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Why Do Basements Smell Musty?

Why Do Basements Smell Musty?

The minute you step into most basements, you might smell a musty, earthy aroma. Maybe it’s because of where basements are located in the house. But there is another reason basements often smell musty.

Basements usually have a musty smell because of fungus, water leaks, condensation on the windows, or unidentified water damage. 

Read on to learn more about why your basement might smell musty.

Is It Normal For the Basement to Smell Musty?

It is normal for basements to smell musty. The hydrostatic pressure from the soil surrounding the basement walls can cause the walls to crack.

Even the slightest crack can allow water from the soil to enter the basement.

Since most basements do not have windows or any other outlet, the moisture causes fungus to grow and causes it smell musty.

If your basement has a small window to help with the air circulation, the window might have condensation that causes a musty smell. However, the smell of fungal growth is quite distinct, and you can identify it because it smells like rotten eggs as soon as you step into the room.

Can a Basement Smell Musty Without Mold?

The basement can smell musty without the presence of mold and mildew. Wet or moist cardboards and carpets also cause a rise in humidity levels, causing the basement to smell musty.

The cause of the damage could be any water leaks. Since any moist surface provides a favorable place for mold growth, you should quickly identify the leak and the moist objects in the basement.

A lack of ventilation can also cause the basement to have a musty odor. Another contributing reason is the paint material and the furniture. If they emit certain VOCs, the air inside the basement can contribute to the mustiness in the environment.  

Here are some of the contributors to the musty smell in the basement:

Plumbing Leaks: Water leaks from HVAC units, drainage pipes, and pipe leaks cause a moisture buildup. When absorbed by furniture, wooden framing, carpets, or cardboard, the smell can increase from a moist smell to a strong musty one.

Washing Machine and Laundry Drainage: Many people tend to place and use washing machines in the basement. Because the machine uses water, it gets retained in the gasket, drainage pipes, and dryer vents. The bacterial and mold growth in these pipes, nooks, and crannies causes the air in the basement to smell musty, even if there is sufficient air ventilation.

Windows: If you live in an area where it rains a lot, the windows can have condensation buildup. This also causes a musty odor. If not treated, it may aid the growth of mold and mildew.

Dark dirty basement  with pipes

What Does a Musty Smell in the Basement Mean?

A musty smell in the basement is almost always associated with moisture and water. For example, if your HVAC vents have shown signs of condensation for a long, it means that the moisture in the ductwork has caused a growth of mold and mildew.

There might be other places where mold and mildew can grow. So, here is what a musty smell in the basement means:

Fungal Growth

A strong musty smell in the basement might mean that there is fungal growth in your basement. It could be either on the walls or on cardboard and wood stored in the basement that might have absorbed moisture.

The main reason that fungi find basements favorable for growth is that they are dark, warm, and do not have any air circulation. 

Also, the basement is surrounded by the earth from which the moisture of the soil finds its way into the basement walls.

If there is fungal growth in your basement walls, your basement will have a strong smell. Because as the fungus grows, the bad odor that emits from the micro-organism finds its way into upholstery, carpets, and curtains.

As a result, even a small level of fungi can get the entire basement to reek of an egg-like smell.


Moisture in the air because of washing machine usage and a damaged dryer vent can cause a musty smell.

The presence of water in the washing machine pipes and the dryer vents might cause mold and fungi growth inside too.

It goes undetected because this mold is not visible, but the smell grows as the mold grows.

How Do You Get Rid of the Smell?

There are many ways to get rid of the musty smell in a basement. It depends on the source of the smell in the basement.

So, first assessing the source of the smell is important before any remedies are implemented. Here are the ways to get rid of the musty smell:

Moisture from the Walls

If the moisture from the walls has found its way into the basement through cracks, you need to contact a basement waterproofing company.

The professionals can identify the groundwater entry points and seal them up. They might also install moisture control systems to regulate the moisture in the air.  

If you’re getting a house built, a foam insulation board and a protective wall covering make sure that the water does not find its way into the basement.

Also, wooden framing around the basement, when absorbs the moisture from the soil, might cause a musty smell. Again, rigid foam pieces can help stop the wooden frame from absorbing moisture from the earth.

Pipe Leaks

Plumbing leaks in the house structure can cause a moisture rise in the environment. Identifying the leak and getting it fixed is the solution to getting rid of the smell and making sure that the leak does not cause the growth of mold and mildew.

Pipe Leaks

Also, a damaged dryer pipe might be emitting moisture into the atmosphere. Therefore, you should get it fixed on a top priority before the concrete walls and furniture absorb the moisture and become host to fungal growth.

HVAC Ductwork Mold

Mold growth in the HVAC ductwork can also cause a musty smell. Because the basement is an enclosed space, if there is mold growth, you will probably detect it first in the basement.

But you might disregard it as a “normal” basement smell.

As soon as you get a musty smell in the house, you should immediately point to the ductwork and call for mold identification and removal professional services.

Summing Up Why Basements Smell Musty

Basements usually smell musty because of a lack of ventilation. The lack of airflow also causes a rise in humidity levels, which might cause a slightly musty smell first and then get stronger if the moisture causes mold and fungus to grow.

Several other causes cause fungal growth in the basement. The hydrostatic pressure in the basement walls might cause cracks which let in the moisture from the soil into the walls. 

This moisture is quite favorable to fungi and mold.

Pipe leaks, be it plumbing work or dryer vents are also a cause of moisture rise in the atmosphere. If the leaking water is absorbed by furniture or cardboard boxes, it causes an even greater chance for mold and fungal growth.

You can implement solutions based on the source of the issue. So, it is important to identify the issue first before you go for any remedies.

Lindsay Reed

Hi, I'm the founder of! I created this website to be a resource for everyone who wants to make the best home possible.