When you've lived with musty basement smells for long enough, it's easy to start thinking that basements are supposed to be like this. Since it's dark down there and close to the earth, isn't this just something you need to live with?
Not necessarily. It's true that basements' qualities factor into the musty smells—being fully or partially below-grade, less light, less fresh air. But not all basements need to become musty. Plus, basements that are already musty can often be turned around with a few simple, inexpensive methods.
What Causes a Basement's Musty Smell
You know it instantly. It's unique and unmistakable: basement smell. You'll never walk into a garage or even a bathroom and mistake its smell for that of a basement.
Basement musty smell is variously described as earthy or meaty, or similar to rotten wood, wet socks, mushrooms, or a wet dog. Adding in certain tangy or sweet notes brings the odor closer to that of a truly musty basement.
Identifying and understanding the causes of a basement's musty smell is vital because these causes directly correlate to your solutions:
Mold and Mildew
Mold and mildew are the chief drivers of basement musty smell. Both are fungi that thrive on water, oxygen, and food.
While often confused with each other, mold and mildew are actually different. Mold is usually thicker and higher, even developing a moss-like, fuzzy appearance. By contrast, mildew is flat. Mold can be colorful, ranging from dark greens to grays and blacks. Mildew is usually brown or gray, eventually turning to a white powder.
Other Basement Smell Contributors
With mold and mildew forming the majority of a basement's musty smell, other causes can round off the smell and give it that singular odor:
- Damp Materials: Drywall, fiberglass and rockwool insulation, and especially wood in all forms can add to a basement's musty smell when wet and not allowed to properly dry out.
- Sewage: Sewage lines typically run through the basement before continuing outside. Sewage problems can range from improperly fitted pipes that emit odors to liquid sewage spills from pipes.
- Animal Waste: Rodent droppings look like dark grains of rice and can contribute to the sour smell in a basement. Not only that, rodent feces can spread diseases such as hantavirus and salmonella.
- Iron Ochre or Iron Bacteria: Iron ochre looks like slimy mud. In fact, this vibrant red-brown wet material is a bacteria that feeds off of iron and adds a rotten-egg smell to the basement.
Steps to Ridding Your Basement of Musty Smells
Always begin with mold/mildew eradication, which also means eradicating or limiting moisture in the basement. When you rid your basement of mold and mildew, you have taken care of the main source of the basement musty smell.
Make Your Basement as Dry as Possible
Begin drying your basement by first drying the outside of your basement. Effective exterior water management can often stop the water before it even enters the basement.
- Create a slope so that the soil next to the house is pitched down and away.
- Create a drainage system that takes water far away from the house.
- Create berms, barriers, or French drains in the yard to divert water.
- Protect basement windows with window well covers.
- Waterproof and dampproof the foundation wall with a liquid or solid membrane.
- Install or fix drainpipes and gutters or clear them out.
Inside of the basement:
- Coat the inside of the foundation with ready-mix waterproof coatings.
- Install or fix a sump pump.
- Install a system of dehumidifiers.
Clean or Replace Moldy, Mildewy, or Damp or Rotted Materials
All wet or damp materials must be dried out as quickly as possible and cleaned or removed and replaced.
Floating (unattached to the subfloor) hard floorings such as laminate and vinyl can be pulled up and dried. If the underside of the laminate is waterlogged, it should be replaced.
Remove baseboards to pull back wall-to-wall carpeting and padding and examine the bottom. Circles usually indicate mildew spots. Black mold will be obvious as dark stains.
Check and Repair Leaky Pipes
Your home is laced with pipes everywhere, starting with the water shutoff (where the water line enters the home, moving to the water heater, and back out again to bathrooms and the kitchen. Soil stacks carry unpleasant odors out of the house and equalize pressure on the pipes.
Inspect all visible pipes for leaks. Hidden pipes may run through ceilings and leak onto the drywall. It's often worthwhile to hire a plumber to also check for pipe leaks.
Hire a Pest Control Company
For the occasional mouse or two, set traps. But if you have a persistent problem with rodents and insects, you may want to place your home under a pest control contract.
After an initial treatment, pest control technicians return on a regular basis. Pest control contracts are also important to have in place if you intend to sell your home, as they can often be a condition of sale.
Clean Any Iron Ochre
Wearing waterproof gloves, use a putty knife to scrape away large portions of the iron ochre slime. Follow with a rust remover. Likely, you will not be able to remove all of the color stains. But the majority of the odor-producing iron ochre will be gone.