How many inches must clay flue lining extend above the enclosing walls?

The correct answer is that clay flue lining must extend a minimum of 8 inches above the enclosing walls. This requirement is crucial for ensuring that the chimney or flue system functions correctly and safely. The additional height helps to create sufficient draft, which is essential for the proper venting of combustion gases and smoke from the fireplace, stove, or furnace.

Having the flue lining extend above the surrounding structure also serves to prevent any potential hazards, such as downdrafts or the accumulation of debris, which could obstruct airflow. Furthermore, this requirement is typically outlined in building codes and standards, reflecting established practices in residential construction to promote safety and efficiency in chimney and flue design.

It is important for contractors to be aware of and comply with such specifications, as failing to do so can lead to functional problems with the heating system and increase the risk of fire.