Why is plywood so strong?
There are several reasons plywood can rival regular wood in various arenas.
Here are three things that make plywood strong:
1.Layering
2.Alternate cross sheeting
3.Adhesives
Let’s explore these in more depth.
Plywood Strength Through Layering
Have you ever looked at those cable cars and wondered how such a small wire could hold such a large object?
Those small cables are strong because they are not one cable – they are many cables bound together.
Similarly, plywood achieves high strength through layering. By taking multiple small boards and securing them together, you get a board that is even stronger than normal.
Layering helps eliminate problems with knots. With regular solid wood, one knot can go all the way through the board – even if it’s a thick cut!
However, with plywood, you don’t need to worry as much about knots. Yes, they are still there; however, they don’t extend through the board.
Layering isn’t the only way plywood achieves extreme strength; plywood also achieves strength through laying in alternate directions.
Plywood Strength Through Cross Sheeting
Regular solid wood is strong; however, all the grain is running in the same direction. While this creates strength under some circumstances, it can create weakness in others.
For instance, regular wood is more prone to splitting. Why? With the wood fibers running in the same direction, a split can spread through the whole board.
With plywood, we can prevent a split through the multi-layered, alternating grain pattern. Like a tear-resistant fabric, where the weaves run in alternating directions, plywood prevents splits by alternating the grain’s directions.
This strength only increases with the layers of the plywood. A five-ply board will have greater strength than a three-ply board.
Plywood Strength Through Adhesives
Maybe you’ve read something like this on your bottle of wood glue: Dries Stronger than Wood!
Indeed, if you’ve ever tried to rip apart something that was properly wood glued, you’ll often find that the wood rips, but the glue remains intact.
Good plywood uses an adhesive that acts to increase the overall strength of the wood. Sometimes, you’ll find different grades of exposures listed with the plywood.
Exposure 1: moderately waterproof, will not stand up against water over extended periods.
Exposure 2: water-resistant but should not be exposed to torrential water.
Some of the adhesives used in plywood also have a waterproofing element. Marine-grade plywood is probably one of the strongest of all the plywoods. Though it’s expensive, it lasts a long time.
