Plywood Grades: Understanding the Different Types and Their Uses

Looking for plywood for a project can be a daunting task. There are different plywood grades, finishes, wood species, and numerous kinds. Even though they’re labeled or stamped, selecting which is best for your project can be a challenge.

The best quality plywood is A or B-grade with C and D grades being less attractive but almost as structurally strong. Different wood species and adhesives also affect plywood strength and use. Those labeled with an ‘X’ are typically manufactured with waterproof adhesives and are more water-resistant and acceptable for exterior uses.

In this guide, we explain the different grades and types of plywood. We discuss their characteristics, quality, and uses, and identify which is the best quality plywood. Our aim is to provide you with the information to select the best material for your project.

Plywood Grades and Types

Plywood is manufactured from soft and hardwood veneer logs with alternate layers perpendicular to each other. This makes for greater strength in thinner materials as the grain of each layer alternates with that above or below it.

There are different adhesives used to bond the plies together and the glue determines if the panel can be used for interior or dry use or for exterior purposes, or both. Plywood commonly has 3, 5, or 7 plies, but can have as many as 21 or more. The more plies, the stronger and more stable the plywood.

In the US, plywood is identified as A, B, C, or D grade based on the quality of the surface veneers and its appearance and number of blemishes or defects. All manufacturers must follow the same grading system to ensure quality and strength. Grade A plywood is the best quality and appearance and D-grade is not so pretty.

Softwood plywood typically has two letter grades. The first letter refers to the grade of the face or top veneer and the second letter to the bottom or back veneer. Identification stamps are commonly on the end or edge of higher-quality plywood and on the back of lower-grade plywood, so as not to mar the usable face.

Plywood may be AA with high quality and appearance on both sides, AB, AC, through to DD, or utility grade on both sides. Plywood may also have an ‘X’ after the letter grades to denote that the plywood can be exposed to some moisture.

Some plywood may also have a numeric grade of 1 to 4, with 1 being the best and 4 not so good. The numbers usually refer to the quality of the back or bottom veneer. Most plywood species and types are in all grades and for exterior use, however, they may not be readily available everywhere.

There are also four classifications or types of phenolic or melamine adhesive bonds used in the manufacture of plywood that influence their use and type categorization. Interior use plywood has a Type C or D bond. It’s manufactured using a low-durability urea-formaldehyde glue that won’t prevent delamination if exposed to moisture or humidity and isn’t recommended for structural purposes.

Type B uses a more durable melamine-formaldehyde resin that is also known as MR or moisture-resistant. Type A uses phenol-formaldehyde adhesive and is often referred to as BR or boil-resistant adhesive. It stays strong even when exposed to moisture and temperature extremes and is commonly used for marine and exterior plywood.

A-Grade Plywood

The highest grade and quality of plywood is A-grade. It is usually sanded smooth and clear with no visible imperfections or flaws, so is the most expensive. It may have small knots up to 1/4” in diameter, but there are restrictions on the use of filler or patches for splits or blemishes.

The grade is the same for both hardwood and softwood plywood. It is ready to finish or paint and is typically used for visible decorative purposes or where looks matter. Often used for exposed flooring and wall or ceiling panels, plus cabinets, furniture, display boards, countertops, shelf units, and other quality products.

B-Grade Plywood

This grade is also mostly clear but may have football-shaped plugs or putty patches, but is otherwise smooth and ready to paint. There may be some tight knots up to 1” visible but no holes or missing pieces. There may be some minor splits that may or may not be filled.

Less expensive than A-grade, it is commonly used for the same purposes but often painted, not left natural. Ideal for cabinets, furniture, flooring, wall and ceiling panels, and other items. It is often manufactured as AB-grade for cabinetry purposes, so the outer visible surface is clear of blemishes and the inner surfaces are also smooth and easy to finish.

C-Grade Plywood

C-grade plywood may have small open knotholes up to 1” in diameter and tight knots up to 1.5” in diameter. There may also be some discoloration and splits. It may be labeled ‘C-plugged’ and have football-shaped plugs or putty-filled patches where open knotholes were.

It is commonly used for structural purposes like wall and roof sheathing and subflooring where a finished material will hide or cover it. It can also be used for storage shelving, workshop or garage cabinets and drawers, and other utility-type purposes. The smoother C-Plugged can be used for exposed painted surfaces instead of the more expensive A or B grades.

D-Grade Plywood

D-grade plywood may have large knots or knot holes up to 2.5” and some splits and wane, but typically there are no patches or repairs. It is the least expensive grade of plywood and is commonly known as sheathing plywood. From an engineering perspective, it has strong structural, compression, bending, and shear properties.

This non-appearance grade plywood is typically used for strength and is hidden or covered with more aesthetically appealing finishes. It is commonly used for sheathing walls and roofs and as subflooring. Due to its strength and lower cost, it is also used for rough cabinetry, shipping boxes, utilitarian furniture, work benches, and outbuildings.

ACX, BCX, CCX and CDX Plywood

Plywood graded for exposure (X) to moisture is manufactured using waterproof adhesives. Different grades of veneer are used on the top and bottom and determine potential uses. The first letter identifies the grade of the top veneer layer and the second letter the quality of the bottom layer.

ACX and BCX are often used for interior or exterior cabinetry and furniture, or visible wall, ceiling, or fence panels. The less expensive CCX and CDX panels are used for workbenches, shelves, subfloors, and sheathing walls and roofs.

WBP Plywood

WBP stands for Weather and Boil Proof plywood, not water and boil-proof. It is the highest classification of adhesion and means that the plywood is very durable and weather and moisture-resistant. WPB means the resin used is waterproof and will prevent delamination if exposed to moisture for extended periods. It is the only plywood category recommended by the United Nations for exterior use.

WPB bonded with regular melamine resin will withstand 4 to 8 hours of boiling water without delamination. Using high-quality melamine will improve that to 10 to 20 hours, while standard phenolic glue can retain lamination for up to 3 days. The duration, though, also depends on the grade of veneer used to make the plywood.

WBP is commonly used for exterior wall and roof sheathing, subflooring, outdoor furniture, and other construction uses. It is not as good as Marine plywood as it may have knotholes, cracks, and internal voids.

RTD Plywood

RTD plywood is manufactured in a similar manner to other plywood using waterproof resins, except that when heated and pressed to bond the layers together, a special tool is used. The tool is a Resistance Temperature Detector and ensures that the exact amount of heat necessary to activate the bond is used. This means the plywood is not only very strong but will resist delamination when exposed to moisture or boiling water.

RTD plywood may contain knotholes, voids, and cracks, so not visually appealing. It is often compared to CDX plywood but is more flexible and impact, moisture, heat, and cold resistant and less susceptible to delamination. This makes it ideal for subfloor use, wall and roof sheathing, shelving, and other uses. It also holds nails and screws well too.

Softwood Plywood

Softwood plywood is made of layers of different species from the fir, hemlock, spruce, and pine families, as well as redwoods and cedars. It may be stamped SPF or DFP, identifying that the plywood is made of spruce, pine, or fir species, or is Douglas fir plywood. It is commonly used for subfloors, wall and roof deck sheathing, shelving, packaging, as well as concrete formwork and other utility-like purposes.

The quality and grade of the veneers often determine the use or purpose of the plywood. A and B grades are used for decoration or in visible locations while C and D grades are used for construction and utility purposes.

Hardwood Plywood

Hardwood plywood is available in several formats. Less expensive and more readily available are panels with a thin hardwood veneer applied as the top and bottom layers of one or more layers of softwood veneer. The two hardwood veneers are usually A or B grade but the top may be one species and the bottom another.

The other type of hardwood plywood is usually made of 7 or more layers of birch, oak, maple, walnut, mahogany, or other species of wood. It is heavier and more expensive than softwood plywood of similar dimensions and is usually stronger and more durable.

Available in all grades, it is typically an A or B grade on the top and A, B, or C grade on the bottom. It is very sturdy and is often used for decorative panels, furniture, sports equipment, musical instruments, toys, shelving, or display structures. It’s also used in the manufacture of airplanes, boats, and automobiles.

Exterior Plywood Grade

Exterior grade plywood is usually multi-ply softwood plywood manufactured with weather-resistant and waterproof glues. It is a strong, durable product and better-quality exterior grades will last for decades.

There are different species of hardwood plywood that are also manufactured using similar adhesives. They are more expensive, durable, stronger, and will withstand more moisture, plus they are mildew and mold resistant. Exterior plywood is one of the most common grades.

Sanded Plywood

Sanded plywood commonly is used for cabinetry, shelving, furniture, paneling, or projects that will be visible. It is often labeled ‘AC’ with the sanded visible side being A-grade and the sanded back or bottom being C-grade. Most hardwood plywood is sanded while only some softwood plywoods are.

Pressure-Treated Plywood

Pressure-treated plywood is typically construction-grade plywood that has been treated in a chemical bath and pressurized to force the protective chemicals deep into the wood fibers. The chemicals protect the wood from moisture, insects, mold, and mildew so it won’t decay or rot when exposed to moisture or ground contact.

This type of plywood usually has a greenish or brownish coloring and can be used for fences, decks, wall sheathing, outdoor furniture, foundations, and most any other outdoor project. Some pressure-treated material has a bluish color and is specifically treated for water-resistant interior use such as bathroom walls and subfloors, or basement use.

Treated plywood that is pinkish in color has a higher fire rating and is used where combustibility is a concern.

Construction Grade Plywood

Construction grade is also known as structural or sheathing plywood. It is strong, durable, and inexpensive softwood plywood designed for building permanent structures. Both surfaces are C or D-grade and are typically used for subflooring, sheathing walls, and roofs, and are usually covered or hidden by other materials. Due to the knotholes and voids, they don’t handle extended exposure to moisture and the elements well.

Furniture Plywood (Cabinet Grade)

A variety of different high-quality plywood can be used to make furniture, including EuroPly, Baltic-birch plywood, and ApplePly. ApplePly or Apple plywood is manufactured in the US and designed for furniture and cabinet making. It is usually hardwood plywood made of more layers of thinner veneers from birch and alder, but similar types of quality hard or softwood may be used.

The veneer layers are often formed using strips of different species laminated together before being bonded together with other similar plies. The multiple thin layers of laminated wood make for a strong, sturdy, lightweight panel that won’t check, tear, splinter, or fuzz when cut or drilled. It also has a smooth texture and appearance and takes stains and paints well.

Shop Grade Plywood

Shop grade plywood is commonly factory seconds or shipping damaged interior or exterior panels that cannot be sold as A to D graded plywood. It is also known as mill-certified plywood and may have started out as AA or other grades but due to handling or other damage caused at the mill can’t be so labeled. Depending on the original grade of plywood and damage, it can be used to make beams, shipping boxes, furniture, cabinetry, toys, crafts, or thousands of other purposes.

Baltic Birch Plywood

Baltic birch plywood is made of multiple thin layers of A or B-grade birch so there are no hidden voids. The multiple thin layers make it stronger and lighter than typical thicker veneer plywood, as well as giving it a more aesthetically appealing edge profile.

Baltic birch also has superior screw holding ability due to the multiple layers of birch veneer. Although available in 4×8 sheets, it is typically manufactured in 5×5 panels for use in the European cabinet-making industry.

Aircraft Plywood

A high-grade and durable plywood typically of hardwoods like mahogany or birch which can withstand both moisture and heat. It is commonly made of thinner veneer layers, making it stronger, lighter in weight, and more workable.

Often used for building aircraft, boats, rafts, and heavy-duty furniture or machinery cabinets. It is an industrial-strength plywood also used in buildings or structures requiring stronger, more durable materials.

Marine Plywood

Marine-grade plywood is manufactured to withstand extended periods of time submerged. It uses phenol-formaldehyde adhesive, the same waterproof adhesive as CD-X or exterior grade plywood, but all plies are A or B-grade, not just the top and bottom. This ensures that there are no holes or voids in any layer where moisture could be trapped and cause rot.

Marine plywood may be all hardwood plies, all fir or larch, or softwood with hardwood veneers like oak, mahogany, or teak on the top and bottom. Marine grade plywood is one of the highest grades of plywood if not the highest grade. It can withstand heavy rains, full emersion, and all temperature ranges.

It is used for boat hulls, frames, and decks, as well as outdoor furniture, countertops, cabinetry, porches, planters, playhouses, boathouses, and most any project susceptible to moisture exposure.

Flexible Plywood

Flexible plywood is also known as Hatters Ply, Flexi Ply, Curve-Ply, bending plywood, and Wacky or Wiggle wood. It is a specialty plywood that can easily be bent or curved into different shapes without separating, cracking, breaking, or losing strength or stability. It has no resistance to rolling, bending, or twisting.

The inner plies are usually thinner cross-grained veneers and the outer layers are thicker cross-grained plies. Some are manufactured using imported hardwood plies with the grain in different layers all in the same direction. The panels aren’t made for exterior or structural use.

Flexible plywood is commonly used for chairs, furniture, arches, columns, cabinetry, stairs, skirting, or finishing.

Tropical Plywood

Tropical plywood is imported from different Asian, African, and South American countries. It is manufactured using tropical hardwood species like teak, ebony, and mahogany but looks similar structurally to North American softwood plywood. However, it has more consistent layer thickness, superior strength, and a density greater than A-grade plywood, giving it better structural performance, appearance, and value.

Lumber Core Plywood

Lumber core plywood usually has only three layers. The two outer layers are usually thin hardwood veneers of oak, maple, walnut, birch, or other species. The inner core is a single thicker veneer layer of softwood made by gluing strips of wood together to form the required width. The result is a sturdy wood panel that holds nails or screws better in the softwood core than a solid hardwood panel would.

Moisture Resistant Plywood

Moisture-resistant (MR) plywood is bonded together using waterproof adhesives. It will resist humidity and moisture but isn’t waterproof. There are different varieties of MR plywood, such as ABX, ACX, ADX, BCX, CCX, and CDX. The first letter identifies the top ply grade, the second the bottom ply grade, and the X denotes that it can withstand exposure (X) to moisture.

It is manufactured to withstand some exposure to water or moisture and prevent damage caused by water seepage into the layers. This makes it ideal for humid climates where wood swelling can cause issues. Plus, it is more resistant to insect and termite damage, and doesn’t have the leaching or off-gassing issues of pressure-treated plywood; making it ideal for multiple interior uses.

There are several other types of moisture-resistant plywood. BWP or boiling waterproof plywood is also known as marine plywood and is manufactured using adhesives that can withstand extended periods of moisture exposure without delaminating.

BWR or boiling water-resistant plywood is made of thin layers of veneer and is engineered to resist moisture and can resist boiling water. Both BWP and BWR are used for indoor and outdoor furniture manufacture, boat building, and numerous other purposes.

Overlaid Plywood

Overlaid plywood is either medium or high-density plywood that is more durable and scratch-resistant. Manufactured in a similar way to other plywood using waterproof adhesives, but the veneer plies are coated with more resin adhesive.

The layers are also bonded together using higher heat and pressure, resulting in a smooth, more water-resistant material. The top veneer layer is often birch, oak, mahogany, teak, or another quality hardwood. The high-density plywood uses more resin than the medium, and so is more expensive.

Oriented Strand Board (OSB)

OSB is a less expensive engineered plywood panel made of thin leaf-like strands of soft and hardwood. The strands are soaked in wax-resin adhesives and oriented so the inner mat-like layer goes one way and the outer layers in an opposing direction.

The whole mass, which may be up to 50 layers thick, is then heated and pressed to the desired thickness, ensuring a consistent density and no voids. OSB is often used for sheathing walls and roofs, as well as for subfloors and beams.

What Is the Best Quality Plywood?

The best quality plywood has AA-grade veneer identification. The higher the grade, the better its appearance, with A-grade being clear with minor or no visible defects.

It is ideal for decorative accents, wall and ceiling panels, exposed flooring, cabinetry, furniture, shelving, and other items or uses that require a smooth wood surface or look. It can be stained or painted, and depending on the type of plywood, used for numerous other purposes.

Hopefully, you have a better understanding of plywood grades and types and better are prepared for your next project.