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Chimney Liners Buyer's Guide

Chimney Liners Buyer's Guide

If you own a traditional masonry fireplace or a fireplace insert, chances are you also have a chimney liner. However, if you are considering the purchase of a house with a chimney and have never owned one before, or potentially building one with no prior experience, you'll be asking yourself some questions. What are chimney liners? What are the costs involved? Do they require maintenance? These questions are important, and don't worry, getting to the end of this article will give you everything you need to know about a chimney liner kit and what it means to own one.

What is a Chimney Liner?

To be brief, a chimney liner is a metal or clay conduit that effectively lines the walls of a masonry chimney or older prefabricated chimney pipe. In a masonry chimney, the interior walls are usually made of brick, stone, or block. Modern chimneys are built with a clay liner affixed for the entire length of the interior. The clay liner consists of individual tiles that can be 8 to 24 inches tall. These clay liners can be damaged over time due to water intrusion from the top of the chimney or during the extremely high temperatures experienced during a chimney fire. Removal of the clay chimney liner with special tools will then be needed and a steel liner installed to allow the chimney to continue safe operation.

The Appeal of a Chimney Liner

A chimney liner is used in any instance where a new fireplace insert is being installed into an existing open fireplace. Gas fireplace inserts will use aluminum liners, while wood burning inserts require stainless steel. In addition to fireplace inserts, any open masonry fireplace that has an unlined chimney or a chimney with damaged clay flue tiles must also utilize a liner to correct the issue. The importance of having a chimney liner isn't up for debate. To be as safe as possible while using a wood fireplace or stove, a chimney liner is necessary because of the work that it does to draw the harmful gasses and combustion materials up and out through the chimney.

There are several indicators, some more subtle than others, that will proceed the need for a new chimney liner in a masonry chimney. When building a fire or cleaning out the fireplace after a fire, any small fragments of the clay flue tiles on the fireplace floor can be an indicator of a problem. The fragments will be a hardened material that is red or orange in color. This can indicate a badly cracked or deteriorating flue tile. Another indicator is poor operation of the chimney. Clay flue tiles can completely separate from the chimney walls and partially block the flue as they collapse. If you notice a sudden change in the behavior of your fireplace, cease using it at once and have the chimney inspected for any issues.

Deterioration of clay chimney liners is usually a relatively slow process, the only exception being the rapid damage that can result during a chimney fire. Regular inspections of the chimney flue will usually reveal any issues long before they become dangerous. A seasoned chimney sweep knows to look for cracking, scaling, or missing clay tiles. If any issues are revealed, it's time to remove the clay tiles from the chimney with a tile breaker and install a new steel liner. Removing the clay tiles ensures that enough space is made available to accommodate a new flexible chimney liner.

When equipping a fireplace with a fireplace insert, a chimney liner will also be utilized. Fireplace inserts require a chimney liner system that is sized to the appliance. The purpose of the liner in wood burning applications is to size the chimney down to the same size as the flue collar on the appliance. This ensures optimal performance and longevity. The manufacturer of the appliance will specify what size of liner should be used and what grade of stainless steel should be selected.

Direct vent and B vent inserts must also utilize a liner system. A type of dual liner kit called "co-linear" systems feature independent liners for combustion air and exhaust, which is required for direct vent applications. These liners are typically sold as complete kits that include a chimney cap and flashing. B vent inserts utilize combustion air from the room and as such, only need a single aluminum vent liner for the exhaust portion.

Before You Buy a Chimney Liner For an Open Fireplace

Chimney liners are sold in specific sizes, so knowing exactly which size you need is crucial so as to not waste time receiving the wrong size, or worse, attempting to install and use a chimney liner that doesn't fit. If a chimney is fitted with an improper chimney liner, it can result in poor performance and even damage to your appliance due to overheating. Luckily, this guide will give you everything you need to know to make the right decision the first time, so there is no confusion and wasted time.

There are a few steps to get the answers you need:

  • Precise measurements are required to know what size chimney liner you need. Follow the following instructions to get the correct information:
  • Measure the cross-section, both length, and width, of the chimney flue. If you are confused as to what to measure, the flue of a chimney is the space where the chimney starts, just above the fireplace opening. It is usually not possible to measure the chimney flue from inside the fireplace, due to the small access through the damper opening. The flue must be accessed from the exterior of the home. When taking the measurement, round up or down to the nearest inch. Also, remember to measure twice to ensure you get the same numbers. All of your numbers should be in inches, not feet and inches.
  • Next, you'll need to measure the fireplace opening in the same way you measured the chimney flue. Measure the height and width of the opening and mark down the best measurements you can get.
  • To get the final result, you'll have to do some math. The rule of thumb to guide you in this problem is to remember that ideally, a fireplace will have 10 square inches of opening for every 1 square inch of flue, or a 10:1 ratio. However, don't let this confuse you. Every fireplace is different, and you may have numbers that don't exactly coincide with that ratio, and there isn't a reason to panic if that happens.
  • Now, time for some math. Take the numbers from when you measured the chimney flue and multiply those two numbers. That final number is how large the opening of your chimney flue is in square inches.
  • Then, do the same with the numbers from when you measured the fireplace opening. The resulting number will tell you how large the opening is in square inches. Remember the 10:1 ratio rule? To understand how close your fireplace is to abiding by this rule, take the multiplied number from the length and width measurement of the fireplace opening and divide it by 10. This result will give you the ideal measurement of how large or small the flue should be in square inches. Compare that number with the actual measurement of the chimney flue.
  • Example — A fireplace opening measures 39 inches in width and 27 inches in height. This makes for 39 x 27 = 1,053 square inches. That being the case, we take 1,053 and divide by 10 to get a flue that should measure 105.3 square inches. 

When you get your measurements and if you find that your chimney flue isn't the ideal size, there is no reason to panic. It may be undersized, or it may have a larger opening than it needs, but as long as the fireplace works well, and it passes an inspection, it is perfectly fine. The above ratio is just a rule of thumb. However, if you find that your ventilation is less than adequate, and you see that your flue is undersized, additional work can be done to open up the flue enough to fix the problem.

Industry's Finest Chimney Liner Manufacturers


With 24 product lines and over 50 years of service, Duravent is one of the leading manufacturers of venting products. Duravent very likely has the product you're looking for. They make all kinds of chimney liners, but other products too, which can be very convenient for everyone needing to repair, replace, or build any type of fireplace. Their products are made to last, and with only the best materials available, you can be sure that you're getting a good product for the price. Their product lines cover stoves and fireplaces with all fuel types, including gas, wood, oil, pellet, and any other types. There are even a model of stainless steel chimney liner.


HomeSaver is a well-known manufacturer of quality chimney relining components, chimney caps, and insulation products. This company offers well-made stainless and galvanized chimney equipment in many styles. The products made by HomeSaver may be used with any type of stove or fireplace, as long as the product matches the type.

A Technical Breakdown of Chimney Liner Options

There are several types of chimney liners that cover all types of options, features, and applications. Most manufacturers will offer all types, but may only specialize in one or two, so be sure to study the product and its description before you purchase anything.

The common types of chimney liners are rigid or flexible liners, square liners, rectangular liners, oval liners, and round liners. There are also options in steel grade.

Liner Styles

Rigid Liners

Rigid liners are most appropriately used when resizing the chimney with a fireplace insert. 

A rigid chimney liner tends to be made with factory insulation between the inner and outer walls of the liner by most manufacturers. They are made to have a smooth surface on all sides. This is especially advantageous when sliding the liner into position, as the smooth surface helps to prevent binding or catching. The outer wall is also durable enough that any contact with the interior of the chimney will not cause damage.

Typically, rigid liners will come in sections that are up to 60 inches in length. Each end is manufactured to overlap by at least an inch and will be screwed together before dropping each section into position. Rigid liners require the use of a purpose-built top support system because of their overall weight.

Semi-rigid sections are pieces of the chimney liner that makes the connection between the fireplace insert vent collar and the first section of rigid liner possible. Most systems also offer offsets or elbows if there is a sudden change in the flue routing.

While more costly than flexible liners, the ease of installation and robust nature of these systems is enough for many customers to choose them. They can also be removed easily when it needs to be replaced or taken out to make way for other chimney repairs.

Flexible Liners

This type of chimney liner is generally the best option for relining jobs where the consumer is fairly sure that the inside of their chimney has offsets or turns in the flue. It is also the standard variety of liner that will be utilized for gas fireplace inserts.

While flexible liners are very easy to install and remove, they also have a corrugated interior surface which is more challenging to clean. However, there are purpose built brushes and chimney rod systems that aid in the procedures and ensure the flexible liner is safe to use.

A flexible liner intended for a wood burning application will almost never have insulation that comes with it, so you'll need to wrap the liner yourself. There are a couple of ways you can go about getting this part of the job done:

  • The first option is to use a ceramic wrap that encompasses the liner and is held in place with a mesh sleeve that is pulled over the wrap. The wrap option is ideal, but space will not always allow it, especially when using a square or rectangular liner that is just undersized for the flue.
  • The second option is to use pour in insulation. This type of insulation is a ceramic based granulated mix that is dampened and then poured from the top of the chimney between the liner and the flue walls. This type of insulation is more challenging to use because it requires a perfect seal at the bottom plate or the insulation will leak out and fall down into the fireplace. However, creating a tight seal is easy to achieve. You can also talk with the manufacturer of a product you have in mind to see if what they offer is sealed already. That feature may be what sets it apart from the others and may make shopping much easier.

Liner Shape

Round Liners — These are the most common chimney liners, being the most cost effective of the options.

Square and Rectangle Liners—Chimneys that are too small to afford the cross section you will use by installing a round liner may need a square or rectangular liner instead.

Oval Liners — A chimney liner of this shape can offer a good compromise between the cost of round and square/rectangular liners.

Types and Grades of Chimney Liners

There are several types of material that liners are made from:

430 Stainless Steel — This grade of stainless steel is usually found in low cost rigid chimney liners. It is only suited to wood burning or gas applications and should be cleaned often, as it offers only average corrosion resistance.

304 Stainless Steel — A step up in durability and corrosion resistance, this type of steel can handle high temperature wood burning applications, as well as gas applications. It is not recommended for use with flue oils or coal.

316 Stainless Steel — For applications that will be using coal, fuel oils, or high temperature wood burning fuels, 316 stainless offers enhanced corrosion resistance and fewer maintenance requirements.

316Ti Stainless Steel — Created by adding titanium to the stainless steel for a very durable alloy, this grade of steel is considered a "lifetime" product and can stand up to all fuel types.

3003 Aluminum — The standard for gas burning applications, the grade of aluminum features lightweight, but is also durable. It is the industry standard for both B-vent and direct vent liners.

Liners designed for sleeving a chimney are usually heavier, with a thickness of a approximately .018. The reason for this is due not only to the necessary corrosion resistance, but the greater possibility of liner puncture as it is being installed.

When to Replace a Chimney Liner

Relining a chimney for a fireplace insert can be quite the process but knowing when to tackle a relining job can save you money and time. Also, knowing when to reline your chimney is necessary for keeping your fireplace as safe as possible.

Exterior Chimneys — If the chimney flue tile area is 2 times the area of the flue collar on the appliance or less, then the chimney does not need to be relined.

Exterior chimneys are exposed to colder outdoor temperatures, which is why the tolerance measurements must be smaller compared to interior chimneys. This being the case, it is necessary to at least run a short section of flex liner from the appliance, up through the smoke chamber and just past the first clay flue tile. The smoke chamber is large and dissipates a great deal of heat, so bridging this short section ensures the appliance will operate as designed.

Interior Chimneys — If the chimney flue tile area is 3 times the area of the flue collar on the appliance or less, then the chimney does not need to be relined.

For open chimneys with a short section of liner, the ash and creosote will fall on top of the appliance, meaning that the appliance will need to be pulled out of the wall to clean the surrounding fireplace. The short section of liner will also need to be removed and taken outside to be cleaned. All of this extra work at cleaning time can make the one-time savings of not installing a full-length flue liner counterproductive.

Shipping Chimney Liners

Flexible liners, due to the sizes that they come in, tend to be shipped in a coil. This coil is then placed on a pallet and shipped via freight.

Inspect the pallet when it arrives, to make sure that the liner has arrived in good shape.

While this article may be a good bit of information, do not be discouraged to take on a project like installing or replacing a chimney liner for a fireplace insert. With the information here, you'll understand everything you need to know about how to get it done. However, ensure that you consult the manufacturer and the product guides that come with your hearth appliance.

About the Author

Collin Champagne

With over 13 years in the industry, Collin is a National Fireplace Institute (NFI) certified technician and managed content for the eFireplacestore and eCanopy brands. He has achieved the highest NFI certification possible as a Master Hearth Professional and is certified in all three hearth appliance fields: wood, gas, and pellet. With experience with sales and in-field installations, his expertise shines through his technical knowledge and way with words.

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