Do It Yourself and Other Educational Chimney and Fire Safety Articles

A Chimney cap is more than a decorative ornament that sits on the top of your chimney.  It is also a safety feature that keeps out obstacles such as smoke and animals from entering your home.  If your chimney is missing a chimney cap or the top of the chimney cap too close to your chimney end, this could inhibit your chimney’s draft, which is what draws air from the fireplace and allows the fire to stay light nicely without allowing smoke to enter your house.  A cap also keeps out debris such as fallen leaves, wetness from falling rain or melting snow, and any pesky animals such as raccoons that could try to enter your chimney.  Water is very destructive to the interior of your chimney because it can cause cracks in the liner.  Another obstacle some chimney owners face if they have a double flue chimney is smoke from the first flue can travel back down the second flue if a cap is not there to properly redirect the smoke.  This can happen from wind or if the first flue terminates lower than the second.  The best way to make sure your chimney cap is operating properly is to get close and inspect.  You need to get on the roof and make sure it is undamaged and connected properly with the flue to prevent any fire hazards from entering your chimney.

If you determine that your chimney cap needs to be replaced because it is damaged, non-existent, or not connected properly to your chimney termination, here are some steps to install a chimney cap:

1.    Get out your ladder and climb onto your roof.

2.    Identify the type of chimney flue that you have because it will dictate the chimney cap you can install.  If you are not sure what type of flue you have, take a look inside your chimney and decide which of these descriptions below that best matches what you see.  Or, take a picture while on the roof and bring it to your computer to compare to the listed flue types below.

3.    Ok, so the first step you need to follow is you need to determine if you have a masonry chimney or a factory built prefabricated chimney. 

4.    Then determine your flue situation and use the descriptions below as a guide.  At this point, if you determine that your chimney does not have a flue, you need to stop and hire a professional chimney sweep to install a flue prior to choosing a new cap.  Your chimney is not upholding current safety codes and cannot be used until a flue is installed first.

5.    Finally, you can take measurements and decide on the type of cap that is best for your chimney.  Measure the inside diameter of your flue.  It is important to know that the flue can come in many different shapes; they can be round, oval, square or rectangular.  The cap dimensions will fit these measurements. 

6.    If your chimney is prefabricated, you should identify the manufacturer and model information of the pipe at the same time, if you want a factory replacement or you have a metal chimney that requires it.

7.    When you make your measurements, take a pencil and paper with you when you go up to your roof. Nothing is more frustrating than winding up with the wrong size chimney cap because of a incorrect measurement.  Measure at least twice to make sure your measurements are accurate before you place an order on a new cap.  This will save you a lot of work later if you had the wrong size.  If your chimney system does not match any of the descriptions provided in this guide or you're still unsure of what to measure, ask a professional chimney sweep.

a.       Here are some descriptions of masonry chimneys and their liners:

                                                               i.      Single-Flue Chimneys with an Extended Flue- A chimney with a single flue that extends above its crown. Extended flues are amongst the most common and easiest to cap because the cap can be directly attached to the flue with clamps or screws. If you have this type of chimney all you need to do is measure the length and width of the outside of your flue. Then you can simply search for a chimney cap designed to fit those dimensions.

                                                             ii.      Single-Flue Chimneys without an Extended Flue- The flue in this chimney is completely flush with its crown. Capping one of these chimneys requires either a standard single-flue chimney cap with legs or brackets or a top-mounted model. If you want to install a chimney cap with legs or brackets you'll need to measure the outside width and depth of your flue. Then, as when looking for a chimney cap for an extended flue, you can search for a model designed to fit your specifications.

                                                            iii.      Single-Flue Chimneys with a Flexible Metal Liner – A soft round metal tube that is flexible and sits within the chimney.  When capping this kind of chimney, you have to use a slip-in model cap. Finding a chimney cap for this type of flue is very simple. Just measure the inside diameter of your flue and search for a cap with that diameter.

                                                           iv.      Multi-Flue Chimneys- A chimney that has more than one flue.   This kind of venting system requires a top-mounted chimney cap regardless of whether the flues are extended or not. Measuring for a top-mounted cap that attaches directly to your crown is more complicated than the previous models. Start by measuring the entire length and width of your chimney. Then measure the length and width of the area that contains your flue.  And, finally, measure the height of each flue.  Depending on your goals, you can either choose to get a chimney cap big enough protect your entire chimney.  Or, you can get one that covers just the area surrounding your flues. Regardless of which kind of coverage you want, your cap must be at least five inches taller than your tallest flue.

b.       Here are some descriptions of Factory-Built Chimneys:  In all cases, it is best to use the matching cap that is made by the same manufacturer that designed your prefabricated chimney because they highly specialized to work together.

                                                               i.      Double-Wall Air-Insulated Chimneys- The double wall chimney has two pipes within each other.  There is an inner pipe and an outer pipe separated by open space that allows air flow to cool the flue. Because they are so specialized, it's best to use a chimney cap produced specifically for your brand of double-wall air-insulated vent pipe. The diameter of the chimney cap you choose needs to be the same as your pipe's inner diameter; a pipe with a seven-inch inner diameter, for example, requires a seven-inch chimney cap.

                                                             ii.      Double-Wall Solid-Pack Insulated Chimneys - Double-wall solid-pack insulated chimneys also feature an inner and outer wall, but rather than air, it uses insulation to separate the two pipes. In some instances the insulation is left exposed, while in others it is covered with a metal cap. Both varieties require a chimney cap specifically designed for that type of double-wall solid-pack insulated pipe. As with air-insulated models, it's best to use a cap produced by the same manufacturer as your pipe.

                                                          iii.      Triple-Wall Air-Insulated- These work just like double-wall air-insulated pipes and require a specialized triple-wall chimney cap made by the same manufacturer.

                                                          iv.      Triple-Wall Solid-Pack Insulated Chimneys - Triple-wall solid-pack insulated pipes feature three walls separated by insulation. This kind of chimney requires a cap specifically designed for triple-wall insulated pipe and, as with other types of metal chimney pipes, it's best to use the one produced by the same manufacturer.  Even though these chimneys have three walls, you only need to know the diameter of the inner and outermost ones. Your pipe's inner diameter is the number you need to match when selecting a chimney cap; a pipe with a six-inch inner diameter, for example, requires a six-inch chimney cap. The outer wall of your pipe also needs to be covered by your cap, but it doesn't matter if your cap extends beyond the edges of your pipe.

Now that you have determined the type and size of chimney cap that you need, you can place your order.  Once it arrives, you can install it by screwing it in or if it not the type that screws in; inserting it and applying a silicone sealer.