Basement Mold – Find It, Remove It, and Stop It

Basement mold is common because most basements are wet and humid with little air movement. Mold spores can blow into the house through windows, doors, and HVAC systems or be carried in on clothes, shoes, and by pets. Then, moisture causes the mold spores to grow.

Mold in the Basement

Mold in the Basement

Mold grows anywhere there is oxygen and moisture. It grows well on wood, paper (cardboard), carpet, foods, and insulation. (US Environmental Protection Agency) Other materials that support mold growth include dust, paint, wallpaper, drywall, fabric, and upholstery. Many of which are found in basements.

Mold is one of nature’s ways of breaking down wood, leaves, grass, and other organic materials into their basic organic compounds to be reabsorbed into growing organisms. While mold provides a great service to nature, it damages your home.

Finding Mold in the Basement

Basement mold smells musty. That smell is the first indication you have the beginnings of a problem. Don’t procrastinate – find the areas where it is growing, remove it, and keep it from returning. Mold begins growing within 24 hours of the spores entering your basement.

Top Places Mold Grows in Basements

Mold thrives in areas with significant moisture. Most basements have plenty of options.

  • Sump Pumps. Condensation on pipes, leaks, or an uncovered pit.
  • Water Supply Lines. Condensation or leaks.
  • Sewer Pipes. Any leaking area.
  • Dryer Vent Pipes. Condensation.
  • Bathroom Vent Pipes. Condensation.
  • Areas Below Main Floor Plumbing. Leaks from above.
  • Window Frames. Humid basement air condenses on cool glass and can run down onto wood frames.
  • HVAC System. Near intakes and vents.

Most moisture from condensation and leaks promotes mold growth on adjacent surfaces like drywall, studs, insulation, and floors. Pipe and vent moisture provides indications of where to look.

Also, check walls for areas that look dirty or have developed small black specks – what looks like an accumulation of dirt could be mold.

Use something like a flathead screwdriver to prod drywall and wood you think is moldy. If the screwdriver goes in easily, there’s a good chance you have mold.

Flooded Basement and Mold

If your basement has flooded, you will have mold growth. Everything that got wet will grow mold if left untreated. If your basement is finished, you must remove drywall and insulation and treat the entire area with one of the mold-killing and/or mold-preventing products listed below.

Removing Mold in the Basement

Removing mold from a basement is a straightforward DIY project. While it’s not expensive, it takes a lot of time. Hiring someone to do the job will cost between $500.00 and $7000.00, depending on the complexity.

For flooded basements, you should call your insurance company and a flood and restoration contractor. 

Wear Protective Gear

Mold spores aggravate asthma and can cause coughs, sinus problems, and other respiratory issues. You need to wear protective gear before removing mold.

Before you start, wear old clothes, long gloves, and make sure most of your skin is covered. You’ll also need to wear work boots or rubber boots and use an N-95 mask or a respirator and non-breathing goggles.

Note: Level 4 disposable hazmat suits cost less than $20.00. Not a big investment in your safety.

Before starting work, open all the windows and doors and set up a fan to remove contaminated air.

Clear the Area

Take movable items outside and check them for mold. Here’s what to do:

  • Cardboard items and paper. Throw out cardboard.
  • Wash and dry clothing.
  • Clean contaminated items. You can clean leather and wood.
  • Upholstered furniture may have to be thrown out or professionally reupholstered.

Note: Usually only flooded basements require this type of treatment.

Kill Mold, Then Remove It

Mold is a living organism, it needs to be killed–then removed. Scraping it off will leave spores behind that will be growing again within 24 hours. 

Most mold-killing products work within 15 minutes. Make sure you read and follow all directions on the bottle. For most products, you’ll start by spraying the mold areas and waiting the appropriate length of time. Once the spray has dried, you can remove the dead mold using dish detergent and hot water.

Another option is to encapsulate the dead spores by painting over them with a product such as Kilz.

The Best Mold-Killing Products for Basements

There are many mold killers you can use, including household and commercial products.

  • Hard Surfaces. Mix 1 part bleach with 16 parts water and spray on all affected areas.
  • Porous Surfaces. Mix 1 part liquid dish detergent (non-ammonia), 10 parts bleach, and 20 parts water. Spray liberally.
  • Borax. Safe for porous and non-porous material. Mix 1 cup of borax in 1 gallon of water. Spray or brush on affected surfaces.
  • Baking Soda. Mix half a teaspoon of baking soda into a spray bottle of water. OR combine a half cup of baking soda with one cup of water and one tablespoon of dish detergent. Brush on affected areas.
  • Benefect Botanical Disinfectant Cleaner.
  • CLR Mold and Mildew.

How to Stop Basement Mold From Returning

Basement sump pump
Courtesy: Terry Schutz – Sump pit with a tight-fitting lid

Getting rid of the mold is not the end of the war. Mold spores still exist, and they will find ways into your basement. The best way to prevent mold from recurring is to change the amount of moisture and humidity in your basement.

  • Plumbing Pipes. Ensure that no pipes are leaking.
  • Sump Pump. Check pipes for leaks and ensure the lid fits tightly.
  • All Vent Pipes. Seal dryer and bathroom vent pipes at the outside wall penetrations.
  • Wall Leaks. Seal leaks in concrete walls.
  • Eavestrough and Downspouts. Clean the eavestrough and extend downspouts at least 10’ from the house.
  • Landscaping. Make sure the topsoil is sloped away from the house. At least ½” per foot for 10’.
  • Dehumidifier. Buy a dehumidifier for the basement. Change the settings as required. About 30% in winter and around 50% in summer. (No higher than 60%.)

Do everything you can to keep humidity low. Even if you have a dehumidifier, consider setting up a fan in the basement to move air around. An open window to facilitate air exchanges is also a good idea.