Plywood's strength and flexibility make it useful for a wide range of jobs.
Plywood is an exceptionally versatile building material because several layers can add strength and flexibility to your construction job. External plywood is bonded with an external glue and is graded based on the quality of its appearance and finish. Each plywood board is assigned two letter grades from A to D that correspond to the quality and finish of the two faces of the board.
A-A
Exterior plywood with a grade of A-A is unblemished and thoroughly, evenly sanded on both sides of the board. A-A grade plywood is typically used when both sides of the board are going to be fully visible from the exterior. A-A grade plywood is also used in any circumstance in which you are concerned with moisture resistance, since sanded finish free of cracks allows for minimal moisture infiltration.
A-B
A-B grade plywood is similar to A-A plywood in that it has been finished and sanded on both sides. The difference between these two grades is that A-A plywood is free of blemishes, whereas A-B plywood has one blemish-free face and one face that may be discolored or marked. A-B plywood is used when both sides of the plywood will be visible, but the appearance of one side is more important than the other.
A-C and A-D
Unlike the top two grades of A-level plywood, A-C and A-D plywood features one sanded, unblemished side and one side that is unfinished and not sanded. A-C and A-D plywood is used for jobs in which only one side of the finished product is visible.
B-B
B-B grade plywood is a lesser grade of finished plywood that can be used when both faces of the plywood will be visible. It is typically used for jobs in which the plywood will be painted to hide minor blemishes in the wood.
B-C and B-D
Similar to the lower grades of A plywood, B-C and B-D plywood contains one finished face and one unfinished face. The finished side will contain blemishes and other imperfections. This grade of plywood is commonly used in agricultural construction for which appearance is not a critical factor.
CDX
C-C and C-D grade plywood, collectively known as CDX plywood, is the most basic grade of exterior plywood on the market. Both faces of the board are not sanded; they may be marked with blemishes, splits, and cracks that do not affect the structural integrity of the board. They have typically been bonded using exterior glue. CDX plywood is typically used for temporary construction jobs that don't favor aesthetics and in places that are likely to be assaulted by foul weather, such as decks and balconies.
