What is the required clearance of a joist from the back of a masonry chimney?

The required clearance of a joist from the back of a masonry chimney is 4 inches. This regulation is in place to minimize the risk of fire hazards. When a wooden joist comes too close to a masonry chimney, there is an increased chance that heat radiating from the chimney could ignite the wood, particularly if the chimney has not been adequately maintained or if there are flammable materials nearby.

The requirement for a 4-inch clearance helps ensure that there is a sufficient buffer zone to mitigate these risks. This standard is often outlined in building codes and guidelines to promote safety in construction and renovation projects involving chimneys and joists. Understanding these clearance requirements is crucial for builders and contractors to comply with safety regulations and reduce fire risks in structures.