Plywood Ratings, Grades and Sizes

Plywood is sold in various ratings, grades and sizes. Make your selection based on the type of project you’re working on. 

Plywood Ratings: 

There are five important ratings that convey where and how to use plywood: Exterior, Exposure 1, Exposure 2, Interior and Structural 1.

Exterior means the panels have been waterproofed and can withstand inclement weather. Use exterior rated plywood for permanent outdoor structures that will be exposed to water long-term. 

Exposure 1 means the panels have been waterproofed and can withstand exposure to the elements during construction. However, they are not suitable for long-term exposure post-construction.  

Exposure 2 means the panels are made with an intermediate glue that is not fully waterproof. These panels can withstand occasional moisture but are otherwise intended for interior use. 

Interior means the panels are not waterproof and are designed for interior use only. They should not be exposed to moisture. 

Structural 1 is rated for seismic retrofit work, meaning it is designed to be earthquake resistant. Unless they have a Structural 1 rating, other plywood panels of any width are not suited for seismic retrofitting.  

Plywood Grades:

There are four grades of plywood: A, B, C and D. The grade refers to the quality and appearance of the plywood’s face and back veneers. A has the highest quality and is the most expensive, and D is the least expensive. 

A-grade plywood features a smooth, sanded surface without knots. Any wood defects have been repaired with synthetic filler, so the veneer can be painted. A-grade plywood is ideal for furniture or cabinet doors.  

B-grade plywood also features a smooth, sanded surface, but may have more repaired defects up to 1-inch across.

C-grade is unsanded and may have several minor defects that will need to be repaired with knots up to 1 1/2 inches across, discoloration and sanding defects. C-grade plywood should be used when appearance is not important, such as for subfloors or garages.  

D-grade is also unsanded with defects that have not been repaired and knot holes up to 2 1/2 inches across, discoloration and sanding defects.  

You may also find ratings with two-letter classifications, such as BC. BC-grade is a mix grade plywood with one side graded a B, while the other side is graded a C. 

Plywood Sizes:

The most common plywood sizes are 4- x 8-feet sheets and 5- x 5-feet sheets.  

Most places also carry pre-cut project panels that are available in different sizes that may vary by store. These project panels help eliminate waste, cut costs and are easier to transport than full-size panels.  

The most common thickness of plywood is 1/2-inch, but plywood thickness can range from 1/8-inch to 3/4 inches.