The chimney is an exposed area of a home, which is why it is important to make sure that it is built correctly and will last. The most common type of brick to use to build a chimney are calcium silicate or clay bricks.
If clay bricks are used the resilience of the bricks will depend on three factors that are related. These are the mortar, the durability designation, and the detailing of your chimney.
Chimneys are exposed on all four sides and on the top, so brickwork is typically saturated. This means that they will be exposed to sulphate attack and frost more than other areas of the building. For this reason, it is recommended that you put a capping or coping on the top of the bricks in order to reduce the exposure to moisture.
Mortar is important when it comes to chimney construction as well. The durability and the risk of saturation will determine the appropriate type of mortar to use. Sulfate resisting cement is most often recommended because of the soluble sulfates in the condensation from flue gas.