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Solve the Mystery Lurking in Your Basement or Crawl Space

Decomposing dead mouse in a crawl space

Dead rodents, mold, radon, water, and dust mites are just a few of the problems found in basements and crawl spaces.

The air is musty, the floor is cold and damp, there are creepy-crawly bugs, and ugly stains on the wall. It sounds like a scene from a scary movie, but what we're describing is a typical basement. If your basement is unfinished, it's probably not a space where you want to spend a lot of time. And if you have a crawl space, you probably don't spend any time in there unless there's a problem, like a plumbing leak.

Even if you don't plan to use your basement as living space or your crawl space for storage, hazards lurking in your basement or crawl space can spread to other parts of your home. Here, we'll uncover 10 common problems lurking in the basement or crawl space, what to look for, and resources to help with fixing each problem.

  1. Mold

    Mold is common in basements and crawl spaces, especially when there's too much moisture. A leaky foundation or condensation from appliances could be to blame.

    Moldy drywall in the basement

    What to look for: A musty smell in the basement or crawl space probably means there's a mold problem. Mold growth can usually be seen in areas where there are leaks or water damage. Mold can grow on any item or building material made from organic substances, such as drywall, wood, carpet, insulation, wallpaper, furniture, cardboard boxes, and clothing. Mold spores can cause health issues, such as runny nose, sneezing, coughing, watery eyes, and itchy skin.

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  2. Water

    Wet basements or crawl spaces can be caused by flooding, water seepage through cracks in the foundation, leaky window wells, a plumbing leak, or a burst pipe.

    Puddle of water on a crawl space floor

    What to look for: Standing water, or puddles in your basement or crawl space is obvious, but other symptoms of a water problem can be harder to spot. Condensation, mold, mildew, efflorescence (white, chalky stains), wet drywall, wet carpet, bowing walls, and musty smells are indicators of water leaks and high humidity.

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  3. Radon

    Radon gas is present in soil, rocks, and in the air you breathe every day. Radon can come up through the ground and through cracks in the foundation into the home. Radon exposure can happen no matter what type of foundation you have, whether it's a basement, crawl space, or slab.

    What to look for: You can't see, smell, or taste radon. The highest concentration of radon tends to be found in the basement or on the first floor. Exposure to radon can damage cells in your lungs, which can lead to lung cancer. The only way to know for sure if you have too much radon in your home is to test for it. A radon level of 4 picoCuries per liter (pCi/L) or more is considered high and should be reduced.

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  4. Carbon Monoxide

    Carbon monoxide (CO) is found in the fumes when fuel is burned. CO is a concern in basements with a fuel-burning furnace, stove, fireplace, or gas range. The invisible gas can seep into your living space, creating a risk of health symptoms, fire, and possibly death.

    What to look for: CO is colorless and odorless, but it can build up indoors and lead to CO poisoning in people and animals. The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion.

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  5. Pests

    Many bugs and other pests are attracted to damp, dark spaces such as basements and crawl spaces. Common pests found in these areas include silverfish, pill bugs, cockroaches, mice, rats, and carpenter ants.

    What to look for: If there's a strange smell coming from your air vents, you might want to check for a dead critter in the basement or crawl space. Dead animals or pests can cause a foul odor in the basement or crawl space and upstairs. Droppings and holes in fabric and clothing are also common signs of pest activity in the basement or crawl space.

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  6. Wood Rot/Dry Rot

    Rotting is a common problem in basements and crawl spaces because of water problems and high humidity.

    Rotted wood along the basement floor

    What to look for: Bouncy, creaky floors aren't just a problem in old homes or haunted houses. Bouncy and sagging floors over the basement or crawl space is a symptom of wood rot, but can also be caused by undersized floor joists or support beams, settling support posts, or insect damage.

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  7. Dust Mites

    Warm, humid basements (finished and unfinished) are the ideal environment for dust mites. Dust mites are microscopic organisms that feed on our dead skin cells in the dust in our homes.

    What to look for: You can't see dust mites, but their waste can cause an allergic reaction and make asthma symptoms worse. Symptoms of a dust mite allergy include sneezing, runny nose, itchy nose, and nasal congestion. Reducing the humidity in the basement can help with controlling dust mites.

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  8. Condensation

    When humid air comes in contact with a cold surface, it condenses and forms droplets of water, or condensation.

    Condensation dripping from sweating pipes in the basement

    What to look for: Humidity plus cold temperatures and surfaces in the basement or crawl space creates condensation on metal pipes, ductwork, concrete floors, and walls. Condensation can lead to mold and rust on objects and surfaces in the basement.

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  9. Efflorescence

    Efflorescence is dissolved salt deposits on the surface of a porous material, such as concrete or brick, after water has evaporated.

    Efflorescence on concrete basement walls

    What to look for: Many people mistake the white, chalk-like stains on the basement walls and floor as mold. These stains are actually efflorescence. Efflorescence is usually a sign of a leaky basement.

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  10. Open Sump Pit

    The sump pump is the hole in the basement floor that houses the sump pump. When water collects inside the pit, the sump pump kicks on and pumps the water out of the house to prevent flooding.

    An uncovered sump pump pit in the basement floor

    What to look for: An open, uncovered sump pit (hole that the sump pump sits inside) in the basement or crawl space is not only ugly, but it can also be a hazard. A sump pit without a cover can allow moisture, soil gases, and radon to enter the home. The pump can clog with dirt and debris and eventually stop working. There's also a risk that objects, children, and pets might fall into the hole. It's for these reasons that basement sump pumps should have a gas-tight, removable cover.

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For more information on basement and crawl space problems, browse our Learning Center. If you're looking for a professional to help fix water and moisture issues in your basement or crawl space, schedule a free estimate now with the Basement Systems contractor in your area.

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