Solid wood is wonderful to work with, but there are times when it isn’t the best choice, whether because of cost, design details or simply preference. Composite materials, such as plywood, can often be a better option.
Plywood is made by layering thin veneers of wood together with the grain of each veneer at 90 degrees to the layer above and below. The result is a dimensionally stable sheet. The type of adhesive and the quality of the veneer are what determine the grade of the sheet.
Ply (often referred to as sheet goods) and other composite materials have some advantages over solid wood. Depending on the product, it can be resistant to rot, weatherproof, or dimensionally stable.
This means that ply can actually be an unusually beautiful material to work with.
On the other end of the spectrum is
construction grade ply that is full of knots and voids. It is used
mostly for adding rigidity to a frame or floor, etc.
Sheet goods are graded either interior or exterior. The type of adhesive determines whether it will stand up to moisture or not. Don't try and use interior ply outside, the ply's will separate. If you want something that will stand up to the worst types of weather, marine plywood is your best choice.
Marine ply is made of high quality materials bonded with a waterproof adhesive. Used in boat building it truly will stand up to the elements.
If you are working on an outdoor project there are other types of manufactured wood replacements used for decking and other outdoor uses. These are made of various resins and have little or no real wood in them. Because they are manufactured the resins can be made specifically to resist rot. These composites often replace pressure treated wood. They are relatively new to the market, but are increasingly common.
Pressure treated wood is lumber that has been impregnated with chemicals that make the wood rot resistant. The wood is heavy and will last for years; however, exposure to the chemicals is dangerous. It’s best to use gloves and wear a mask if handling pressure treated wood.
Although pressure treated wood is becoming less toxic, people are switching to the resin wood replacements as a safer alternative. However, it’s still a good idea to use a mask if cutting any of the composite materials, because of the chemicals in the glues.
Other composite wood products include sheet goods such as particleboard, waferboard, and MDF (medium density fiberboard). These are all made of compressed wood particles of different sizes adhered together with various glues. These are all made of compressed wood particles of different sizes adhered together with various glues.