Can Mold Grow Inside My Fireplace or Chimney?


The experts at My Pure Environment know that mold can grow almost anywhere—even inside your fireplace or chimney! Mold can grow wherever it finds warmth, darkness, and humidity. Fireplaces that don’t get used very often—especially those that sit idle for several months in hot and humid climates—can be the perfect breeding ground for mold.


How Can Moisture Get Inside My Fireplace?

If there’s moisture inside your fireplace or chimney you could have mold. Damp can creep into your masonry in many different ways. Here are a few things to check for:


1: Cracked Chimney Crown

The chimney crown, or chimney wash, is a large slab of concrete, metal, or stone that covers the top opening of the chimney and protects it from rain and ice. If the crown is cracked or chipped, water can seep in between the flue and the chimney exterior and create a moisture-rich environment.


2: Broken Chimney Cap

Similar to a broken chimney crown, if the cap on your chimney is damaged from severe weather, improper installation, or rust, water can seep into your chimney and fireplace. If you do not have a chimney cap, get one! Make sure to install a cap with joints that allow for expansion and contraction with temperature changes, so you can keep your chimney dry.


3: Missing or Damaged Chimney Flashing

You should have vinyl, aluminum, copper, or steel flashing installed where your chimney meets your roof. If the chimney flashing fails, it can lead to water seepage and leaks. In addition to causing serious damage to your roof and attic, damaged flashing can allow water damage that causes mold to grow.


4: Poor Air Ventilation

If you don’t have sufficient air ventilation, you could have moisture and condensation trapped in your chimney. Check your ventilation to ensure that air can circulate and keep your chimney dry, in order to prevent mold growth.


5: Non-Waterproofed Brick and Mortar

Chimney masonry can last a long time, but the mortar that holds it all together does not. If the mortar of your chimney wasn’t properly sealed, it could crack and crumble, allowing moisture to get into the masonry.


How Do I Know If I Have Mold Growing in My Chimney?

In some cases, you might be able to see black mold spots or fuzzy white mold spores clumped together on the bricks in your fireplace. However, mold often thrives deep inside the chimney, where it’s harder to see. One sure sign of mold is a pungent, musty odor. Give your fireplace a sniff, and if it smells musty, you could have mold growing inside. This is even true if your gas fireplace smells musty.


How Can I Prevent Mold in My Fireplace?

The best way to prevent mold in your fireplace is to make regular inspections of your chimney, chimney crown, and chimney cap. Make sure there are no leaks or sources of moisture inside your fireplace. Always waterproof your chimney and seal your fireplace masonry. Remember, without moisture, mold cannot grow.


Protect Your Home from Mold

If you suspect that you have mold growing inside your fireplace or chimney, contact My Pure Environment today. Our patented two-step mold remediation process penetrates deep into places where mold spores can settle, and eradicates them on contact. Then, we treat the surfaces of your home to ensure that the mold stays gone for up to 90 days. Contact us to schedule your onsite air consultation today.



Photo by Erik Mclean on Unsplash used with permission under the Creative Commons license for commercial use 12/15/2021.



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