Plywood can be used for furniture, wall panelling, cabinets and more. It is not only a versatile material, but also inexpensive and relatively environment-friendly (waste is confined to the small core and bark that remain after peeling away the strips and veneers). Certain kinds of plywood, such as structural or boiling-water resistant (BWR) types, can be used in exterior applications too, as they are very strong and resistant to hot, humid conditions.
What is plywood?
It is a manmade material made out of the wood of different trees, the most popular being oak, poplar, birch and walnut. The logs are chosen for their straightness and roundness. For the actual manufacturing process, thin strips of wood are laid in alternating directions and bonded with glue into strong, sturdy sheets. The stack is then heated and pressed to form a rigid panel of varying thicknesses, and the final product is laminated.
The advantage of this process is that the panels turn out to be very strong. Wood is 25-45 times stronger along the grain than across the grain. The strength of each plank of plywood is uniform in either direction. In plywood, the grain of each ply runs at right angles to that in the next one, ensuring uniform strength in either direction. Plywood is, therefore, also less susceptible to expansion and shrinkage.
The quality and grade of plywood determines various factors governing its use: the weather exposure that it has been approved for, the maximum distance it can span and the species of wood used for the face veneer. It is also graded for exterior/interior applications depending on the water-resistance of the glue used.
Types of ply
Plywood is commonly available in thicknesses of V inch, N inch, W inch, K inch, X inch and 1 inch with square, tongue-and-groove (planks can be set alongside and dovetailed into each other) and shiplap (planks must be fitted overlapping each other slightly) edges. Sheets are available in 4x9ft, 4x10ft and other sizes. However, 4x8ft is the most commonly used.
In terms of the bonding and structure, there are two types of plywood: marine and structural. The former is treated with special adhesives that make it water-resistant and is ideal if you’re looking for a material that isn’t affected by moisture. The second does not have the best finish, but when strength and stability are your first priority, structural plywood is preferred: The resins used here are designed for superior strength in order to prevent separation of layers from wear and tear.
Besides marine plywood (MR), there is another grade of moisture-resistant plywood, known as BWR plywood. While MR plywood is used exclusively for interior furnishings, BWR can be used in interiors as well as for exterior applications. As the name suggests, BWR does not delaminate even if immersed in hot water for more than 8 hours. This makes it particularly suitable for the hot and humid conditions.
Additionally, there are specialized varieties of plywood tailored for specific needs. Take, for instance, shuttering plywood: It is not only boiling-water resistant, but also imbued with extra strength and is resistant to termites and fungi.
A special form of shuttering plywood, called film-faced plywood, has an improved resistance to abrasion and fungi, and is also easy to clean.
Another option is flexible plywood, which (as the name suggests) can be moulded to take on a variety of shapes.
Now that you’ve chosen the best for your requirements, ensure that the wood used is ISI-certified. Sana S. Vishwanath