Choosing Plywood for Your Built-in

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.

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.

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.

Avoid boards with loose knots such as the one on the left. Loose knots often fall out as the wood dries, leaving a hole. Tight knots such as the one on the right are acceptable but need sealing.

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.