by Tom


by Tom


Single Flue Chimney Cap - Measure

How to Measure for a Single Flue Chimney Cap
to Fit a Square or Rectangular Flue:
Single Flue Chimney Cap Measure Guide


Single flue caps attach to the flue. For chimneys with a single square or rectangular flue, select a chimney cap like those shown below. Some single flue chimney caps that attach to the flue with clamps. The majority of single flue chimney caps, however, attach to the flue with set screws that press against the flue.

Chimney Cap Measure - HY-C Adjustable Clamp Chimney Cap Single flue chimney cap that attaches to flue with set screws
 Attaches to Flue with Clamps  Attaches to Flue with Set Screws

Here are examples of chimney caps for single flues that attach to the outside of the flue with screws:

What to Measure for a Single Flue Chimney Cap

To measure for a single flue chimney cap, measure the outside length and width of your flue.

What to Measure for a Single Flue Chimney Cap If the Flue Does Not Stick Up at Least an Inch

If your single flue does not stick up at least one inch, you can use either a top mount chimney cap (also known as a multi-flue chimney cap) or a single flue chimney cap with a set of “legs.” The legs fit down inside the chimney flue and securely hold your chimney cap in most situations. We do not recommend the use of chimney caps with legs especially in areas with high winds. A top mount chimney cap is always a more secure choice if your single flue does not stick up at least an inch.

Single Flue Chimney Caps with Legs

•     If your flue does not stick up at least one inch and you want a chimney cap with legs, measure the outside length and width of your flue.

•     If your flue does not stick up at least one inch and you want a chimney cap that mounts to the top crown on your chimney, follow the measuring directions for top mount chimney caps (also known as multi-flue chimney caps.)

Top-Mount Chimney Cap on Single Flue Chimney

Top Mount Chimney Cap on a Single Flue Chimney


Which Metal is Best for a Single Flue Chimney Cap?

Single Flue chimney caps are manufactured from stainless steel, copper, and galvanized steel.

•     Stainless steel is the best value for the dollar. Stainless steel is the preferred metal for salt water climates.

•     Copper is the most elegant, especially for historic or upscale homes. Copper is not recommended for light colored chimneys.

•     Galvanized steel is the least expensive and the least durable.

Stainless steel and copper chimney caps come with a lifetime warranty. Some stainless steel caps can be powder coated with black or colored with heat resistant finishes. Galvanized steel chimney caps are painted black.


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  1. Al Colley November 18, 2015 at 12:46 PM - Reply

    Hey, does any company have any engineers over twenty five years of age??? What about houses with chimneys that were built back in the late twenty’s or in the 1930’s as mine was. I don’t think the builders knew anything about these ceramic liners that all the designers have based their products on in every listing I have found here on-line. Will we all have to have a metal shop build the units for us because the suppliers on-line aren’t old enough to know what products are really needed by the public? One of my neighbors looked for some units for his single flu chimneys and he finally gave up and went up each year and put a sheet of thermal plastic over his, but its a hassle for him to do that but it works. I am not physically able to do that myself and I will get them custom made even though all I want is a plain black raised cap with a screen in it so my furnace will have an outlet for its burner smoke can get out, but I wanted two because a pair would look better than a mismatched pair would. Not one, not even a single one had any of these listed even as an option. Its mostly the older houses like mine and a lot of my neighbors with houses in this Historic neighborhood who don’t want to change the looks of their houses and the chimneys really add to the beauty of the houses and those with caps are really neat looking. None of us want to pay through the nose to have some custom built by a metal shop because they can’t build them a couple at a time for anything like the price that you can sell those built by a factory that is set up for doing that kind of work on a production line basis. Do you know of any company we could order from that builds the units that fit the chimney and not the ceramic liner inside the chimney? It seems to me that anyone who needs to put a ceramic liner in a chimney needs to go back to school and learn about chimneys. A ceramic liner is a heat thief!!

  2. David Huff August 15, 2016 at 3:31 PM - Reply

    How does the Forever Cap mount. Our clay tile flue is 13 1/2 X 13 with rounded corners. The flue tile sticks up about 4 inch above the cement chimney cap.

    • Tom January 4, 2023 at 10:42 PM - Reply

      David, screws go through the base of the Forever Cap and tighten against the straight sides of the clay tile flue. The chimney cap has an interior “shelf” that sits atop the clay tile flue.

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