Chimney Cap Problems

Metal Chimneys

• The cap on a metal chimney will keep the rain out. Without a cap, the rain will run into the stove, fireplace, or heater and can ruin walls and ceilings. Birds and other animals can nest in the chimney, blocking it. Metal chimneys have layers of metal with insulation between them; if water gets between the layers, it will cause rust and shorten the chimney's life.

Replacing the Cap on Metal Chimneys

• Metal chimneys always come with a termination cap. When replacing it, try to find the manufacturer so you can get the cap specifically for that chimney. At times, you may need to install a different type of cap -- for example, when you have a draft problem or cannot locate the manufacturer. If you have draft problems, specially made caps are designed to use the wind to create a stronger updraft.

  If you don't have draft problems and just need a replacement cap, but can’t locate the manufacturer, you can often use a cap from a different brand as long as it fits properly. Monitor the cap closely for a while after installing to make sure there are no problems. Some metal chimneys have venting at the top to air cool the chimney, if you have this type chimney, do not to close off the venting slots on the top. If you do, a house fire could result from heat buildup. Special caps are available for these chimneys to assure proper cooling. Make sure your replacement cap will work properly for your chimney, for safety if for no other reason.

Masonry Chimneys

• Masonry chimneys do not necessarily need to be capped. Most people find that the advantages of a cap far outweigh the disadvantages.The disadvantages include: draft restriction from an improperly designed or installed cap; a clogged screen from soot and creosote that build up over time; discoloration of exterior bricks from creosote and tar; caps blowing off in high wind and being destroyed or then needing to be reinstalled (All About Chimney Caps, Masonry Chimneys and Fireplaces). The advantages include: keeping animals from nesting in the chimney; keeping out rain and moisture; keeps ice from the top of the chimney, which will eliminate cracking of the flue tile; increases draft of chimney to keep smoke out of the house (All About Chimney Caps, Masonry Chimneys and Fireplaces).

  Deal with the disadvantages of a chimney cap easily by burning hard wood to eliminate creosote, fastening the cap securely so it will not blow away, or changing the design if you have a draft problem. The advantages of not having rain or critters in the chimney are significant compared to the disadvantages that may or may not result from having a chimney cap.

Replacing the Cap on a Masonry Chimney

• For masonry chimneys, most people use a steel cap with screening around the sides to keep birds and small animals out. Specially made caps to solve draft problems increase the chimney's updraft. These are the same as for metal chimneys. Caps also are custom-made for odd-sized chimneys or multiple flues. If you have a fireplace, you should have no problem finding a cap that functions well for your chimney.