How to Replace Furnace Flue Liner in a Masonry Chimney

A masonry chimney with a worn or damaged furnace flue liner poses a potential danger to the stability and functionality of a heating system within a home.

How Do I Know if My Chimney Liner Needs Replacing?

Chimney liners play a crucial role in ensuring the safety and efficiency of your fireplace. Over time, these liners can deteriorate and require replacement. One of the most telling signs that your chimney liner needs replacing is the presence of clay pieces or flakes in the hearth. These fragments are indications that the flue liner has broken down and is shedding into your fireplace.

Another red flag to look out for is excessive creosote buildup. If you notice a thick, tar-like substance accumulating on the walls of your chimney, it could be a sign that your liner is failing. A deteriorating liner allows creosote to stick to the brickwork, increasing the risk of a chimney fire.

In addition to visible debris, a faulty chimney liner can also lead to various performance issues. If you experience excessive smoke in your living space or notice a strong odor of smoke, this could be due to a compromised liner. The liners deteriorated condition may cause smoke to escape through gaps, potentially entering your home instead of exiting through the chimney.

If you notice a decrease in heat output or find it difficult to maintain a consistent fire, your liner might be to blame. A liner in poor condition fails to insulate properly, resulting in heat loss and an inefficient fireplace.

To determine if your chimney liner needs replacement, it’s recommended to consult a professional chimney sweep. They can perform a thorough inspection, assess the condition of your liner, and provide appropriate recommendations. Regular maintenance and timely liner replacement are essential to ensure the safe and effective operation of your fireplace.

How to Choose the Right Chimney Liner for Your Fireplace

When selecting a chimney liner for your fireplace, it’s essential to consider a few factors. Firstly, determine the fuel type used in your fireplace, as this will impact the liner needed. For instance, gas fireplaces typically require aluminum or stainless steel liners, while wood-burning fireplaces need more durable options like stainless steel or ceramic liners. Additionally, consider the size and shape of your chimney, as liners come in various dimensions. Lastly, it’s beneficial to consult a professional chimney technician who can assess your fireplace and recommend the appropriate liner based on your specific needs.

Cracked clay flue tiles can be a common issue for homeowners, resulting in the need for expensive repairs or even a full replacement. However, there’s now a cost-effective solution available: HeatShield®. This innovative chimney flue repair system offers an alternative to traditional methods by restoring clay flue liners instead of installing a new stainless-steel liner. So, if you’re experiencing cracked clay flue tiles, read on to discover how HeatShield® can be the right solution for you.

Can a Flue Liner Be Repaired?

Damaged or deteriorated mortar joints. The HeatShield® system works by applying a specially formulated “cerfractory” sealant to the interior walls of the flue, effectively restoring it’s integrity and improving it’s performance. This sealant is made up of a mixture of ceramic and refractory materials, which not only fills in cracks and gaps, but also resists high temperatures and corrosive byproducts of combustion.

The process begins with a thorough inspection of the flue to identify any areas of damage or weakness. Once identified, the flue is cleaned and prepared for the application of the HeatShield® sealant. The sealant is then applied using a specialized applicator, which ensures that it’s evenly distributed and adheres securely to the flue walls.

The advantages of using HeatShield® for flue liner repair are numerous. Not only does it provide an effective and affordable alternative to replacing the entire chimney liner, but it also extends the lifespan of the existing liner, saving you time and money in the long run. Additionally, HeatShield® can improve the overall safety and efficiency of your chimney system, reducing the risk of fires and improving draft performance.

This innovative solution offers a cost-effective and long-lasting alternative to replacing the entire chimney liner, allowing homeowners to restore the integrity of their flue without breaking the bank.

How to Choose the Right Professional for Flue Liner Repairs

  • Check for proper certification and licensing
  • Ask for references or read online reviews
  • Inquire about their experience and expertise in flue liner repairs
  • Get multiple quotes and compare prices
  • Ask about the specific materials and techniques they use for repairs
  • Ensure they offer warranty or guarantee for their work
  • Check if they’ve insurance coverage
  • Ask about the estimated timeline for the repairs
  • Inquire about any additional services they provide

Source: Questions to Ask Before Buying a Chimney Liner

When it comes to replacing a clay chimney liner, it’s important to consider the potential costs involved. On average, the expense can range from $2,500 to $7,000, depending on the extent of repairs needed. As an alternative to clay, many homeowners opt for a more durable option like a metal aluminum liner. This transition paragraph provides a brief overview of the cost considerations and the suggestion of a possible alternative.

Can You Replace Clay Chimney Liner?

If you’re in need of repairing or replacing your chimneys clay flue liner, you should be prepared for a significant investment. The average cost for this type of project can be around $2,500. However, it’s essential to bear in mind that if your chimney is in a severe state of disrepair, the costs can skyrocket to a range of $5,000 to $7,000.

In some cases, experts recommend replacing the clay flue liner with a more durable and cost-effective alternative: a metal aluminum liner. This option not only offers enhanced durability but can also alleviate some of the financial burden associated with constant repairs and replacements of clay liners. Metal aluminum liners tend to be more long-lasting and require less maintenance, making them an attractive choice for many homeowners.

Moreover, if your chimney is showing signs of significant wear and tear or has experienced extensive damage, replacing the clay liner becomes even more critical. Damaged flue liners can pose serious risks, such as leakage, gas exposure, and increased chances of fire hazards.

While the average cost of replacement can be substantial, investing in a metal aluminum liner can potentially save you from future repair expenses and offer peace of mind in terms of safety and effectiveness. Consulting with a professional in the field will ensure that you make an informed decision and secure the well-being of your chimney and home.

However, newer and more efficient furnaces, such as those with an AFUE rating of 80% or higher, do require a chimney liner for proper ventilation. This is because these furnaces produce cooler exhaust gases, which can lead to condensation and the buildup of harmful substances in the chimney. Installing a chimney liner helps to prevent these issues and ensures the safe and efficient operation of the furnace.

Do I Need a Chimney Liner for a Furnace?

These newer furnaces produce less heat, so the exhaust isn’t as hot. This can create condensation within the chimney, which can be problematic. The condensation can cause damage to the chimney, such as cracking or deterioration. It can also create a breeding ground for bacteria and mold.

Installing a chimney liner can help prevent these issues. A chimney liner is a protective barrier that’s placed inside the chimney. It helps to provide a smooth, insulated passage for the exhaust gases to exit the chimney.

There are different types of chimney liners available, such as stainless steel or aluminum. The type of liner you choose will depend on factors such as your budget and specific needs. Additionally, it’s important to have a professional assess your furnace and chimney to determine the appropriate size and type of liner needed.

Different Types of Chimney Liners and Their Advantages/Disadvantages

  • Clay tiles: long-lasting, affordable, but prone to cracking
  • Metal liners: durable, resistant to corrosion, but require professional installation
  • Cast-in-place liners: seamless, excellent insulation, but costly
  • Joint liners: easy installation, cost-effective, but may develop leaks over time
  • Insulated stainless steel liners: highly durable, excellent insulation, but expensive
  • Poured-in liners: seamless, resistant to heat and chemicals, but limited availability

When it comes to choosing the right type of mortar for clay flue liners, it’s important to opt for a medium-duty nonwater-soluble refractory mortar that meets ASTM C199 standards. This mortar should be used to create tight, smooth mortar joints on the inside of the flue liners. Additionally, it’s crucial to ensure that the flue liners are installed with enough airspace or insulation, without exceeding the thickness of the liners, to separate them from the interior face of the chimney.

What Kind of Mortar for Clay Flue Liner?

When it comes to choosing the right kind of mortar for clay flue liners, one must prioritize medium-duty nonwater-soluble refractory mortar that adheres to the standards set by ASTM C19This ensures the durability and longevity of the flue liner installation. It’s essential to use mortar that’s specifically designed for this purpose, as it needs to withstand high temperatures and protect against the corrosive effects of combustion byproducts.

To ensure proper installation, the mortar joints between the clay flue liners should be tight and smooth on the inside. This is crucial for creating a sealed and secure connection that prevents the escape of combustion gases. Careful attention to detail during the installation process will help minimize the risk of chimney leaks and ensure optimal performance.

Equally important is maintaining an airspace or insulation between the flue liners and the interior face of the chimney. This airspace or insulation shouldn’t exceed the thickness of the flue liner.

Investing in a medium-duty refractory mortar that meets industry standards guarantees a secure and long-lasting installation. The tight and smooth mortar joints, along with the proper insulation or airspace, further enhance the performance and longevity of the flue liner, ensuring the efficient expulsion of combustion gases and safeguarding against potential chimney damage.

Comparing Different Types of Mortar for Clay Flue Liners

When it comes to comparing different types of mortar for clay flue liners, it’s essential to consider various factors such as their composition, strength, and stability. Mortar serves as the binding material between clay flue liners, ensuring a secure and durable installation. It’s important to select a mortar that’s compatible with clay flue liners and can withstand the high temperatures and corrosive gases produced by a fireplace or chimney. Comparisons can be made based on factors like heat resistance, adhesive properties, and resistance to creosote buildup. Ultimately, it’s crucial to choose a mortar that provides a reliable and long-lasting bond for clay flue liners to maintain the safety and efficiency of the chimney system.


In conclusion, replacing a furnace flue liner in a masonry chimney is a complex task that requires careful planning and execution. It’s essential to prioritize safety and adhere to building codes and regulations to ensure an efficient and effective replacement. By thoroughly assessing the chimney's condition, selecting the appropriate liner material, and following proper installation techniques, homeowners can restore their chimney's functionality and prevent any potential hazards. Additionally, seeking professional guidance and assistance can provide valuable expertise and ensure a successful outcome. Ultimately, with the right approach and attention to detail, the replacement of a furnace flue liner can be accomplished smoothly, allowing for continued safe and reliable operation of the heating system.

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