Chimney Cap Chimney caps (aka flue guards or rain guards) help prevent rain water from entering the chimney and causing leakage in a house. But they also help prevent the deterioration of metal and masonry chimneys, vents, fireplaces and heating systems. Chimney caps can also help keep leaves, and other debris as well as birds, raccoons and other creatures out.
Metal chimneys and vents need caps to prevent corrosion of the metal. Even if stainless steel, caps are required. Manufacturers of prefabricated chimneys and vents supply the appropriate vent for their systems. Use of the improper type/size vent can result in venting problems that could lead to a fire. Restricted flow through a chimney or vent can also cause a backdraft and possibly the buildup of toxic carbon monoxide in a house.
While it was not common practice to add caps to masonry chimneys years ago, those without caps are more likely to have greater deterioration. Sometimes caps for masonry chimneys are made of slate or other masonry material, particularly if the flue did not have a liner; however, a less expensive approach is to install a cap designed for a masonry flue.
In areas of high fire risk or when there is a wood roof, chimneys caps should also have spark screening to prevent the spread of embers. Only caps and screening specifically designed and listed for this purpose should be used. It is important to periodically verify the integrity of the rain cap, especially after heavy rains and winds.