Classification of Bricks

These bricks can broadly be divided into two categories as follows:

1. Unburnt or sun-dried bricks
2. Burnt bricks

The unburnt or sun-dried bricks are dried with the help of heat received from sun after the process of moulding. These bricks can only be used in the construction of temporary and cheap structures. Such bricks should not be used at places exposed to heavy rains. The bricks used in construction works are burnt bricks and they are classified into the following four categories:

1. First class bricks
2. Second class bricks
3. Third class brick
4. Fourth class brick

First class bricks 

These bricks are table-moulded and of standard shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. They comply with all the qualities of good bricks which are mentioned earlier. These bricks are used for superior work of permanent nature.

Second class bricks

These bricks are ground-moulded and they are burnt in kilns. The surface of these bricks is somewhat rough and shape is also slightly irregular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brickwork is to be provided with a coat of plaster.

Third class bricks

These bricks are ground-moulded and they are burnt in clamps. These bricks are not hard and they have rough surfaces with irregular and distorted edges. These bricks give dull sound when struck together. They are used for unimportant and temporary structures and at places where rainfall is not heavy.

Fourth class bricks

These are overburnt bricks with irregular shape and dark colour: These bricks are used as aggregate for concrete in foundations, floors, roads, etc. because of the fact that the overburnt bricks have a compact structure and hence they are sometimes found to be stronger than even the first class bricks, It is thus seen that the above classification of bricks is based on the method of manufacturing or preparing bricks.