Variations in Brick Size
Bricks are man-made components manufactured from a naturally occurring material, so they will never be precisely the same from one brick to the next. In addition, different parts of the kiln will vary in temperature, and this can also affect the extent to which the brick shrinks during firing. It is common, therefore, for a dimensional variance to occur within a batch of bricks, with length being the most significantly affected. This variance in size is a key factor in brick quality. In the representative sample of twenty-five bricks in Fig 34, the vast majority of bricks conformed to the required size of 215mm or just below. Larger size variations and/or a greater number of bricks that stray too far from being 215mm will cause practical problems for the bricklayer, particularly, among other things, in maintaining a consistent cross-joint thickness. Bricks that display such excessive variations could end up being classified as ‘seconds’.
Fig. 34 Dimensional variance in a sample of twenty-five bricks extracted from a larger batch.