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What’s That Smell? Here’s Why You Have a Musty Crawl Space Smell

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Imagine sitting at home enjoying your evening only to notice a terrible odor filling the room and your nostrils.

If the pungent stench isn’t coming from your body or dinner, then have you checked your crawl space?

Your musty crawl space smell might be the reason you and your guests look for reasons to leave your house.

Here are some reasons and solutions for the odors.


Even though crawl spaces are small cramped places, different events and items can cause terrible smells quickly.

These are some of the main reasons:

  • Mold
  • Vermin
  • Soil
  • Forgotten storage
  • Dead animals
  • Sewage


While mold itself may not cause odors, any mold forming on wooden support beams or organic materials will build mildew and release smells.

You should know if you’re susceptible by going down into your crawl space and feeling if it’s damp.

Mold can also release mycotoxins that are extremely dangerous for your health. Finding mold or indicators of mold should be remedied immediately by a professional.


Cats, mice, rats, and insects can cause an insufferable stench.

Look for small holes or openings in the crawl space walls that would give access to rodents. A good test is to try and fit a pencil through any openings.

If a pencil can fit through a hole, then a mouse can, too.

The urine and droppings from vermin will permeate terrible smells throughout the crawl space. If you see one mouse or rat, you’re bound to see more if you let the problem go unchecked.


Believe it or not, soil can smell due to the organic material content. For homes that don’t have sealed floors, the exposed earth can produce a musty smell.

If the ground is moist, then anything organic in the soil will decay and release smells. Moisture always finds a way to the top, so it might be beneficial to have the crawl space sealed.

Make sure crawl spaces don’t use soil or earth from a rural farm. There’s good chance manure will be mixed in with the dirt.


Crawl spaces can become default storage areas for many homeowners. Trash, boxes of junk, and forgotten items are often left in crawl spaces.

Moisture will attach itself to anything and form mildew and mold.


Whether you’ve got cats or mice, a dead animal carcass will create a stinky situation.

Animals that make their home inside a crawl space tend to die in the same place. The decaying flesh from a snake or cat will fill your living room with an unbearable stink.

Do monthly checks and look for signs of animals and clear out nests.


A sewage leak or back up that spills into a crawl space will produce a terrible odor, but it will also introduce moisture under your home and be incredibly difficult to clean.

Protect your health by taking measures to avoid a sewage disaster. Sewage has toxins that can make you sick if inhaled.

These aren’t the only possible causes, but actively looking for these reasons may help you identify the source of awful smells.


Crawl spaces can provide up to half the air you breathe inside your home on the first floor.

Heat naturally rises, so when the air is displaced it is refilled by air that comes up from under the home.

Smells can also invade cracks, wiring, pipes, and joints in the floor to escape into the home. Once the smelly air mixes on the first floor, it can hit air ducts and continue traveling upwards to other levels.

If you discover mold in the crawl space, understand that you could be breathing mold particles into your lungs. This can create respiratory problems that last for life.


It might seem like a good idea to ventilate your crawl space, but the fresh air will actually cause more damage.

Warm air in the summer can build humidity below your home increasing the rate of rot or growing mold.

Cold air in the winter will cause your floors and overall house temperature to be lower than usual. Watch for high heating bills in this situation.

Older homes will naturally have vents in the walls of the crawl space. In the past, people thought vents would prevent foul smells from overwhelming the house.

The best thing to do to eliminate smells is to have a professional remove mold or soil with organic compounds, discard dead animals, and clear out any items that can deteriorate.

After foreign agents are removed, your goal should be to seal the crawl space and prevent outside air from reaching the area.


If your home has a crawl space and experiences these problems, consider getting the crawl space sealed or encapsulated.

The encapsulation will prevent moisture and humidity from building up under your home.

Be on the lookout for those who cut corners. Just putting a vapor barrier down on the floor of your crawl space won’t do enough.

If a company tries to tell you to install a dehumidifier without sealing vents, then it will run day and night costing you high energy bills.

Every opening to the outside should be sealed. All cracks should be covered by a plastic vapor barrier or permantently sealed. After this is completed, you can then install a dehumidifier to deal with any moisture that sneaks inside.

A dry and clean crawl space will be unappealing to insects, vermin, or other uninvited guests.


Don’t let your crawl space ruin your evenings and nose. Now you know what’s causing the odor, it’s time to fix the crawl space smell and save the structural integrity of the house at the same time.

If you’re ready to protect your home and health, then contact us today so we can start forming a plan for you.

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