In today’s day and age, it’s easy to go through life without an inkling of how products are made, sourced or manufactured. Just think about supermarkets: how often do you find yourself pondering about the supply chains that got the goods from A to B? Well, the same is true of DIY, particularly sheet materials like plywood. Despite its status as one of the most ubiquitous multi-purpose building materials out there, many people couldn’t tell you how it is produced.
This is exactly why we’re here – to answer the big old question: how is plywood manufactured and what is it made of? You might find that the process is more sophisticated than you gave it credit for…
What is plywood exactly?
Before we get to the juicy bit of this article, let’s make sure everyone is on the same page. What makes plywood plywood?
Well, for a start, it’s a form of engineered wood. Made up of thin layers of wood veneers that give the material its name, it’s wonderfully robust and can take a lot of weight. Here’s another fun fact: these bonded layers, also known as “plies”, come from the French verb plier (to fold). If you think about it, ply is basically sheets of wood – either hardwood or softwood – folded together.
And this is done via a sophisticated cross-graining technique that guarantees a powerful degree of stability and strength thanks to how each layer is rotated and pressed together. Speaking of, it’s time to dig deeper into the process.
How is plywood made?
At its very simplest the plywood manufacturing process looks like this. Plywood panels are created by peeling logged hardwood or, most commonly, softwood into large sheets. These veneers are then dried and pressure-treated at extremely high temperatures, before being lathered up in glue and bound together using these powerful adhesives.
After all this has happened, the sheets should start looking like plywood. Then it’s simply a matter of trimming the ply to size, sanding down any imperfections and finishing them off. Throughout the process, state-of-the-art machinery will conduct quality control checks using lasers to see that everything is running smoothly.
A walkthrough of the manufacturing process in 9 steps
The journey of plywood from raw timber to a finished product ready for shipment is a highly specialised process. We’ve touched on the basics, but here’s a more comprehensive look at how plywood in manufactured.
1. Lumbering the timber
The first step in plywood production begins with the selection and felling of suitable trees, ideally from FSC-certified sources. The wood used for plywood is largely taken from softwood species, although hardwoods can also be used for specific types of plywood that require a bit of extra hardiness. Common softwoods used include pine, spruce, fir and cedar. Softwood species are typically preferred by manufacturers thanks to their straight grain, ease of peeling, and abundance, thus, cost-effectiveness. These trees also tend to have fewer knots, making the ply produced more uniform in texture.
On the flip side, the hardwoods commonly used include birch, oak, and maple, especially for decorative plywood or products that need enhanced strength and durability. Hardwood ply tends to be denser and stronger, with finer grain patterns, making it ideal for furniture-making and high-end interior applications.
2. Log sorting and preparation
After debarking, the logs are sorted into categories based on their size, species and quality. This helps determine which logs will be used for specific plywood products. The logs are then conditioned by soaking in hot water or steaming, which softens the wood, making it easier to peel into thin veneers.
3. Peeling the logs into veneers
The next step looks like this: the logs are placed into a lathe, a machine designed to rotate them at high speeds while a sharp blade peels them into long, continuous sheets of veneer. These sheets typically range from 1mm to 4mm thick, depending on the desired final product. Once created, the veneer sheets are wound onto large spools, where they are then carefully inspected for defects.
4. Drying the veneers
After the peeling stage, the veneers are dried to reduce their moisture content. This is done by either air-drying them or via large industrial dryers that expose the wood to intensely hot air, ensuring that they are dry enough for glueing further down the line. This step is crucial to prevent warping or splitting later in the process, which can ruin the shape and structural integrity of the product.
5. Grading and sorting the veneers
After drying, the veneers are sorted and graded based on their quality. Veneers are examined for knots, cracks, grain patterns and any other possible defects. High-quality veneers are kept for the outer layers of the plywood, while lower-grade veneers are used for the inner layers.
6. Applying adhesive
Once sorted, each veneer sheet is coated with a strong adhesive or glue, typically a phenol-formaldehyde resin. This glue is applied to both sides of the veneers to achieve a nice solid bond during the pressing process. The amount of adhesive used depends on the intended grade and durability of the final plywood product.
7. Pressing the layers together
The veneers, now coated with adhesive, are stacked together in alternating grain directions (a technique called cross-graining). These stacks are then placed into a hot press, where heat and pressure are applied to bond the layers to give the plywood its renowned strength and dimensional stability. As you might’ve guessed, the number of layers varies based on the thickness required.
8. Trimming and sanding
Once the plywood has been pressed and bonded, the large sheets are removed from the press and allowed to cool. The edges are then trimmed to the required size and the plywood is cut to specific dimensions based on customer requirements.
If you’re interested in how different plywood thicknesses can impact your project, be sure to check out our guide on plywood thickness for the full scoop.
After all the trimming, the plywood is sanded down to achieve a smooth, even surface, and any excess glue that may have seeped out during the pressing process is removed.
9. Quality control and packaging
After the plywood is fully processed, it undergoes a series of quality control checks done by both people and machines with lasers that can detect any imperfections. This includes visual inspection for any defects or inconsistencies, as well as testing for moisture content, strength and other characteristics.
If the plywood passes the inspection, it should be ready to be packaged for shipment. Here, plywood is usually wrapped in plastic to protect it from external moisture and damage during transport.
Et voila! The plywood is ready for distribution to builders, furniture makers and DIY enthusiasts.
The key properties of plywood
As we’ve established, plywood is celebrated for its versatility. Part and parcel of this is its construction-attuned characteristics such as its flexibility, strength, moisture resistance, dimensional stability and insulating powers. The cherry on top is that it’s relatively inexpensive when compared to other building materials like solid construction timber.
All of the above properties are owing to the plywood’s layered construction; not only does the cross-graining enhance its strength but, along with strong adhesives keeping the plies together, weight can be distributed evenly across the surface without the risk of the material splitting. And don’t forget the tanalising stage – this type of pressure treatment keeps the ply sturdier and longer-lasting on the whole.
Its application and uses
Plywood has been used and manufactured on an industrial scale since the 1850s. You might be surprised to learn that in these earlier days, rather than the plywood board we tend to think of now, it was mostly found in moulded form for furniture. In fact, furniture design actually played a crucial role in driving innovation when it comes to its usage. Today, plywood’s application is far wider than furniture. In the construction industry, engineering, interior design and in general DIY, plywood makes its mark.
