When two or more flues are located in the same chimney, what is the required minimum thickness of the masonry wall between the flues?

The minimum thickness of the masonry wall between flues in the same chimney is specified to ensure adequate separation for safety and structural integrity. A thickness of 4 inches provides a sufficient barrier that helps prevent the transfer of heat and gases between the flues. This is crucial to avoid potential fire hazards and ensure efficient operation of the vents. Additionally, a thicker wall contributes to the overall strength of the chimney, reducing the risk of structural failure due to thermal expansion and contraction.

In the context of building codes and safety standards, maintaining a distance that allows for safe operation while minimizing the risk of flue gas leakage is a critical consideration, making 4 inches the appropriate requirement.