What Is Plywood?
Plywood is cheap to use, strong and flexible, and good for building furniture and cabinetry, and many other undertakings. Plywood is made of very thin layers of wood called plies or veneers glued together.
Everyone has heard of plywood, and we assume it is some sort of “pressed wood” but beyond that we just really don’t know. Moreover, perhaps we “really don’ t care” until we need to use it in some building project, and then we need to understand it’s use’s and features and differences.
Plywood is cheap to use, strong and flexible, and good for building furniture and cabinetry, and many other undertakings. Plywood is made of very thin layers of wood called plies or veneers glued together. The middle core is usually veneer or manufactured wood. The outer plies called face and back are usually quality wood to be better in appearance. The face is better than the back.
Plywood is made by rotary cutting a log to produce plies. Steaming or boiling softens the log. It is then placed on a large lathe using very sharp blades, and cut into long strips of veneer. The strip is trimmed and cut into specific lengths, then oven dried.
This is made of an odd or sometimes even number of plies, up to nine plies are common. This is the strongest type of plywood and can be purchased in thickness of up to 1- 1/8 in. The grain is laid and bonded running at right angles to adjacent plies causing the grain to lock reducing shrinkage in width. It gives strength in all directions. The panel does have an overall grain running lengthwise. This grain direction provides the panel with its greatest strength. When installing the grain should be run horizontal to the joists or studs.
Lumber Core Plywood
Lumber core plywood is made in much the same way as Veneer-core with exception of the core. The core is a strip of solid lumber with thickness of up to 1 inch. The edges of lumber core plywood will hold screws fast. Plywood is either construction or hardwood. Construction is mainly softwood and is available in 4x8 panels. The most usual thickness is ¼ to ¾ in. Hardwood is used for decorative purposes and comes in panels of 4x7x8 or 4x10 and is 1/8 to ¾ in. thick.
Span rating means the maximum space in inches needed between supports to (efficiently) support a panel. This (span) is the rating in which it performs. Sheathing panels have two ratings roof and floor.
The American Plywood Association (APA) regulates the standard of plywood, and all home centers and lumberyards must meet these standards. Thicker panels and higher grade can be ordered but are more expensive.