By how many feet must a masonry chimney extend above any portion of a building within a horizontal distance of 10 feet?

The correct answer indicates that a masonry chimney must extend a minimum of 2 feet above any portion of the building within a horizontal distance of 10 feet. This requirement is in place to ensure proper ventilation and safety, as it helps prevent the escape of harmful flue gases into the living space. Additionally, a chimney that is elevated adequately reduces the risk of downdrafts, which can cause smoke and gases to enter the building instead of being expelled safely.

The 2-foot extension also aids in maintaining adequate clearance from nearby structures, ensuring that heat from the chimney does not pose a fire hazard to adjacent materials. This regulation is often outlined in building codes and industry standards to promote safe construction practices for chimneys.