Removing Moldy, Mildewy Basement Odors

Clean Basement and How to Keep it Clean.

How to Rid the Basement of Smelly Odors

Removing Basement Odors

Don’t feel bad because basements frequently have that old, mildewy smell. When something smells “off”, it simply needs to be cleaned, decaying items removed, and the environmental conditions changed to stop further odors from developing.

Deodorizers and air fresheners make it smell better, but the effect is a temporary mask. It is far more important in the long run to get the odor under control and fix the problem cause before it worsens.

There are 2 easy steps to take when it comes to basement odors:

  1. Remove or repair the problem that is causing the smell.
  2. Clean the area to reduce the smell, control and prevent any odor from coming back.

Luckily, there are some common things that cause odor to develop, and they are easily fixed. Find the solution to your odor problem by following the tips below.

Causes of Old, Musty, Moldy, Mildewy & Smelly Basements

Basements are one of the most common odor producers in the home, right behind the refrigerator and the cat box. There are several things that can cause basement odors. These are the most common causes of smelly basements and what you need to do to fix it:

Inadequate Cleaning

The Problem: You know the old saying: “Out of sight, out of mind”. Dust, dirt, grime, cobwebs and decay develops and builds up over time. Rodents and insects can take up residence without you knowing and create foul odors, unhealthy and unsanitary living conditions for you and your family. Mold and mildew put off foul odors that can be absorbed and spread to stored items.

The Fix: Give the basement a good overall cleaning. Start at the ceiling, clean down the walls and behind every item. Use bleach, borax or vinegar to clean and control odor. Clear out old junk stored in the basement. Remove things that absorb moisture or can put off bad smells such as clothing or carpet and things packed in cardboard boxes.

Opt to store items in plastic storage containers with secure lids. There are many different sizes and some that can hang folders for important papers. Label containers so you can easily find what you’re looking for.

If you had clothes in cardboard and there are items you want to keep, try washing on the hottest setting that is safe for the garment. If there are heirlooms, try a professional. Unfortunately, some clothes might not make it.

If you were storing upholstered furniture, seat cushions, etc. some of these items may be too stinky to save, some may be saved by vacuuming and spot cleaning them.

A clean area doesn’t just look better, it smells better too. Clutter reduces air flow and mildew frequently develops on decaying items.


The Problem: One of the most common problems with a basement is the amount of moisture that can happen. Moisture causes mold, mildew, bacteria, fungal growth and causes wood, fabric and paper to start to rot. The very first thing to do is to get the basement dry. Even before you start cleaning, get the humidity down.

The Fix: You need to dry it out. To do this, use a dehumidifier and air out the location by opening windows. If you see water leaking from faucets or pipes or cracks in your foundation, get them repaired to stop water from leaking into the area. If you see water stains, investigate the source and get it fixed as well.

If there is a moisture problem, unfortunately anything not stored up off the floor (like a rolled up carpet), stored in cardboard boxes and some wood items may be too bad to keep.

Poor Air Circulation

The Problem: Poor air circulation all by itself isn’t a cause of basement odor, but it does make it worse by allowing air to become stagnant which can allow bad smells to become more obvious. Moving air also helps water to evaporate. Stagnant air makes mold and mildew worse when spores are released into the air and easily spread to other damp areas.

The Fix: Get the air moving by opening a window, turning on a fan, and opening the doors.

Low Light and Temperature

The Problem: Low lighting and air temperature can also promote odors. Dark, damp low light and air circulation creates the perfect environment for mold and mildew to grow or basement contents to decay unseen.

The Fix: Bring up the air temperature by using a portable area heater, turn on the lights and open the curtains. Heated rooms help water to evaporate and you’ll be able to see the problem areas more easily in the light.

Mold and Mildew Growth

The Problem: Mold, mildew and fungus grows in damp areas with low lighting and thrive with poor air circulation. These organisms put off a gas that we most commonly associate with a smelly basement. Poor air circulation makes the smell worse and allows the spread of mold and mildew to other areas with time.

The Fix: You need to clean up moldy areas and scrub away visible stains. Borax is the perfect thing to use to clean this as it’s a natural mineral cleaner that also kills fungus (fungicide) and prevents further growth.

To Clean It: To make your mold and mildew cleaning solution mix the following in a bucket or add what you can to a spray bottle:

  • 1 cup of borax cleaner
  • 1 gallon of hot water

Use a scrub brush to clean the area and follow with a rinse of clean water as borax will leave a residue.

To Remove Stains: Remove stains and fight off mold and mildew regrowth with a bleach and water solution:

  • 2 cups of bleach
  • 2 quarts of hot water

Pour the solution into a spray bottle and work your way around spraying areas where you see visible staining, or suspect are causing odor problems. Keep in mind that there is water in this solution, so use sparingly to avoid contributing to a moisture problem. Bleach will liquefy, sanitize and remove the color on contact, depending on the surface it’s being used on.

Chlorine bleach is a very good sanitizer but I don’t use bleach frequently. Because it bleaches everything it comes into contact with I find it can cause more harm than good if you accidentally get it on an unintended surface. But this is one project where it is justified because it works like no other cleaning chemical will do.

Bleach is strongly alkaline and is very harsh. It may be a commonly used product, but you should respect it too. It will erode and corrode many things, and make the surface very slippery. It will burn your skin if it is not rinsed off. Bleach also removes the color from fabric on contact with no second chances. So rinse the area with plain water after using. Also, never use bleach in conjunction with any other cleaning product. It will react to many things and put off a toxic gas that could be very serious in an area of low air circulation.

How to Keep Your Basement Smelling Fresh

There are several things that you can do to keep the odors at bay and keep your basement smelling fresh and clean.

  • Keep the home and the basement adequately ventilated. Air needs to flow through the home to allow for it to be kept clean. To make sure this happens, have your air ducts cleaned and also have your ventilation system checked yearly.
  • Control the humidity. The biggest odor causing problem in homes is that of mildew and mold. Use ventilation, windows, dehumidifiers and effective means for keeping water out to keep the level of humidity down.
  • Clean your dryer vent. Start outside where it exits and follow it down into the home to the base of the dryer. Blocked dryer vents allow moisture to build up in the home. If the dryer is in the basement, this can be the original source of basement odors to start with. Rodents can take up residence in the vent attracted to the lint that makes a nice nest and warm temperatures
  • Waterproof the basement. Water is the cause of many air quality problems. Make sure your basement is waterproof. A small leak can cause a tremendous amount of moisture and cause the other side of the home to smell bad.
  • Keep the home clean. Get the garbage out of the house quickly; keep the floors clean and pills cleaned up. Take care of those places that people like to avoid like the basement and the garage. Use products that will eliminate mold and mildew from your home.
  • Repair all leaks. If you suspect that your foundation or the beams in your home have gotten wet or damaged, have a professional come out and make sure. Weakened structures are not safe and will cause you to become injured and cause odor in the home.

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