How To Understand Plywood Grade?
Plywood grade means the quality of the face veneers and exposure classification. There are basically five grades for veneer. The grades run from A, which is the highest, to D. The reason why there are five grades is C grade has two grades C and C plugged. If you see an "N" grade, it's basically an A or better. These grades describe the appearance and plywood strength. The grades specify how many knots and patches and other imperfections the plywood can have.
Each sheet will have two grades, such as AB. The first letter stand for the face veneer grade and the second is for the back veneer. Some plywoods have a third letter, X, that designates them for exterior use.
A: Smooth, paintable surface with no knots and no surface repairs.
B: Similar to “A” but may contain tight (not loose) knots up to 1 inch and may include repairs (made with wood putty or football-shaped wood patches).
C: May contain tight knots up to 1 1/2 inches, as well as surface repairs.
D: May contain large and/or loose knots, voids without surface repairs, splits and other flaws.
The exposure classification indicates the allowed exposure to moisture for the plywood. Interior plywood, suitable only for protected, interior use, receives an exposure grade of INT. Exposure 1, or EXP 1, allows exterior exposure to the elements for a limited period of time during construction. Exposure 2, or EXP 2, also called IMG, allows less exposure to moisture or humidity. EXT is for exterior applications that include permanent exposure to the weather.