5+ Dangers of a Cracked Flue + Fixes

  • The flue is the part of the fireplace that will regulate temperature and will keep harmful gases out of the home.
  • Cracks in the flue can be dangerous. They may let harmful gases into the home and will compromise the structure of the fireplace.
  • Flue repair is needed so that the fireplace can work effectively and will operate safely.

For a fireplace to be working properly and safely all parts must be in good condition and nothing should be damaged. The chimney flue is an important part of the system. The flue should be inspected annually to make sure it is in good working condition.

If the chimney flue is cracked it can be dangerous and there will be some safety issues with having a fire. If the chimney flue is cracked then a person should not use the fireplace. This is true even if there is a small crack in the flue.

There are many reasons why it is dangerous to have a fire in a fireplace with a cracked flue and a person should not do this.


  • Functions of the flue
  • Dangers of cracks
  • Why repair is needed

Purpose of the Flue

Purpose of the Flue

The purpose of this flue was to be safe. Before 1940, chimneys were not built with a liner or with any similar type of protection. Over time it was discovered how dangerous this was a changed were made.

there are liners and chimney flues to increase safety and for additional protection

Heat Protection

The flue and the chimney are important for heat management. According to information from the National Bureau of Standards fireplaces that has a crack in the flue could catch fire in as little as 3 hours of use.

The use of this flue is to help prevent the flammable and combustible parts of the home from being exposed to these hot temperatures. If parts of the home are exposed there can be a major issue and fire hazard.

When the flue begins to show signs of deterioration or cracking it needs to be repaired or replaced.



When it comes to the chimney the flue will act as a protectant. Acidic material and gases may be built up and they may damage the bricks and the mortars in the structure.

Mortar erodes very quickly and it can allow moisture into the home leading to even bigger problems if there is an issue with this flue the entire chimney may collapse and need to be replaced.

Protection from Toxins

Hazardous gases can get into the home and this can lead to a lot of trouble. No one wants to be poisoned due to their fireplace. Even the smallest crack in the flue can lead to issues. Toxic fumes such as carbon monoxide can get into the home.

This gas is odorless and colorless. No one will know that it is there until it is too late. The flue should be inspected yearly to make sure there are no cracks and no way for these gases to get into the home.

As a backup, a person should also have a carbon monoxide detector to warn them of any potential danger. Toxins are not something to mess around with and all precautions needed to be taken to ensure that the family is safe from any danger.

Types of Flues and Flue Liners

Over the years there have been advances in chimneys and homes have been built safer. A person should still be aware of the type of material their chimney is made out of so they can look out for potential dangers.

Clay Tile

Clay Tile

This was the most common type of flue for homes in the United States. Clay tile does a good job of protecting a home and it is inexpensive. This material will also last around 25 years before it needs to be replaced.

At this time a person should still look at the flue and make sure it is in good condition. Like most materials tile will wear down over time and crack. It may need to be rebuilt. If a person has a fireplace with cracked tile in the flue they should not use it as this will be dangerous.



Most flues and their liners are made from a stainless steel material. This is newer and it does not require a complete replacement. These liners have been approved by the Chimney Safety Institute of America as long as they have proper installation.



If there is a crack in the flue it will not be running up to its potential. Modern flues will help keep the home warm and they will make sure no gases get into the home. The purpose of the fireplace is to keep the home warm and if there is an issue with the flue the home will not be able to be as warm as it should be.

The flue should be around an inch wide for every 10 square inches that account for the fireplace opening. This will allow for proper airflow and it will allow the home to be heated properly. If the flue is not the correct size or has cracks or holes will reduce the efficiency.

If the flue was built too small the smoke will not be able to escape fast and this will lead to smoke in the home.

How to tell if the Flue is cracked

Most people do not know if their flue is cracked. There may be no signs until it is too late. The best way to have the fireplace looked at is to have an annual inspection. This should be done to make sure the fireplace is in good condition and there is nothing more.

A person should contact a professional chimney repair service to make sure there are no cracks. If there is an issue with the flue the repair person may be able to replace the liners.

The professional should be highly trained and certified to make sure they are doing a quality project and to make sure they repair the flue for the safety of the family.

these are some of the dangers of having a fireplace flue that is cracked and in need of repair. A cracked flue can put the family at risk for many conditions. An annual inspection of the flue can make sure that it is safe and that a family can enjoy a nice fire without having to worry.

Eugene Duke Pic

Hi, my name’s Eugene Duke and I love sitting by my fireplace reading a book and sipping on an adult beverage. Do you have a fireplace in your house? I’ll help you figure out the best type and style of fireplace for your home.


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