There are many kinds of plywood, each of which is perfect for the task you want to use it for. Let's look at all the different ways plywood is made, so you can find exactly the type you need.
Plywood is made of layers of thin wood glued together with water resistant glues perfected in the 1930's when the animal was replaced by synthetic resins cured by microwaves. When you buy plywood, you must know what type of plywood you need, what kind of exposure the plywood will be exposed to. Exposure 1 can handle very limited exposure to water, while exposure 2 is suitable for dry locations.
Choose plywood by how many plies you need. Home construction plywood has three, five, seven or nine plies. Three ply is used for most built in and molded furniture. Five-ply is the most common plywood and usually used for subflooring, finish-flooring and sheathing. Seven and nine ply are used by hobbyists for woodworking.
Plywood has a two-letter rating of quality by side. One tells you the grade of the face side and the other letter, the backside.
- A-grade means a face free of knots
- B- and C-grades have limited blemishes
- D-grade can have open holes.
- A-C plywood has one excellent side and and one side that could have some blemishes.
- B-C plywood is considered furniture grade and has patches that look like footballs on the surfaces.
- A-B plywood is considered a specialty grade.
- C-D-X plywood is made for exterior use - that's what the X means. The D side may have patches and show some cracks and may have open knot holes.
- T and G plywood is a tongue on one side and groove on the other. This plywood interlocks to spread loads across joints on decks and floors.
Plywood is sold usually as a 4-foot x 8-foot sheet in six thicknesses; 5/16-inch, 3/8-inch, 7/16-inch, 1/2-inch, 5/8-inch. You can get 4-by-10 foot sheets for walls, as well, and 1 1/8-inch thickness for heavy duty floors. 3/8-inch plywood or 5/8-inch plywood is the most commonly used plywood and what you will use most unless you are doing some special project.
Use polyurethane glues to fasten plywood to other materials. Polyurethane glues resist the moisture that can destroy the joint. Use construction adhesives for gluing and screwing plywood to joists to avoid squeaks in floors and stairs. To cut plywood support the wood on saw horses. Use a circular saw set to a depth that will just cut through the plywood and cut with the best side down, so the veneer will not be damaged.
Plywood is a multi-use building material. Choosing and buying the plywood you need is easy. Using the best plywood for your project will make for the best job you can get.