Fireplace Mold: 7 Common Causes And Solutions (Easy Methods)

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Worried about fireplace mold? This article outlines the most common causes of fireplace mold and what you can do to prevent it.

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One of the most common problems homeowners face is mold growth in the chimney and fireplace.

Chimneys and fireplaces are typically located in humid areas of the house.

When combined with the heat from the fire, this creates the perfect environment for mold to thrive. If your fireplace or chimney isn’t properly maintained, it can become a breeding ground for mold.

Let’s discuss the main causes of fireplace mold and proven ways to eliminate fungi.

Can mold grow in a fireplace?

Mold can grow inside the fireplace. The fungi often thrive in damp areas and can be found in hard to spot areas of chimneys and fireplaces.

Part of diagnosing fireplace issues involves identifying and addressing these less obvious problems like mold growth. Sealing water leaks and fixing damaged components of the chimney can prevent further mold growth.

7 Common reasons for mold in fireplace

Here are the common causes of fireplace mold:

1. Lack of ventilation

Ventilation needs to be good for your chimney to function properly.

Some things that make your chimney not vent properly include debris in the chimney such as leaves and broken flue tiles.

The accumulation of these elements blocks the condensation created during the burning of firewood. This creates moisture in the fireplace and encourages the growth of mold.

2. Cracked chimney crown

The chimney crown is a concrete slab at the top of the chimney masonry whose function is to prevent water from coming in through the chimney.

If it is cracked, it will allow water to enter your chimney. This will increase the amount of moisture in the fireplace and promote mold growth.

3. Masonry damage

The chimney masonry is usually durable and will protect your chimney for many years.

However, the brick and mortar will deteriorate with time due to exposure to elements like snow, rain, winds, and ice.

An obvious sign of masonry damage is spalling bricks caused by the freezing and thawing of water in the bricks.


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4. Damaged or loose chimney cap

The chimney cap can also let in water through the chimney if it is loose. The chimney cap can be damaged by rust, extreme weather, and holes caused by fallen branches.

Another thing that can allow water leaks into the chimney is the wrong cap size and improper installation.

5. Moisture

If water is leaking through your chimney, you will start noticing signs of mold growth. 

One of the main signs of mold growth in the fireplace is a musty smell.

Some common reasons for water leaks in the chimney include:

  • Damaged chimney crown and cap
  • Blocked chimney
  • Damaged masonry

6. Chimney water leakage

Water leaks contribute a lot to the growth of black mold in the chimney fireplace. When it rains, water can leak through a damaged chimney flashing, a critical issue that needs addressing.

Additionally, smoke chamber parging is another important maintenance aspect that should not be overlooked. Parging the smoke chamber can help prevent deterioration caused by moisture and improve the overall functionality of the chimney.

Flashing is the waterproof sealant that protects the chimney from water leaks. It is typically found at the junction of the chimney and the roof and is made of materials like aluminum and steel. Regular inspection and maintenance, including flashing repairs and smoke chamber parging, are essential to prevent leaks and mold growth.

Watch out for signs of chimney flashing damage like rust stains and dripping sounds. If you suspect that your flashing is faulty or if you need smoke chamber parging, contact a certified chimney sweep to address these issues promptly.

7. Damaged or loose chase cover

In prefabricated chimneys, the chimney chase cover is an important compone

nt that prevents water, debris, and animals from entering the chimney.

If it is loose or broken, it lets in water through the chimney and creates a moisture-rich environment in the fireplace leading to mold growth.

Chase covers can be damaged by rust, lightning strikes, and hail storms. A professional will help you find the right replacement for your damaged chase cover.

Risks associated with mold growth in a chimney or fireplace

  • Health Problems – Mold growth in the fireplace causes allergic reactions like sneezing, runny nose, wheezing, coughing, fatigue, headache, and watery eyes. The most affected are the children, people with underlying respiratory problems like asthma, and the elderly with weakened immune systems.
  • Musty smell – Mold growth in the fireplace causes a musty odor that triggers allergic reactions such as an itchy throat and runny nose.
  • Moisture damage – Excessive moisture can wreak havoc in your home. First, an increase in moisture means the growth and spread of mold in your house. Note that mold can damage other items in your house such as furniture. Moisture can also cause stains on your walls and ceiling.

Evidently, excessive moisture in your home is dangerous. If you don’t take action early, you will spend hundreds or even thousands of dollars on repairs.

Contacting a professional chimney sweep when you notice fireplace mold growth is vital.


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How to get rid of mold in fireplace?

There are two ways to get rid of mold in your fireplace. The first is a DIY method. Keep in mind that mold removal can cause serious complications if you don’t take the necessary precautions.

For instance, you shouldn’t try to remove mold if you don’t have the right equipment and protective gear, such as gloves, long pants, and waterproof boots.

Here are the steps to removing mold in the fireplace:

Step 1: Buy an antifungal cleanser.

Step 2: Use a flashlight to check the fireplace for mold growth.

Step 3: Use a hard brush to clean the mold. We recommend using a long brush to reach all parts of your fireplace.

Remember, you could damage your chimney or put your health at risk when removing the mold.

It is safer to get a professional chimney sweeper to eliminate the mold. A chimney sweep will first inspect your chimney to see what’s causing fireplace molds.

It could be anything from a damaged chimney cap to the build-up of debris in the chimney flue. They will then help you get rid of the mold and recommend ways to prevent fireplace molding.

Tip to prevent mold growth inside chimney and fireplace

  • Annual fireplace Inspection and cleaning – This ensures all your chimney’s components are functioning well.
    Not inspecting your chimney annually can worsen damages and significantly increase repair fees.
  • Waterproofing – If the chimney masonry starts to deteriorate, water will start leaking and increase the moisture in your chimney.

If this happens, add mortar using a caulking gun and then replace badly damaged bricks. The final step is to waterproof the masonry with waterproofing to prevent future leaks.

If the leak is in the chimney flashing, apply a new sealant. Ensure you do this during warm weather so the sealant dries quickly.

A professional chimney sweep should do waterproofing as they are more experienced and will use the right products.

  • Install or replace broken Chimney cap – Make sure you have the right chimney cap or chase cover size. Also, the installation should be done by a chimney sweep.
  • Make sure your indoor humidity is between 30% and 50% – This ensures the moisture levels are not high and discourages fireplace mold growth.

Fixing water leaks in the chimney and other parts of your house should do the trick.

Final thoughts

Fireplace mold is a problem that many homeowners face. Apply the above solutions to prevent fireplace mold. A surefire way to prevent mold growth in your chimney is to schedule annual chimney sweep inspections.


Can mold start a fire?

Mold cannot start a fire. Water leaking through the chimney will cause condensation in the chimney flue leading to chimney mold and creosote formation. Creosote burns easily and can cause dangerous chimney fires or in extreme cases, house fires.

Does fire kill mold spores?

Fire can kill various types of mold. Mold can be destroyed when exposed to high temperatures (from about 160 degrees Fahrenheit) for a long. However, you shouldn’t burn mold as they release spores that can trigger allergic reactions like a wheezing and runny nose.

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Thomas Green

Thomas has worked in the Chimney & Fireplace field for over 12 years. He is an expert in his trade and loves to help People with their needs. Thomas Write helpful articles so that homeowners can make the most informed decisions about their fireplace and chimney.