What is Plywood?
Along with concrete blocks and lumber, plywood is one of the main staples of residential and commercial construction. Plywood is made from thin wood veneers or "plies" that are then glued together, pressed and heated to form sheets. The wood grain of the plies are rotated 90° with each alternate layer to reduce expansion and contraction of the wood. This gives plywood stability and resistance to shrinkage, breaking, warping, and cracking.
The Plies of Plywood
The layers of veneer or plies of the plywood help determine the strength of the sheet. Plywood must have a minimum of three plies and are usually combined in an odd number of layers. The most common plies are:
- 3-ply is one of the most common types of plywood. With three layers of veneer it's strong and durable. It can be a good choice for indoor use with a more decorative look than plywood with more layers.
- 5-ply refers to the five layers of veneers. This is common type of plywood that is suitable for a wide range of miscellaneous and construction uses where rigidity and strength are needed.
- Multi-ply plywood is mostly for exterior use and roofing. Usually designed with seven or more layers, it creates a very strong, durable home frame material that will withstand wind and weather damage.
Plywood Grades
Plywood receives grades (ranging from A to D) based on the number of blemishes on the product.
Grade A: Both the face and back are nearly free of defects, with a smooth, sanded surface and virtually no knots. Ideal for cabinet doors and furniture and can be painted or stained.
Grade B: Also sanded smooth, but the face and back have a few defects. These blemishes may have been repaired filler. Cheaper than Grade A.
Grade C: Unsanded, with tight knots up to 1-½-in width. Larger sections that have been patched and filled. Good for subflooring or other applications where appearance is not important.
Grade D: Also unsanded, with knot holes up to 2-½-in width. Generous patching and filling with some unrepaired defects. Like Grade C, good for structural uses where it will not be seen.
When two grades are indicated, such as A/B, the A refers to the face and the B refers to the back. This can save costs to the mill. The most common is B/C-grade, which is a mix of B-grade on the face side and C-grade on the back side.
