A masonry chimney flue liner should extend at least ___ and no more than _____ above the chimney top.

The recommended height for a masonry chimney flue liner is that it should extend at least 2 inches and no more than 6 inches above the chimney top. This specification is crucial for ensuring that the flue liner effectively directs smoke and gases away from the chimney and maintains proper draft.

Extending the flue liner at least 2 inches allows for adequate space for smoke to exit safely, preventing backdrafts and the potential for creosote buildup within the chimney system. The upper limit of 6 inches prevents potential turbulence and allows the chimney system to maintain a good draft. Additionally, having the flue liner extend too far above the chimney top could expose it to increased weathering and damage, which could compromise the integrity of the flue and lead to safety concerns.

This height specification ensures both efficiency in venting and safety for the structure and its occupants.