Types of Plywood

Plywood is an engineered wood from the manufactured boards family which includes particle board and oriented strand board (OSB). It is made from thin sheets of veneer peeled from debarked trees. These thin layers, also called plies, are glued together at alternating right angles to create a cross-grain pattern. This pattern adds strength and stability that resists shrinkage and expansion caused by moisture.

Plywood is a popular choice in construction because of its strength and low cost. It is used in areas hidden from view that offer support such as floors, walls and roofs in residential construction.

When used for roofing, plywood panels are covered and protected by other materials that keep the elements at bay, including roof felt, underlayment, flashing and shingles. When used in flooring, plywood creates a subfloor that supports hardwoods, tile and carpet floors.

Stainable and paintable plywood is ideal for shelving, cabinets and furniture. Outside the home, plywood can be transformed into fencing materials, packaging materials, scaffolding, sheds and shipping crates.

There are several common types of plywood:

Sanded plywood features face and back (top and bottom) plies that are sanded in the manufacturing process. It is used in places where the wood surface is visible, such as cabinets, shelves and paneling.

Hardwood plywood has outer layers made from hardwoods like birch, maple and oak. It can be heavier than other types of plywood.

Plywood sheathing or structural plywood is designed for permanent structures. It is strong and less expensive than sanded or hardwood plywood, but doesn't have a finished appearance. When a house frame is built, sheathing is added to provide shear strength. It becomes an integral part of the structure and provides a substrate for the attachment of siding and roofing materials.

Most plywood is offered in several sizes. The most common size is 4x8 feet, which is often referred to as a "full sheet." This is the most economical way to buy plywood. Sheets can be heavy and of course, they're big, and will not fit in cars or SUVs. Check with your local Home Depot about cutting services or truck rental, if needed.

Project plywood panels are smaller sizes, usually 2x4 feet or 2x2 feet. They're easy to grab from the store and cary home in a car, no need for a pickup truck. There are various types of wood, ply and plywood alternatives available.

A ply refers to a layer of wood used to create plywood’s various thicknesses.

The material that makes up the plies and the thickness of each individual ply varies across different grades and usage types of plywood.

Just like all wood, each ply has a grain direction. Wood is strongest across its grain. Plywood gets its strength and stability by alternating grain directions when the sheet is made. Outer plies have the grain direction running in the long direction of the sheet, inner plies alternate between the short and long dimensions.

Sheathing plywood has fewer layers and a rough surface because its intended use is to cover framing and roof decking. It provide's a nailing surface for finish materials but its most important function is to provide shear strength to a building's frame.

Outer layers on higher grades of plywood are called veneers. These veneer plies give the appearance of high quality hardwood and can be stained, clear coated or painted.

Higher grade plywood, intended to be used in cabinetry and furniture, has a higher number of thin layers. This provides more stability, keeping the plywood flatter.

Tip: Plywood with fewer plies is weaker than a plywood with more plies, even if they have the same thickness.

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 by pressure treating 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. These panels will hold up to several wet-dry cycles during construction because the glue is water resistant. 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 4x8 foot sheets and 2x4 foot sheets, commonly called "project panels."

Thickness ranges from nominal sizes of 1/16-inch to 3/4-inch.

You can use other types of boards in place of true plywood. They may even be commonly referred to as plywood, despite being manufactured differently. Although not technically plywood, other engineered wood boards and panels can be great options for construction projects when you want to save money or have a different look and feel.

When choosing plywood or a plywood alternative, consider these features as well:

Oriented Stand Board, or OSB, is made by gluing chips of wood together under great pressure. This is used as sheathing and roof decking in rougher forms. OSB is also available in a smooth form with tongue and groove edges for use as subfloor. Some companies make specialty OSB with weather-resistant coatings or other useful features.

Medium density fiberboard, or MDF, is a heavy sheet product that is made from compressing fine wood dust with resin. It is smooth and machines well. The finished surfaces take paint well but cut surfaces and edges need to be sealed before painting. MDF shouldn't be allowed to get wet, a small amount of water exposure will damage it.

Markerboard tempered hardboard, particle board, wall paneling and more are also in the same area of your local Home Depot store.