Plywood is a simple, but effective material. This is used a lot in the world of construction due to its strong structure, but light weight. It’s quite a flexible material, not physically but in the sense that you can add many layers and make it as thick as you need.
Modern plywood as we know it was invented in the 1800’s. The famous two seater aircraft of World War Two, De Haviland Mosquito was mainly made of different grades of plywood. Furniture makers and Architects started using this material around the 20th century after the second world war when production of plywood became a bit more commercial, and also due to its economic value.
Plywood’s strength comes from the way in which it is made.
It is made up of different layers of veneer, with the inner layer being called the core, and the outer layers being called the faces. The number of layers included is always odd so that the faces look the same. This is good for objects which you’d see both sides of, like a door as it gives the illusion of it being one solid piece of wood rather than lots of layers stuck together.
Each layer is turned at a 90 degree angle from the last, this strengthens the structure of the product because the grains are going in different directions. It is then put together using glue. The type of glue depends on where the plywood will be used:
- Interior – this type of plywood could be glued using either highly resistant glue which is fairly resistant to moisture in the air, or intermediate glue which is resistant to mould, bacteria and moisture. Neither should be used for exterior plywood though.
- Exterior – This plywood is made using waterproof glue.
The plywood is then placed between two large hydraulic shelves and squeezed together whilst being heated to dry the glue, it can then be trimmed and sanded to give a better finish. The outer layers can be made of more expensive layers of wood to make it look better as they are usually thinner.
The more layers of veneer you have in the plywood, the stronger the structure will be and the more resistant to impact it will be, so that it won’t split, chip, crack all the way through or crumble. These layers also make it more resistant to shrinking, warping, twisting or swelling so much as ordinary wood.
You can get exact sizes and thickness’s when you buy plywood, which is handy if you’re on a budget, you’d only be paying for exactly how much you’d be using rather than having any waste.If you do buy plywood, be sure to look out for the initials APA (American Plywood Association), or DFPA (Douglas Fir Plywood Association) as these two companies represent most of the plywood manufacturers and test all plywood to ensure that the quality is to a high standard.
Written by Jade Turney – Building Tectonics.