their superior quality. Among the best two of this class are Baltic birch plywood and Luan plywood.
Baltic Birch Plywood
Baltic birch plywood comes from birch lumber which is native to the region of Europe in the area of the Baltic Sea. It consists of crossbanded layers of Baltic veneer, giving it tremendous strength.
This type of plywood was originally used to make cabinets, but today it plays a key role in various woodworking projects, from furniture and construction to kitchen counters and flooring.
Baltic birch plywood performs better in taking screws and nails than many forms of engineered wood like MDF.
We also call Lauan plywood “Luan” or “Philippine mahogany plywood.” Although its name contains the word “mahogany,” it consists of layers of hardwood veneers made from a variety of wood species but primarily from lumber of the Shorea tree.
Lauan plywood exhibits some excellent properties like having consistent color, density, and dimensional stability. It is easy to peel for use in underlayment for flooring. You will also find this material easy to bend and work with – the ideal plywood for a DIYer.
Classification of Plywood by Grade
There is a strict system of classifying plywood into different grades depending on the quality and requirements of the end-user. Knowing the different plywood grades will ensure that you get to be the best match for your woodworking projects.
The plywood grading system involves segregating plywood based on the quality of the wood, material used, and the number and thickness of the layers used. The letters A, B, C, and D designate the different grades, A being the best and D being the lowest in quality.
However, you will usually find two letters printed on the plywood. The first letter denotes the grade of the front and the second, the grade of the back – the face that typically (but not always) will not be visible.
For example, if you see “A-B” printed on the surface of the plywood, it means that the front has A-grade plywood, but the opposite face consists of B-grade plywood. You might also see “X” additionally printed like “A-CX.” It means that it is also exterior-grade plywood that you can use outdoors.
In what we could best describe as “plywood alternatives,” we have a few classes of engineered boards that we use in the place of plywood. These boards aren’t plywood in the conventional sense of the word, but they make a viable and cost-effective substitute. These boards can also impart a suitable finishing touch to your projects.
You will get composite woods in the same sizes as traditional plywood, but the manufacturing method differs. These boards have layers, but you may find regular wood layers on the inside, and the external layers may consist of fiberboard with a top layer of hardwood.
The result is that you can work easily on the smooth outer surface, but you also get a strong core, which offers adequate mechanical strength. We use composite wood to make furniture and cabinets.
The construction of blockboard is similar to that of three-layered plywood. It has an inner core consisting of square cuts of wood bound together with adhesive to form a robust core. The outer layer has a thin sheet of wood.
It is common to use blockboard for finishing the outer layers of cabinets and various furniture pieces. In addition, where you need a strong surface, you can use blockboard instead of plywood to get a stronger and more decorative finish.
Foamboard is a type of board that has gained popularity in recent years. It is a rot-resistant solution to traditional plywood. It consists of a layer of polyurethane foam sandwiched between two layers of thin wood.
Even the densest foamboards can be lighter than the lightest grades of plywood. The advantage of foamboard is that you get a light, durable and easy-to-assemble board, resistant to mildew, rot, and mold.
Fiberboard has many variations, but the commonest form is medium-density fiberboard (MDF). It is one of the most popular alternatives to plywood.
MDF comprises wood fibers that manufacturers bind together under heat and pressure to form solid, dense boards. You can get softwood and hardwood MDF or a mix of the two.
Fiberboard has the advantage of having a homogenous consistency with no knots, grain patterns, or whorls showing on the surface. But those who prefer the patterns of natural wood will not appreciate this material.
However, MDF is much cheaper than plywood, stronger, and laminated to have a glossy or wood-like finish. It also exhibits excellent acoustic properties, making it suitable for making speaker enclosures and using them in sound recording studios.
You can learn more about MDF and other composite woods in another of our posts.
The distinguishing feature of hardboard is that it is a thin piece of fiberboard with a rough side and a finished side. Hardboard comes from a process that involves wood pieces highly compressed together to create a panel that will not bend or warp.
You will see hardboard used on kitchen countertops, furniture frames, and subflooring. In addition, interior decorators use these boards for making laminated flooring because of their strength and resistance to wear and tear.
Particleboard is one of the most cost-effective alternatives to plywood. It does not consist of layers. But instead, it has small slivers of wood scraps bonded together to create a board. You will see inexpensive furniture made of this material.
Although particle board is much cheaper than plywood, it is also very low on durability. It splits and cracks easily, and it is heavier than plywood. Particleboard is also very prone to damage due to water and moisture, so it needs adequate sealing.
Recognizing the difficulties with regular particleboard, manufacturers came up with what we today call moisture-resistant particleboard. The construction process is the same as traditional particleboard, but the manufacturers add a waterproof resin to keep the board from getting damaged in moisture-prone areas.
You can tell the difference between regular particleboard and moisture-resistant particleboard by the color. Moisture-resistant particleboard has a greenish color attributed to the waterproof resin that it contains.
Plywood comes in many types, qualities, and sizes. It is a vast subject, and there is still so much to be discussed. But we have covered a lot of information in this post. We hope that we have given you a better insight into this versatile form of wood.
If you type “plywood” in the search bar of our website, you will find several more interesting posts on plywood. You can read those articles as well to gain an even better understanding of plywood. We hope that by reading this post you get the most suitable plywood for your woodworking projects.