Clay bricks FAQ.

Clay bricks are a natural product that is made purely of only clay. Its totally inert chemically and is one of the hardest man made building material. It is normally fired to over 1000 degrees Celsius to vitrify the clay. Once it is cooled, its behaves like stones, albeit a rectangular stone.

Function of Clay Bricks.

The main function of clay bricks in Malaysia is non structural. That is, unless specified by the structural engineer of a specific strength of the bricks, the most common use of clay bricks is partitioning. For partitioning purposes, the strength required by SIRIM is 7N/mm2.(MS 2282-1:2014,AMD.1:2016) Clause 5.3.4.

Colour of clay bricks.

The colour of the bricks has no bearing on the quality of the bricks. The colour comes from the minerals found in the clay itself during its high temperature firing. Examples of common minerals found in the clay that colour the bricks are iron oxide (red colour), bauxite (white colour) and Magnesium (brown to black). The colour variation may also come from how close the clay bricks in from the fire. Normally, the closer it is to the heat, the darker will be the colour of the brick.


The surface of the bricks may have marks or spots on them. These are normally the results of the minerals like silica melting and moving to the surface of the bricks. They can also be due to the ash of the fuel melting on the surface of the bricks. These harden dark marks are indelible and they do not Affect the quality of the brick or will discolour the plaster in anyway. It just proves that the brick is well fired.

Dark Core.

Some clay have high organic materials in them and some manufacturers adds fuel like palm shell or coal into the clay during manufacturing to assist in the firing process. In both cases, the center of the brick, core, may be black or darker in colour. The darken core is due to the fuel burning inside the brick without oxygen, technically called reduction firing. Again this darken core is totally inert and does not affect the quality of the brick or the darken colour will seep out to discolour plaster.


It must be noted that clay is a natural product and its composition varies constantly. Some bricks may vary in sizes even from the same manufacturer. The sizes may vary due to the position they are in the kiln and how close they are to the fire. The closer they are to the heat source, the more they may shrink. The clay from the ground also changes from place to place and from different depth. This constantly changing landscape keeps changing the composition of the clay and their shrinkage behavior.

Surface Cracks.

Again some clays may have some surface cracks. Most of these cracks comes from the stacking of the bricks during firing. The different shrinkage of the bricks can sometimes cause some of the bricks to crack. As these are generally surface cracks, they will not affect the integrity of the clay bricks. To be certain of the strength, a comprehensive test in an authorized laboratory is recommended. Throwing of bricks to the ground is not a recommended way to judge the strength of a brick.