There are a variety of ways in which plywood is classified and these classifications are usually based on the different aspects of plywood such as the wood used, the number of plies it has, its suitability for indoor and outdoor use, its grading as per quality specifications, and its intended uses.
In this article we will have a detailed look at the different types of plywood available.
If you visit any of the plywood shops in your locality and ask for the types of plywood available, the most likely answer that you can expect to get is that there are two types, commercial and marine. Some dealers also will say that there are waterproof types available.
THE MAJOR TYPES OF PLYWOOD
INTERIOR AND EXTERIOR GRADE PLYWOOD
As the names suggest, interior grade plywood is meant for indoor use, while exterior grade is waterproof and can be used outdoors. The most common type of plywood that is used for making furniture for our homes and offices is Commercial plywood (which is Interior MR grade). The acronym ‘MR’ stands for ‘Moisture resistant’.
BWP (Boiling Water Proof)or BWR (Boiling Water Resistant) plywoods are called exterior grade plywoods. They are made using phenolic resins and are adequately waterproof.
COMMERCIAL , WATERPROOF AND MARINE GRADE
When dealers in India say Commercial ply, they mean MR grade, and when they say ‘Water proof plywood’ what they generally mean by that is BWP/BWR grade plywood. However there are many shopkeepers as well as interior designers who often refer to BWP/BWR grade plywood as ‘Marine ply’ as this has become sort of a naming convention in the plywood market. (however technically speaking this is incorrect, since the actual ‘Marine grade plywood’ is different from BWP/BWR grade waterproof plywood. Its of a superior quality and used in marine applications).
The Indian Standards quality specification for all these so-called commercial plywoods is detailed in the document IS: 303. Plywood companies that have a BIS (Bureau of Indian Standards) certification are allowed to have the ISI mark printed on their plywood sheets. The IS specification number has to be printed above the ISI mark, and the CM/L number (Unique LicenceNumber)is printed below the mark.
Marine Plywood is of a superior quality compared to Commercial ply and it is also costs a lot more. It is not usually used for indoor applications such as for making furniture. It is rather used for applications such as for boat building and other industrial uses where the plywood is bound to get a prolonged exposure to water.
For making furniture, commercial plywood is usually sufficient.(BWP/BWR resist water better than MR types. So for kitchen furniture using BWP/BWR is quite common). For furniture that is unlikely to get wet, MR grade ply is usually good enough.
The Indian Standards quality specifications for marine type of plywood are described in the standards document IS: 710.
Types Of Plywood Based On The Type Of Wood Used
Generally hardwood is used for making plywood, because it is stronger and more durable, however some manufacturers may also use softwood for making lower cost plywoods. Still other manufacturers can use a combination of both woods, with some wood veneers of hardwood and others of softwood.
For example made from teak wood, or gurjan wood or birch wood. If all the veneers used in making the plywood have been obtained from hardwood trees it will be termed as 100% hardwood plywood and its cost will be higher.
For example made from woods like cedar, SPF (Spruce-Pine-Fir) or Mango wood.
Categorization based on the particular wood (tree) used in its making.
More Terminology And Usage Based Classifications
MR grade: Moisture Resistant
The most common type of plywood used for indoor furniture. Note that moisture resistant does not mean water proof. It only means that the plywood can resist a certain amount of humidity or dampness.
BWR And BWP Grades
The BWP (Boiling Water proof) grade is generally used to indicate grade of External grade blockboards (which are different from plywood and consist of blocks of softwood at the core) and BWR (Boiling Water Resistant) grade is used to indicate External grade plywood. Both these naming conventions BWP and BWR mean almost the same thing in terms of quality. Such types of plywood can be called adequately water-proof for most furniture requirements.
Also called ‘flexi ply’ in India. In some countries such as US, it is also known by another name ‘bendy ply’. This type of plywood is not stiff and can be easily rolled up. Useful for creating rounded shapes in furniture.
FR Grade: Fire Retardant
Used in places where fire risks have to be reduced such as in the case of public theatres, malls or shopping complexes, restaurant kitchens and the like. The surface of this type of plywood is treated with chemicals that delay the burning process of wood (hence called fire retardant). Indian standards document number IS: 5509-1980 has detailed quality specifications for this type.
Marine Grade: Marine Grade Plywood
Commonly used for marine applications such as in the construction of boats and ships. Has better resistance to water than any other type of plywood. Indian Standard specifications for marine ply are detailed in the IS document number IS: 710
Termite-Resistant And Borer-Proof
As the name suggests, offers protection from external pests that can destroy the wood.
Suitable for construction applications where structural stability is required.Quality specifications detailed in document IS: 10701
Concrete Shuttering Plywood
Used in building construction work to create the wooden moulds into which concrete will be case. Hence called concrete shuttering plywood. Can be reused several times before being discarded or used for other purposes. Indian standards specified in IS: 848-1974
Film-faced shuttering plywood has a shiny phenolic film over the surface, so that the concrete does not stick to the plywood, and the dampness does not damage the ply.
Classification Of Plywood Based On Size, Thickness And Number Of Plies
Plywood sheets are made by bonding several individual wood veneers (plies) together. Veneers are thin layers of wood usually obtained by rotary cutting timber logs obtained from trees. Rotary cut means that the logs are rotated along their longitudinal axis using machines, and a cutter peels layers (slices) from the log while it is being rotated. These thin slices of wood (called veneers) are then pressed and bonded together using phenolic resins.
A plywood sheet is made up of at least 3 veneers (plies) if not more.
- 3 ply
- 5 ply
- 13 ply etc.
(Number of plies are always an odd number)
When more number of veneers are used, the thickness as well as the cost of the plywood increases.
- 18 mm ply
- 19 mm ply etc.
Standard size sheets are manufactured by most manufacturers across India. While thickness is usually measured in mm (metric system), the prevalent naming convention for sheet sizes is still in feet. Prices are also based on cost per sq.foot.