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Feb 8, 2023

11 minutes

Musty Smells In Crawl Space – Causes And Removal

Earthy and musty smells in your crawl space can be an unsettling sign of a problem. Poorly ventilated and unclean spaces like these could indicate the presence of mold, mildew, moisture buildup, and even pests. Not only are these smells unpleasant, but they can also be hazardous to your health.

Addressing the problem source and removing crawl space odors is essential in preserving your home and health. From identifying the source of the smell to implementing solutions, this article will guide you through getting rid of crawl space smells and improving air quality. Let’s get started.

Causes Of Crawl Space Smell

Several common things can cause a musty smell in your crawl spaces. The most likely culprits are:

1. Moisture

Inadequate ventilation in a crawl space can lead to moisture buildup, creating a damp environment that encourages mold growth and causes musty odors. Humidity from the outdoors can also creep into a poorly insulated crawl space, causing moisture and musty odors. Also, plumbing and drain pipes can leak, causing moisture buildup and leading to musty odors.

2. Mold

Mold is a common source of musty odors in crawl spaces. If you have any moisture or water leaking into the area, mold can quickly take over and cause an unpleasant smell. Also, if there is a lot of clutter or debris in the crawl space, mold can grow and cause a musty smell.

3. Rodents

Rodents are attracted to dark, moist spaces like basements and crawl spaces as they provide shelter from predators. They can also quickly create a mess and leave behind droppings that create unpleasant odors. The presence of rodents in a crawl space can also lead to more moisture buildup, which contributes to musty smells.

4. Poor Drainage

If your crawl space does not have proper drainage, water can collect in the area and lead to musty odors. Improperly graded soil around the foundation can also cause surface runoff from rain or snowmelt to seep into the crawl space and create a damp environment.

5. Poor Insulation

Insulating your crawl space is essential to keeping out moisture and preventing a musty smell. If your insulation has become worn or damaged, it can allow moisture from the outdoors to penetrate the walls, leading to mold growth and bad smell.

6. Air Leaks

The gaps, cracks, and holes in your crawl space can also be one of the causes of a musty smell. Leaky air ducts can provide a place for moisture to enter the space, leading to mold growth. Also, the leaks can allow odors to escape and spread throughout your home.

7. The Stack Effect

The air you breathe is up to 40% of your home’s crawl space. Warm air naturally moves upwards through the “stack effect,” like a smoke stack. This happens as air passes through gaps and crevices in floors and walls created during construction by plumbers, electricians, and HVAC contractors for purposes such as running pipes and wires or installing air ducts. Changes in building materials also cause openings, leading to further air movement. Warm air rises, carrying odors, and the musty smell can escape into your home.

8. Sewer Gas

Sewer gas combines gases produced by microorganisms found in the sewage system. It can enter your crawl space if there is a plumbing leak, corroded pipes, or poor connections. The smell of sewer gas will be easily noticed and typically indicates that some repairs need to be made.

9. Standing Water

Standing water can be a major issue for crawl spaces with inadequate drainage and create a musty smell. The presence of water can cause mold growth and encourage the growth of mosquitoes, which is another potential source of bad smells.

10. Organic Residue

Organic residue can accumulate in crawl spaces due to high humidity or inadequate ventilation. Organic residues are often the result of plants, food, and other organic materials being left behind in the crawl space area. This can lead to a musty smell that is difficult to ignore.

Crawl Space Light Fixtures

Steps To Eliminate Odors In Crawl Spaces

To get rid of musty odors in your crawl space and make it a healthier place to live, use the following steps:

1. Inspect Your Crawl Space

Start by inspecting the area for any signs of water damage or mold growth causing the smell. Check for standing water, warped wood, and any other indications that moisture is present. The odor source could be something as simple as a wet rug, so look for anything out of place. Also, inspect for vents that could be drawing outside air in, as this may contribute to the musty scent.

2. Clean The Area

Once you’ve identified any areas of concern, you can begin to clean the crawl space. Start by removing debris and clutter from the area. Any damp items should be removed as well. Next, vacuum the area with a HEPA-filtered vacuum cleaner to remove dust and dirt buildup that could contribute to the odor. Also, be sure to clean any exhaust vents and air filters.

3. Repair Any Rot-Damaged Wood

If you’ve noticed any rot-damaged wood, it’s important to take steps to repair the damage. This may include replacing boards or sealing the affected area with a moisture barrier. Also, ensure that any gutters and downspouts are in good condition to prevent water from seeping into the crawl space.

4. Seal All Vents And Install An Airtight Door

Crawl space air must be sealed off from the outside. This can be accomplished by sealing vents with a moisture barrier, such as caulk or plastic sheeting. Ensure all gaps and cracks are sealed to prevent outside air from entering the space. An airtight door should also be installed to help keep the area free of odors.

5. Install A Dehumidifier

Consider installing a dehumidifier to reduce humidity levels in your crawl space further. This device sucks moisture from the air and helps to reduce mold growth, which could be contributing to musty odors. Also, you can use fans to help circulate the air in the space and prevent odors from lingering.

6. Deal With Fungus And Mold

You may need to deal with any fungus or mold growth in the area for severe odors. This can be done by using a fungicide or cleaning the area with a bleach solution. If mold is present, it should be completely removed and replaced before attempting to cover up the odor with a deodorizer. Also, repair any water damage to prevent future mold growth. Utilize a moisture barrier to keep the area dry.

7. Install A Crawl Space Barrier

Consider installing a vapor barrier if your crawl space has chronic moisture issues. This heavy plastic sheeting covers the floor and walls of the space to create an airtight seal that keeps out moisture and odors. Also, be sure to remove any old insulation or debris that could be contributing to the smell.

8. Waterproofing System

You may need to consider a waterproofing system for more serious water issues. This involves installing a sump pump and drainage system that removes any standing water and prevents future flooding. It also helps to reduce humidity levels and prevent mold growth in the space. Also, ensure that gutters and downspouts are in good condition to prevent water from seeping into the crawl space.

9. Use All-Natural Deodorizers

To further mask musty odors, consider using all-natural deodorizers such as baking soda or essential oils. Sprinkle baking soda on affected areas and leave it overnight before vacuuming. You can also use a few drops of essential oils on cotton balls and place them around the area. Both methods help absorb odors and leave a pleasant scent behind.

10. Call In A Professional

If you still have musty odors in your crawl space, it may be best to call in a professional. They can inspect the area and recommend the best action to eliminate the odor. Don’t hesitate to contact a professional if you need help removing that smell in your crawl space.

Crawl spaces tend to affect the fresh air quality of the living space

Prevent Crawl Space Smells In The Future

Once you have removed the musty odor from your crawl space, there are several steps you can take to reduce the chance of unwanted smells in the future.

  • Regular Cleaning: Keeping your crawl space clean and dry is essential. Have it professionally inspected and cleaned every year. This will help to prevent the buildup of dust, dirt, mold, and other odor-causing substances that can accumulate in the area.
  • Control Moisture Levels: Humidity is the main cause of musty smells in crawl spaces. Install a dehumidifier to reduce the moisture content and discourage mold growth. Make sure your crawl space is also well-ventilated with air circulation.
  • Check For Leaks: If you notice any water damage or leaks, repair them immediately. Check all pipes, HVAC systems, and roofing for any signs of corrosion or water damage. If you suspect a more serious problem, call in a professional to take a look.
  • Sump Pump: Consider installing a sump pump if you have a damp crawl space. This will help reduce the amount of groundwater and moisture that accumulates in the area, reducing the chances of musty smells.

Create A Healthy Crawl Space Environment

You can create a healthier home environment by dealing with the musty smell in your crawl space. Taking the right steps to remove and prevent moisture and mold growth will help keep your home safe and clean.

Healthy airflow is key to keeping your home environment free of excess moisture. To do this, consider installing vents or fans around the crawl space to promote better airflow. Be sure to seal up any gaps in the wall, too, so that no additional moisture is getting into your home. Once you have improved air circulation, install a dehumidifier to help reduce humidity and prevent musty smells from accumulating, and enjoy the fresh air.


1. Is It Normal To Have Smell In The Crawl Space?

No, it is not normal to have a smell in the crawl space. High levels of moisture or mold growth could cause it. If you notice any dampness or mustiness in your crawl space, it’s best to investigate further to determine the source of the issue.

2. Can I Handle The Smell In My Crawl Space On My Own?

It’s possible to address the smell in your crawl space with some DIY efforts. For example, if you suspect the smell is from mold or mildew, you can use an anti-fungal cleaner to help eliminate it. You should also ensure that your crawl space is properly ventilated and, if necessary, install a dehumidifier to reduce moisture levels. However, if the cause of the musty smell is mold growth or high moisture levels, it is highly recommended to call a professional for assistance.

3. What Are The Long-Term Effects Of Smell In The Crawl Space?

A musty smell in the crawl space can signify excess moisture or mold growth, leading to serious health problems. In high concentrations, mold spores can cause respiratory illnesses, headaches, and other allergic reactions. Additionally, dampness can cause damage to your home’s structure and create an environment conducive to the growth of pests and other insects.


Eliminating musty smells in a crawl space can be complicated, and it is important to identify the source before attempting removal. While mechanical ventilation and dehumidification systems are effective solutions, they can be costly. The best plan of attack is first to address any moisture issues, then use appropriate methods like sealing cracks in the foundation and replacing insulation. Cleaning out debris regularly and ensuring proper air ventilation can also help to minimize the musty smell in a crawl space. You can have a clean and odor-free crawl space with the right approach for years.

Crawl Space Insider
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