How far must a masonry chimney extend above a flat roof that is within 10 horizontal feet?

The requirement for a masonry chimney extending above a flat roof is intended to ensure that exhaust gases and smoke are properly vented away from the building and do not pose a hazard or cause issues such as backdrafting or obstruction. When a chimney is within 10 horizontal feet of a flat roof, it must extend a minimum of 2 feet above the roof surface. This guideline helps to ensure that any harmful gases are sufficiently dispersed into the atmosphere, reducing the risk of carbon monoxide buildup and improving air quality in and around the building.

The requirement for a chimney to extend 2 feet above the point where it intersects the plane of the roof is specified in building codes and standards, designed with safety considerations in mind. By ensuring that the chimney rises adequately above the roofline within this proximity, it allows for effective venting and minimizes the likelihood of flue gases being drawn back into the building. This is crucial for maintaining proper ventilation and safety in areas where chimney installations are common.