Gluing thin pieces of wood together to form a thicker one was used by ancient Egyptians, but plywood as we know it was born in the 20th century. A 4x8-foot sheet of plywood is typically made up of an uneven number of thin wood layers, or plies, glued together with their grain running at right angles to one another. This cross-banded construction gives plywood great strength in all directions. It also results in extra dimensional stability—plywood doesn't swell or crack like solid sawed lumber. Plywood also has another big advantage: It's available in panels wider than natural boards and in thicknesses ranging from 1/8 to 11/4 inches in 1/8-inch increments.
With so many types to choose from, picking the right plywood can feel like a daunting task. That's where we come in. We'll give you all the information you need to choose the perfect plywood for your built-in project.
Two types of softwood plywood are manufactured: interior, which is assembled with moisture-resistant glue; and exterior, which is made with 100 percent waterproof glue. All softwood plywood is sold by appearance grades using letter designations, with A being the highest quality. The two sides may carry different grades, such as A-C plywood. If you choose softwood, avoid boards with loose knots. Loose knots often fall out as the wood dries, leaving a hole. Tight knots are acceptable but need sealing.
Hardwood plywood differs from the softwood variety in that its face and back veneers are of a hardwood species such as red oak or maple. It is also assembled to best display grain and is strictly for interior use.
Grade stamps on plywood tell you the quality of face and back plies (letters A through D) and its exposure rating. A-grade plywood is the highest quality, but often the most expensive. Work with your lumber distributor to find the best grade for your project.
You may not know which side to show on a project when using premium grades of hardwood plywood—AA, A, and A1. Both sides may appear identical, but there are subtle differences.
The best side has even color, consistent grain, no flaws, and the fewest visible splices. In these photos, the top panel has fewer splices and a better grain pattern than the other premium-grade panel.
Grades of plywood differ by veneer quality, number, and the size of defects allowed. These are some of the most common grades, although other designations may be dealer-applied.
A-Premium: Sliced veneers matched for pleasing color and grain, one-piece rotary cut. Pin knots, small patches not allowed.
1-Good (cabinet grade): Unmatched veneers okay. No sharp contrasts in color, grain, or figure. Burls, pin knots, and small patches allowed.
2-Sound: No figure, color, or grain match. Smooth patches, sound knots, and discoloration or varying color allowed.