Different Types of Plywood and Their Uses
Plywood sheets are a man-made material manufactured by bonding three or more (always an odd number) layers (plies) of wood together to form a panel. Each layer’s grain is at 90 degrees to its neighbor before being glued, which helps prevent warping, shrinking, or expanding, giving the sheet its strength, and stability.
Plywood, like other timber products, is graded according to the quality of the panel’s face layer. There are four plywood grades, A, B, C, and D.
- Grade A is the best. The face layer is smooth and gives a quality painted finish.
- Grade B is not as smooth as Grade A and can contain minor flaws.
- Grade C can have knots in the panel.
- Grade D is the least costly, with knots and flaws on the surfaces.
Depending on the intended application, the different types of plywood include:
Softwood plywood is generally manufactured using Cedar, Douglas Fir, or Redwood, since these trees grow all year long, reaching maturity much faster. Used mostly in construction applications where strength and durability are needed, but a smooth surface finish is not.
Typical uses of softwood plywood are roof and wall sheathing, and sub-floor installations. The panels can range between 1/8 and 1-1/4-inch thick, although the most widely used are between 1/4-inch and 3/4-inch. The number of plies is governed by the grade and the thickness of the sheet.
For example, a 3/4-inch panel that can be bought at a home-improvement store is generally five-ply. Two face plies and three core plies. (Most DIY enthusiasts find this plywood the most economical to use). However, if the panel needs strength and increased bending resistance, seven, nine, or thirteen plies can be used and still have a thickness of 3/4-inch.
Common Uses of Softwood Plywood:
- Roof and wall sheathing
- Eaves and soffits
- General-purpose shelves
- Attic flooring
Hardwood plywood is made from trees such as Oak, Mahogany, Maple, and Beech. It is the plywood of choice when an attractive, smooth finished surface is needed such as in the manufacture of furniture and cabinets.
This plywood is usually graded as AB, where the face is grade A, the best quality, and the opposite face or the inside of the cabinet is grade B. If the project in hand involves any load-bearing or has the possibility of being exposed to the elements, choose plywood that has multiple layers, which produces a stronger, thicker board.
Usually three-ply is the most widely used indoors, five-ply can be used outdoors and indoors, but is not suitable for structural framing. Seven or more plywood layers can be used for framing, roofing, and other outdoor scenarios where stability and strength are needed.
Common Uses of Hardwood Plywood:
- Furniture manufacturing
- Built-in closets
- Kitchen cabinets
- Interior paneling
Tropical plywood, made from mixed tropical tree species like Teak, Ebony, and Mahogany, is denser, stronger, and higher quality plywood than softwood ply used where both face layers require a smooth finish. In many regions, it is the plywood of choice for construction purposes due to the low cost.
Common Uses of Tropical Plywood:
- Door frames
- Interior paneling
- Furniture and cabinet making
Aircraft plywood is a high-strength plywood manufactured from Spruce, Mahogany, or Birch, using adhesives that have a higher resistance to humidity and heat. The face layers or plies are hot-pressed together over a core of hardwood layers such as Poplar or Basswood, which is itself a type of aircraft plywood, but is more flexible and lighter than Birch or Mahogany.
Unlike general plywood’s minimum thickness of 1.8 mm aircraft plywood can be a mere 1 mm thick. Common sheet dimensions are; 4ft x 4ft, 4ft x 8ft, with other sizes of 50” x 50”, 59” x 59”, 60″ x 60″, and 61” x 61”. Being strong, and durable, with sheets as thin as 1 mm, custom-sized panels are easily cut to be used in the aircraft and marine industries.
Common Uses of Aircraft Plywood:
- Model airplanes
- Musical instruments
- Model boats
Decorative plywood, also known as overlaid plywood, is a premium grade ply where the face finish must be of the highest quality. The face layers have a veneer of hardwood such as Maple, Oak, Cherry, Walnut, or Teak, bonded to the rest of the plies by heat and pressure.
The finished surface is not always for decorative purposes, but to give the panel a surface that is hard-wearing, smooth, and is capable of preventing water or other things adhering to it. It is more expensive than other plywood because of the amount of resin it contains.
Common Uses of Decorative Plywood:
- Manufacture of cabinets
- Decorative panels
Flexible plywood is a non-hardwood plywood. As the name implies, it can be bent and flexed into various shapes, and is used in custom designs. The thickness of flexible plywood can vary from 3 mm to 16 mm depending on the end product.
Of course, the thinner the ply, the easier it is to bend into shape, so choosing the right thickness is vital to the success or failure of a project. Flexible plywood, combined with a quality veneer, can result in a beautiful end product. This type of plywood is used where quality is demanded.
Common Uses of Flexible Plywood:
- High-end desks
- Curved kitchen cabinets
- Construction of yachts
Marine plywood is not what the name implies. It isn’t waterproof. Marine plywood is manufactured using strong core and face veneers, from tropical hardwoods, that have minimal defects, giving the glue used a stable, solid bonding surface. The glue that is used in the manufacture of marine plywood is waterproof.
The reason the waterproof glue is used is in case the plywood be exposed to wet conditions, or extremely high humidity. The waterproof glue keeps the layers bonded together, preventing the plywood from falling apart. Marine plywood comes in various surface finishes depending on the wood veneer used.
For example, the Okoumé Marine plywood has a golden, honey-colored hue when finished with epoxy and varnish. Sapele (Sapelli) Marine plywood has a reddish-brown appearance, while Meranti marine plywood can vary in color from pale pink to reddish-brown. All colors and finishes convey quality.
Common Uses of Marine Plywood:
- Boat building
- Yacht interiors
- Piano cases
- Quality vehicle trim
Other types of plywood that are not commonly used but are available include:
Fire-retardant plywood is made resistant to combustion by a layer of chemicals that is strategically applied to the plywood in a manner that minimizes any discoloration leaving the wood’s natural color to shine through.
Moisture resistant plywood is made by using Phenolic resins as the bonding agent, giving the plywood a certain amount of waterproof properties.
This plywood has an overlay of multi-layer phenol film that has a coarse wire mesh pattern, mainly used as flooring. It is particularly good for floor panels of trailers as it gives a high-wearing, non-slip surface.
Sign-grade plywood is predominantly used for highway and road signs, combining the robustness of exterior-grade ply with the excellent wear of overlaid plywood.
Pressure-treated plywood is not as popular as others, but it can be obtained. Garden sheds are one example of where pressure-treated plywood can be used. Just as strong as other softwood plywood, but the chemicals that are injected into the wood mean it doesn’t need to be painted to keep it in prime condition.
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