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Everything You Need to Know about Round Chimney Caps

December 18th, 2023 | 4 min. read

By Louis Greubel

A round stainless steel Draft King chimney cap installed on a mock chimney flue against a white background.

A chimney cap is a vital addition to any home with a fireplace. These protective covers help to keep rain out of your firebox and wildlife out of your chimney (and the rest of your home, too).

Chimney caps all basically fit into one of two categories: single-flue chimney caps that cover just one flue, and multi-flue chimney caps that cover two (or more) flues.

In the single-flue category, chimney caps can come in one of three shapes:

  • Square caps
  • Rectangular caps
  • Round caps

While there’s much to be said about each category and shape, in this guide, we’re going to focus on round chimney caps. At HY-C, we’ve manufactured tens of thousands of round chimney caps over the past few years, and we want to share what we know with you.

From the different types of round chimney caps to the materials they’re made from and the sizes they come in, there’s a lot to learn.

By the time you’re finished here, you’ll know which kind of round chimney cap is best for you, what material options you have, and what size you should get.

Round Chimney Cap Materials

A black galvanized round chimney cap next to a stainless steel round chimney cap of the same size against a white background

The best place to start when considering a round chimney cap is the material from which the cap is made. Different types of metal have different properties and work better in certain environments.

At HY-C, we make our round chimney caps from two types of steel:

  • Galvanized steel (with a black powder coat)
  • Stainless steel

In terms of price, black galvanized steel caps simply can’t be beat. They offer the best bang for your buck while providing an excellent level of protection. Their main drawback is that they’re susceptible to rust and corrosion in coastal environments due to high concentrations of saltwater.

On the other hand, stainless steel caps offer maximum protection and long term durability. They stand up exceptionally well against corrosion and can withstand weather and wildlife with ease. You’ll pay a higher price for this premium level of protection, though.

There is a third round chimney cap material to be aware of: copper. Copper caps are very expensive, but they’re also aesthetically appealing. We do offer round chimney caps in copper, but they’re rare. We produce them at a rate of less than one per year.

Round Chimney Cap Sizes

Thumbnail-style images of five different sized stainless steel round chimney caps (3 on the top row, two on the bottom) all against a white background

Not all round flue pipes are created equally. Different flues come in different sizes, and it’s important to find the correctly sized chimney cap for your flue.

We make the diameters of our round chimney caps in two-inch increments (eight inches, ten inches, twelve inches, etc.). Each size is designed to fit a flue pipe either one half-inch bigger or smaller than the size of the cap (i.e., an 8” cap will fit flue pipes from 7.5” to 8.5”).

The following table provides an overview of the round chimney cap sizes we manufacture and the flue diameter ranges they fit:

Cap Diameter Fits a Flue with a Diameter Between…
6 inches 5.5 inches to 6.5 inches
8 inches 7.5 inches to 8.5 inches
10 inches 9.5 inches to 10.5 inches
12 inches 11.5 inches to 12.5 inches
14 inches 13.5 inches to 14.5 inches
16 inches 15.5 inches to 16.5 inches
18 inches 17.5 inches to 18.5 inches

So, which size will you need?

It’s difficult to tell without measuring your chimney flue. What we can do, though, is offer some of the most popular sizes of round chimney caps we produce in terms of percentages:

Cap Diameter Percentage Manufactured by HY-C
10 inches 31.42%
12 inches 19.58%
14 inches 19.56%
8 inches 9.91%
16 inches 6.28%
6 inches 3.38%
18 inches 2.95%

The top seven sizes account for over 93% of the round chimney caps we make. The top three sizes — 10 inches, 12 inches, and 14 inches — account for over 70%.

If you have a round chimney flue, there’s a very good chance it will accommodate one of these three sizes. Even still, measuring your flue tile is still the best way to ensure you find the right cap size.

Round Chimney Cap Types

From left to right: a bolt-on round stainless steel chimney cap, a clamp-on round stainless steel chimney cap, and a slip-in round stainless steel chimney cap

After you’ve decided on a material and found the right size, one of the final things to consider about round chimney caps is which type to buy. “Type” essentially means “attachment style”, or the way the cap attaches to the flue pipe.

Round chimney caps come in three different types:

  • Bolt-on
  • Clamp-on
  • Slip-in

Bolt-on chimney caps are exactly what they sound like: they bolt onto the flue tile. We provide four bolts with all of our bolt-on chimney caps for ease of installation.

Clamp-on chimney caps come with a gear-drawn clamp around the base of the cap. To install one, you just slide the cap over the flue tile and tighten the clamp.

Slip-in chimney caps are perhaps the easiest to install. They come with four legs that slide into the flue tile. The legs bend under tension when inserted into the flue, and this tension holds them in place.

So, which type should you get?

Sometimes size determines which type you should (or even can) buy. Each type of cap comes in a different range of sizes. Make sure the type you’re interested in comes in a size that will fit your flue.

The other aspect to consider is how secure each attachment type is. Bolt-on caps are the most secure, while slip-in caps are the least secure. Clamp-on caps lie somewhere in between.

Should You Get a Round Chimney Cap?

You may not have realized just how much goes into choosing a round chimney cap. Sizes, materials, attachment types — there’s an endless number of combinations available, and finding the right cap for your flue can be overwhelming.

If you have a round chimney flue and it’s currently uncovered, we strongly encourage you to find a cap for it as quickly as possible. It will protect your fireplace from weather and storm damage and it will keep curious critters out of your home.

From there, it’s a matter of choosing the right material, finding the right size, and choosing the right attachment type. But even after all that is finished, you’ll need to install the cap on your flue once you buy it.

Our chimney cap installation guide covers seven different styles of chimney caps (including a few round caps). After you’ve found the right round chimney cap, use the installation guide to help finish the job.

Louis Greubel

Louis earned a bachelor's degree in English with a focus in rhetoric and composition from St. Louis University in 2017. He has worked in marketing as a content writer for over 5 years. Currently, he oversees the HY-C Learning Center, helping HY-C subject matter experts to share their decades of home solution products experience with homeowners and sales partners across the country.