By Abhijit Phadke
Blockboard sheets can be classified based on their composition, quality, the wood used in its making, and properties such as size and thickness etc.
Based on their quality and suitability of use, the two main types of blockboards are:
1. Interior Grade:
Suitable for indoor use, such as for furniture used inside the home or for doors.These types are also called MR grade (Moisture Resistant) blockboard.
2. Exterior Grade:
This type of blockboard is suitable for outdoor use and it also known as BWP or BWR grade blockboard. BWP stands for Boiling Water Proof and BWR stands for Boiling Water Resistant. Superior quality adhesives are used in making these exterior grade blockboards compared to the MR grade ones, so that the sheets can have better resistance to water.
The naming convention mentioned above is similar to that used for plywood in India. The Indian Standards document IS:1659 has detailed specifications regarding the manufacture and quality testing of interior and exterior grade blockboards.
Classification based on the wood used for the blockboard core
At their core, blockboard sheets are made up of solid blocks of wood (also called strips or battens). These solid wood blocks are placed adjacent to each other lengthwise across the board and then the front and back surfaces of the board are covered with hardwood veneers. (usually a single sheet of 4 mm ply on each side). These core blocks are almost always made from softwood obtained from softwood trees (e.g. Pine wood is very popular in India).
While softwood core is the most common, some manufacturers do manufacture blockboards that have a core made from hardwood strips as well as hardwood veneers on the outside. Such types of boards are classified as hardwood core blockboards, and they are denser, heavier, stronger and also generally costlier.