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Chimney Cap Sizes (Measurement Guide)

Here’s the different chimney cap sizes available including standard chimney cap dimensions and methods to measure for the perfect chimney cap fit.
Brick chimney with metal chimney cap on a black metal roof with skylight window and dormer windowPicture this: wintertime, the snow is falling, you have the fire crackling, and there is an orange glow around your living room, but then suddenly there is a sound coming from your fireplace, and then a loud, falling sound as debris and twigs and snow come cascading out your fireplace.

What you need to avoid that problem in the future is a chimney cap. Read on and find out more.

Are Chimney Caps Standard Size?

Chimney caps come in different shapes and sizes, so there is no definite chimney caps size, although there are the “usuals” or more common sizes of chimney caps.

For masonry chimneys made of bricks or stones, the common dimensions are 8 by 8 inches or 8 by 13 centimeters for smaller chimneys. There are 13 by 13, 8 by 17, or 13 by 17 inches for bigger fireplaces’ chimneys. 

It’s essential to measure for your chimney caps because if they don’t fit perfectly for your chimney, it might not be effective in doing the work. 

Standard Chimney Cap Size

13x13 inches chimney capThe sole purpose of a chimney cap is to act as a covering on your chimney to protect the fireplace. Aside from protecting your chimney from water from rain or snow, it also keeps the embers and sparks in the fireplace. Chimney caps are usually made of weatherproof materials like steel or copper mesh. 

For every standard size of chimney cap, a corresponding chimney size will make the cap a perfect fit. For typical 8 by 8 inches chimney caps, it would fit a 6.25 by 8.5 inches chimney size perfectly. There are also 8 by 13 inches chimney caps that would fit chimneys 6.25 by 11.5 inches and chimneys 8.5 by 13.5 inches in dimensions. 

Bigger chimneys 11.5 by 11.5 inches or 13.5 by 13.5 inches in dimensions would require a chimney cap with a size of 13×13 inches. Another is chimneys with sizes that range from 11 by 16.5 inches to 13.5 by 18.5 inches would need chimney caps 13×17 inches in size. 

How Thick Should a Chimney Cap Be?

Asphalt roof with masonry brick chimneyIn order to work perfectly and to be durable enough no matter the weather and wear and tear, a chimney cap should be 2 inches or 5 centimeters thick all over.

Aside from protecting the chimney from any water damage, chimney caps also keep out twigs, leaves, and whatever trash the wind manages to carry.

If dirt accumulates in the chimney, it could lead to a blocked flue that could cause harm not only to your chimney but also to your health. There could be an accumulation of carbon monoxide that could cause respiratory distress when breathing. 

How Tall Should a Chimney Cap Be?

Chimney heightFor a chimney cap to be effective, a chimney cap needs to be at least 8 inches or 20 centimeters above your chimney’s flue tiles that it will be covering.

You can even go longer than this, but don’t go lower than 8 inches or 20 centimeters. Going lower might interfere with the workings of a chimney draft. A chimney draft directs smoke out of a chimney. 

What Size Chimney Cap Do I Need?

The perfect chimney cap is the one that has a close size to both the inside and outside measurement of your chimney flue. Also, remember that your chimney cap should be higher than the flue in order for the chimney to work as it should. 

How To Measure For a Chimney Cap?

There are a variety of methods to measure for the perfect chimney cap to fit your chimney. It all depends on what your chimney style is. The easiest by far is measuring a chimney cap for a single flue chimney. All you need to do is gauge your chimney’s outside length and width. 

Step. 1 The first step is measuring the length of your chimney flue from top to bottom. You do that by measuring from the chimney crown to the flue on top. 

Step. 2 After that is done, measure the flue pipe diameter from the inside from one edge to the other. 

Step. 3 After measuring the inside, measure the outside of the flue pipe just like you did on the inside. 

Step. 4 Use the measurement you have to choose the best chimney cap. The best chimney cap will have a similar or relative size to the inside measurement of your flue pipe.

The chimney cap will be close to the size of your flue, especially if you have an industrial chimney that is usually made in a thinner material. 

If you have an oval flue that extends to an oval chimney, what you will need is a top mount style chimney cap. Measure for a chimney cap by assessing the size of the length and width of the flue. 

If you have a flue that is not extended and is not high enough for a flue mount cap, what you need to do is acquire a chimney cap leg kit that will still allow you to use a flue mount cap for your chimney.

This leg kit will be attached to the insides of the flue. Although it requires more work, this type of cap will work best in windy places. 

Brick house with stone coated metal roof tile plastic windows rain gutter and modular chimneys with rain capThere are chimneys with multiple flues, and no matter how short or extended the vents are, it will require a top-mounted chimney cap.

The tallest flue height is measured because your chimney cap should be at least 5 inches or 13 centimeters higher than the tallest flue. 

Step 1. The first thing you need to do is measure the width and the length from the top and bottom of all the flues. 

Step 2. Once everything is measured, measure the height of your biggest and tallest flue. 

Step 3. Now, measure the chimney top, its length, and width. 

Step. 4 After that, you can now choose one for your chimney flue. Remember to choose one a little bit taller than the tallest flue. 

Remember these things for a chimney cap size and stay on the right track when considering a cap for your chimney. See more related content in our article about the types of chimney caps on this page.