Plywood Is a Manufactured Board of Odd Number of Thin Sheets of Wood

Plywood is a manufactured board of odd number of thin sheets of wood. These sheets are known as piles or veneers. They are glued together under heat and pressure. The number of sheets used is odd, because the bottom and top sheet should have the same grain facing in the same direction. The grains of each sheet go length-ways on one layer and cross ways on the other and so on. This helps the plywood become strong in all directions, as opposed to standard wood, which is strong only across the grain.

Different Grades of Plywood
Plywood can be made from softwood and hardwood and have multiple uses. It is used for wall panels, bracing, wood flooring, home furniture, cabinetry, etc. Plywood is also available in different grades. It is stamped with a grading stamp that comply to the National Plywood Standard PS 1-83 in America. The plywood grading system uses letters A, B, C and D. The A grade stands for the best quality plywood that has no blemishes and is well sanded. D stands for the lowest grade plywood that has maximum number of blemishes. You may even find some stamped with paired grades. For example, a plywood with A-C, refers to a plywood whose one side will have a very good finish and the other side will be comparatively unfinished back. If you are using construction grade plywood, then it may be marked C-D. It is commonly known as CDX plywood that is good for structural use, but not as a finishing material. Let us know more on different types of plywood.

Different Types of Plywood
There are different plywood types available in the market that are used for specific purposes. There are also different conditions under which different plywood are used. There are four basic types of plywood bonding types. The difference in the plywood bonding is because of the glue used to bind the sheets of the plywood. Let us see the different types of plywood according to bonding types:

• Interior Plywood: The interior plywood is used for construction that is carried out inside a house. These plywood are not meant for external use, as they cannot stand excess moisture. They are bonded with agents that are not suitable for harsh elements of nature, thus, cannot be kept or used for outdoors or areas with high moisture. The common grades in which interior plywood is available is A-C, B-D, etc.
• Exterior Plywood: The exterior plywood is glued together with a gluing material that can withstand moisture. Thus, it is used for constructions carried out outdoors or areas of little moisture. The exterior plywood is available in many grades and the common ones are A-C, B-C and CDX. The CDX grade plywood is the most common construction grade plywood found in DIY centers and stores.
• Structural Plywood: These are extra strong plywood planks that are glued together with an adhesive that holds the layers firmly. The structural plywood can be used for internal or external purposes. These are not meant to be seen and are mostly hidden behind other constructions. The construction crew uses it in cement form and it can be used anywhere that needs a strong structure and you don't care about the looks of the plywood. The structural plywood is available only in C-D or D-D grades, making it one of the toughest plywood,
• Marine Plywood: The marine plywood is fabricated with a superior glue that is bonded tightly and resistant to water. It is the strongest, toughest and highest grade plywood. The marine plywood is available in only A-A grade, thus making it suitable for both side finishes. It can be used to finish a basement flooring with high moisture content or outdoor furniture and other weather resistant, finished surfaces.

These were a few types of plywood that were differentiated by their bonding types. The following different types of plywood are differentiated on the basis of their usage and the material compositions.

• Medium-Density Fiber Core Hardwood Plywood: The MDF core hardwood plywood is a stable material and good for working and every batch is consistent. It means that if you purchased a 3/4" thick sheet 4 years back, the new sheet you purchase today will be of exactly the same thickness. It is made from fine wood dust, mixed with a binder and heat pressed into panels. The drawback of this sheet is its weight and a 3/4" x 4' x 8' sheet can weigh about 70 to 90 pounds per sheet.
• Medium and High Density Overlay Plywood: This sheet is made of fir veneers at the core and wrapped with fiber. It is considered to be an ordinary veneered cored plywood coated with MDF. It has a sturdier surface and found to be more durable. It also weighs less than MDF plywood.
• Veneer Core Hardwood Plywood: This different type of plywood is made of alternative layers of common plywood. The surface of the plywood is veneer and has a grainy wood finish like maple or oak. This plywood is stronger than other plywood and easy to work on due to its light weight.
• Lumber Core Plywood: This plywood is made of hard wood pieces like base wood and the core is surfaced and layered with veneer. The lumber core plywood is the most expensive of all plywood and is used in applications that have edges which cannot be concealed and exposure is the only solution.
• Particle Board Core Plywood: This plywood is the made from coarse dust as compared to MDF and is a light weight plywood, not consistent and smooth. Many melamine products have PBC used as a substrate.
• Melamine Plywood: These are plywood that are fused thermally and have a resin saturated finish. The melamine plywood is the most abrasive and stain resistant plywood. The grade of melamine depends on its use and is flexible for many applications. Melamine plywood is smooth, coarse and can be soft or brittle.

Plywood Sizes
The plywood sizes available are rather very confusing in nature. You may find hardwood and softwood plywood that are sold as four feet wide, but are sometimes found in two and five foot widths. You may also see the common length of a plywood sheet is 8', but you may come across four and twelve feet sheet lengths. The length and width are somewhat understandable, but I found the thickness dimension very puzzling.

In America, 3/4", 1/2" and 1/4" are the most common plywood sizes available. But, a 3/4" plywood size should be labeled (now they have actually started to label it) as 23/32", 1/2" as 15/32" and 1/4" as 7/32". This slight difference becomes an issue during construction work. For example, if a person who is into woodworking, needs to put up 1/2" plywood shelf into the dado cut of the shelf standard, then he will find a noticeable gap making the shelf slightly sloppy in the dado. So, the woodworker will have to cut the dado at 15/32" to make the shelf fit without any sloppiness.

The common varieties of softwood plywood are available in three, five and seven piles. Their length and breath dimensions are 1.2 m x 2.4 m (4 feet x 8 feet). The thickness dimension is 1/8 inch. For roofing you may use plywood sizes available in 3/8 inch. The floor boards are at least 5/8 inch in size, depending on the floor joists distance.

There are different types of plywood based on their thickness. Normally, plywood thickness ranges from 1/8" to 1-1/4". The thickness of some of the common plywood types is given in the table below:

This was a little information on the plywood sizes and types. Dad explained me the difference between the sizes and types and I can now answer all the dumb plywood questions thrown at me by my ever boasting brother. I hope you too find some valuable information from my article. I have tried my best to explain the different sizes and types of plywood. In the end, I will just thank my big bro, whose constant jeering, made me learn a valuable information on different types of plywood and plywood sizes available.