What Is the Difference Between #2 Plywood & Premium Grades?
Plywood is a ubiquitous construction material, used in everything from roofing, flooring and walls, to cabinetry and furniture. There are hundreds of types of plywood. Different grades of plywood are identified by a letter and number combination. Numbers refer to the grade on the back of the plywood, while letters refer to the front. The American National Standards Institute (ANSI) has codified basic requirements for plywood to meet No. 2 back grade. Does this Spark an idea?
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Tight Knoks
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To obtain No. 2 back grade classification under ANSI, a 4-by-8-foot sheet of plywood can have up to 16 natural, tight knots that are a maximum 3/4 inch in diameter. ANSI requires no more than 16 tight knots on No. 1, or premium, back grade plywood that are a maximum 3/8 inch in diameter.
Knot Holes
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No. 2 plywood must have all knot holes --- where pieces of wood have dropped out of the face of the wood during production --- repaired. Premium grade can have no knot holes, whether repaired or not.
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Repaired Knots
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No. 2 back grade plywood can have up to eight repaired knots that are a maximum 1/2 inch in diameter. Premium back grade plywood can have no repaired knots.
Tigh Burls
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Burl refers to swirls and changes in the direction of the wood grain. ANSI allows both No. 2 and premium grade plywood to display burling, provided the grain is intact and the surface remains cohesive.
Minerals and Sap
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ANSI provides both back grades of plywood to demonstrate minerals and sap, which often stain the wood during production and can only be prevented by extensive drying and curing techniques used for more decorative lumbers.
Joints or Splits
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According to the way in which plywood is manufactured, it must have joints to achieve any significant size. The ANSI allows up to six repaired splits or joints on the back veneer of both No. 1 and No. 2 grade plywood.
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References
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