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Plywood Grades Explained

While buying plywood from a dealer, have you ever been stumped by the word 'grade'? Plywood grades explained in the following article will help you understand the types of plywood and purchase the right ones that suit your needs.
DecorDezine Staff
Plywood
The thin sheets of wood that are glued together in layers, such that the wood grain is at a right angle to each other is called plywood. Different types of plywood are graded according to an engineered wood panel. You will find that the grades used are in the range of A, B, C, D and N. These gradings are based according to the number of blemishes on the plywood, indicating their quality. The best quality plywood is graded N, which is used very rarely. N grade is said to have the least number of blemishes, followed by A, B, C, and D. The plywood grades explained in detail in the following paragraphs will help you with your woodworking task better.
Grades of Plywood
As you have understood from the above paragraph, A, B, C, and D are the grades that are commonly used. When you have a look at the plywood, you will find the letter grades are printed in pairs. These grades explained here, will help you understand their hidden meaning. This means, if one side is printed with A and the other side with C, it indicates that the plywood has a well-finished front side and a slightly unfinished back side. Construction grade plywood is graded as C-D and called CDX plywood. The best way to explain grades of plywood is by understanding the types. Let us have a look at the four basic types of plywood.
Types of Plywood
There are different plywood sizes and types available in the market used for different purposes. The explanation on types of plywood will help you understand the use of these woods in home construction better.
Interior Plywood
The interior plywood is available in different grades and the common grades are A-C, B-D, etc. It is used for construction within the house. They cannot be exposed to moisture and are bonded with agents that give away when exposed to the elements of nature. Thus, these plywood should be kept away from wet areas and never kept outdoors.
Structural Plywood
Structural plywood is available in grades such as C-D and D-D only. These are rough plywood pieces that are used for cement forms. They are glued together with adhesives that hold the layer firmly. It can be used in any area where you do not mind the looks of the rough plywood.
Exterior Plywood
The grades of plywood in case of exterior are A-C, B-C and CDX. Exterior plywood is glued together with adhesives that are meant to survive in wet or moist areas. They are used in the construction of a house exterior region or outdoor furniture.
Marine Plywood
The marine plywood is only available in A-A grade. It is the strongest, toughest and the best quality plywood you can ever find. It is glued together with superior quality adhesives that bind tightly and is resistant to water. It has both sides finished as it comes in A-A quality. It is used for construction of outdoor furniture, and other areas where you want the plywood to look good as well as remain weather-resistant.
Marking of Grades
Plywood is generally available in 4'x8' sheet and is cut into a square board. The thickness of plywood normally used is 1/8", 1/4", 1/2", and 3/4". The 1/8" and 1/4" plywood is used for making hard covered flats. 1/2" plywood is used for building furniture parts, boxes and props. It is lighter as well as cheaper than 3/4" plywood. Lastly, 3/4" plywood is used to make covering platforms as it is very strong type of plywood.
Plywood Grades Chart
The following plywood grades explained with the help of the chart will make things regarding the type and their uses clearer.

Interior Plywood Grades
Plywood Grade Front Side Back Side Inner Plies
Underlay C Plugged D C, D
C-D C D D
B-D B D D
A-D A D D
A-B A B D
A-A A A A

Interior Plywood Grades and Their Uses

Underlay: This plywood is used as an underlay for carpets as well as tiles on an uneven sub floor.

C-D: This plywood is used for structural as well as sheathing of sub floors and shuttering.

B-D: This is a utility-grade plywood with only one side that can be painted.

A-D: This is a finish-grade plywood used for making furniture.

A-B: This plywood has one face that is finished grade and the back face has no voids and is very smooth.

A-A: This is finish-grade plywood on both sides si used for making domestic furniture, cabinet doors, etc.

Exterior Plywood Grades
Plywood Grade Front Side Back Side Inner Plies
C-C C C C
C-C Plugged C Plugged C C
B-C B C C
A-C A C C
A-B A B C
A-A A A C

Exterior Plywood Grades and Their Uses

C-C: This plywood is used for rough building work and shuttering. The unsanded C-C grade can withstand heavy exposure to weather.

C-C Plugged: This plywood is used for backing tiles and wall coverings. It can also be used for high performance coatings.

B-C: This plywood is used for landscape and general building uses like fences and shuttering. It is also used for base coatings.

A-C: These are for soffits and facias as well as used for base coatings.

A-B: This has just one side as finished grade.

A-A: This has both sides finished grade and is used for making the structure look more beautiful.
The interior plywood sheet needs to be used for construction of furniture within the house, while the exterior is meant for outdoor use.