Should new clay bricks be left to dry out before use?

Clay bricks expand fractionally after leaving the kiln (primarily due to moisture in the air) and minute increases in height and width (0.006 percent per annum) continue at a decreasing rate for up to 5 years.Fortunately with clay products the majority of this expansion happens almost immediately the product leaves the kiln and is exposed to atmosphere.

In the good old days all the bricks would be purchased at the beginning of a project and stored for many months before being used. It was thought this gave them an opportunity to harden and "dry out".  Today, purchases are JIT (just-in-time) and the timing from order email to delivery to use is less than a week. The age of bricks in stock will vary considerably from factory to factory and region. Obviously if product is in high demand they do not stand too long in the yard before delivery.

There are many sources of movement in walling and paving including ambient moisture levels, temperature, loading and creep, chemical action, ground movement and settlement. For more information, please download the "Movement of Brickwork" technical paper.