Plywood is a sheet material manufactured from thin layers or “ Plies “ of wood veneer that are glued together with adjacent layers having their wood grains rotated upto 90 degrees to one another. It is an engineered wood from the family of manufactured board which include medium – density fibre board ( MDF) and particle board (chip board).
A plywood sheet having ISI mark photographed at a carpenter’s shop in Navi Mumbai, India. The IS specification number IS:303 is mentioned above, and a CM/L number (Licence number) is mentioned below the ISI mark.
All plywood bind resin and wood fibres sheets to form a composite material. The alteration of the grain is called Cross- graining and has many benefits.
It reduces the tendency of wood to split when nailed in at the edges. It reduces expansion and shrinkage, and makes the panel strong in all directions. There is usually an odd number of plies, so that the sheet is balanced- this reduces warping. So providing stiffness to the board.
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Types of Plywood
Basic Type :
1) Commercial MR grade for internal use.
2) Waterproof BWR grade for exterior use.
3) Marine Plywood.
Types of wood used:
- Hard wood – Harder and Stronger
- Soft wood – Lighter and weaker
- Flexible Plywood that can bend.
- Film- faced shuttering plywood for Industrial use.
- Structured Plywood for Industrial use.
- Fire retardant Plywood – Internal and External grade plywood.
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Internal for indoor use.
External- waterproof, used outside.
Furniture- Commercial plywood used is internal MR (Moisture resistant) grade.
BWP ( Boiling Waterproof).
BWR – Boiling water resistant are called exterior grade plywood. They are made using phenolic resins and are adequately waterproof.
Marine plywood are superior grades of ply and superior to commercial ply. They are more expensive.
They are not used for furniture making. These are used for boat building and other Industrial uses when there is prolonged exposure to water.
Suggested Read: What is MDF (Board/Wood) – Its Uses & What it is Made of
Plywood mainly used are
Hardwood plywood – made from teak – gurjan wood, birch wood.
If all veneers are made from hardwood it is called 100 % hardwood plywood. The cost is higher.
Soft wood : made from cedar, SPF ( Spruce-pine-fir) or Mango wood.
Plywood Types according to Trees
- Gurjan Plywood
- Teak Plywood
- Red wood Plywood
- SPF Plywood
Flexible Plywood this also called flexiply, it is not stiff. It can be rolled up.
It is used for creating rounded shapes in furniture.
Fire resistant It is used in public theatres, malls, shopping complexes, and Restaurant kitchen. The surface is coated with chemicals to delay the burning process.
Marine Grade: For Boats and Ships
It is most resistant to water.
Termite Resistant and Borer proof :
It is protected from Termites and borer.
Structural Plywood for construction application where structural stability is important.
Suggested Read: What are Advantages and Disadvantages of MDF Board
Concrete Shuttering plywood.
It is used to help settle concrete in building.
Film – faced shuttering plywood
It has a shiny phenolic film over the surface so that the concrete does not stick to the plywood. Plywood is decorated using laminates, paints, polish, veneer.
Decorative Laminates such as Sunmica or others (which are actually a blend of paper and plastic) are glued over the plywood surfaces. Laminates are available in a very wide variety of colours, patterns and textures, and is the most common way of decorating plywood furniture and panels.
Paint has for long been a way of protecting wood and increasing its beauty. It is a low-cost alternative to laminates or veneers and a large choice of wood colours are available.
Suggested Read: MDF vs. Plywood vs. Particle Board
Wood Polish is usually used on wooden furniture that is made of quality hardwoods such as teak, however polishing plywood is not uncommon. Carpenters often use wood polish (of darker colours) on some parts of furniture (such as the underside of tables and the inside planks of single and double beds).
Wood veneers are thin slices/sheets of quality woods such as teak, which can be glued over the plywood surface to increase its beauty and make it look richer. Most casual observers cannot differentiate between a piece of solid teakwood furniture and one that simply has a teak veneer on the outside. Veneers are usually the costliest way of decorating plywood.
So we see that plywood is a very essential material in indoor and outdoor extension work. It is multipurpose and extremely useful and niche material.