What fungus is and where it grows in homes

Fungus is a living organism that feeds on organic material — wood, drywall, fabric, grout, and soap scum are all food sources. Unlike mold, which is a type of fungus that spreads through spores in the air, other fungi grow as visible patches, discoloration, or slimy coatings on surfaces. You'll find fungus in bathrooms, basements, kitchens, and anywhere moisture sits for more than a few hours.

The difference matters for cleaning. Mold requires containment and sometimes professional removal. Most household fungus — the kind you see on shower tiles, around sink drains, or on basement walls — you can clean yourself with the right approach and materials. The goal is to remove the visible growth and the moisture that feeds it, so it doesn't return within days.

Key Takeaways

  • Fungus grows on surfaces where moisture stays wet for hours; cleaning it means removing both the visible growth and the water source.
  • Most household fungus can be cleaned with a stiff brush, household cleaners like bleach or vinegar, and good ventilation.
  • After cleaning, dry the surface completely and improve air circulation to prevent fungus from returning within a week.
  • If fungus covers more than 10 square feet, returns after cleaning, or grows inside walls or insulation, call a professional.
  • Wearing gloves and eye protection protects your skin and lungs from the cleaning chemicals and fungal spores you'll disturb.

Supplies you need before you start

Gather everything before you begin, so you don't have to leave the area mid-job and let spores settle elsewhere in your home. You'll need: rubber gloves, eye protection, an N95 mask (optional but useful if you're sensitive to spores), a stiff-bristled brush or old toothbrush, clean rags or paper towels, and a cleaning agent. Bleach, white vinegar, hydrogen peroxide, or commercial mold and mildew cleaners all work — bleach is fastest on hard surfaces, vinegar is safer around plants and pets, and hydrogen peroxide is gentler on fabrics.

Open windows and doors in the room before you start. Fungus releases spores when you disturb it, and ventilation carries them outside instead of deeper into your home. If the area is small (a few tiles, a corner of grout), you don't need a respirator. If you're cleaning a large bathroom or basement wall, an N95 mask reduces the spores you breathe in.

Step-by-step cleaning for hard surfaces

For tile, grout, porcelain, and sealed stone: spray or explore your cleaner directly onto the fungus. Let it sit for 5 to 10 minutes — this gives the chemical time to kill the organism and loosen it from the surface. Scrub with a stiff brush in circular motions, pressing hard enough to remove the discoloration but not so hard that you damage the grout or finish. Rinse thoroughly with clean water and dry when ready with a clean rag.

If the fungus doesn't come off on the first pass, repeat the process. Stubborn growth on grout may need two or three applications. For bleach, never mix it with ammonia or other cleaners — the fumes are toxic. If you're using vinegar, the smell is strong but harmless; it fades as it dries. After cleaning, leave the area open to air for at least an hour before closing the door or window.

Cleaning fungus from porous surfaces

Drywall, wood, and fabric are harder to clean because fungus can grow into the material, not just on top of it. For small patches on drywall or wood trim, spray with a diluted bleach solution (1 part bleach to 10 parts water) or hydrogen peroxide. Let it soak for 10 minutes, then wipe with a clean rag. Do not scrub hard — you'll damage the surface and push spores deeper in.

For fabric — shower curtains, bath mats, or upholstered furniture — wash in hot water with detergent if the item is washable. If it's not, spray with vinegar or hydrogen peroxide, let it dry completely in sunlight (UV light kills fungus), and then air it in a dry room for several days. If the fungus smell doesn't fade or the discoloration remains, the item may need to be replaced; fungus in fabric is harder to fully remove than on hard surfaces.

Preventing fungus from returning

Fungus returns when moisture returns. After cleaning, your job is to keep the surface dry. In bathrooms, run the exhaust fan during and for 20 minutes after showers. Wipe down shower walls and the tub surround with a squeegee or dry cloth after each use. Leave the shower door or curtain open to air out. In kitchens, wipe spills and splashes when ready, and don't let damp cloths sit in the sink.

In basements and crawl spaces, use a dehumidifier to keep humidity below 50 percent. Check for leaks around pipes, windows, and foundation cracks — water intrusion is the most common reason fungus keeps coming back. If you clean the same spot three times in a month and it returns each time, the moisture source is still active, and you need to find and fix it before cleaning again.

When to call a professional

Clean it yourself if the fungus covers less than 10 square feet, is on a surface you can reach and see clearly, and doesn't return within a week of cleaning. Call a professional if the fungus covers a large area, grows inside walls or insulation, returns repeatedly in the same spot, or if you find it in your HVAC ducts or crawl space. Professionals have equipment to dry hidden moisture and can identify whether the growth is fungus, mold, or something else that requires different treatment.

Also call a professional if you have respiratory problems, are immunocompromised, or are pregnant — exposure to fungal spores carries more risk for you, and a professional can handle the job safely. If you're unsure whether what you're seeing is fungus or mold, take a photo and describe the location to a local mold inspector or your county health department; they can advise whether it's safe to clean yourself.

Frequently Asked Questions

Can I use bleach on all surfaces?

Bleach works well on tile, grout, and sealed stone, but it can damage or discolor wood, fabric, and some natural stones like marble. Test it on a hidden area first. Never use bleach on anything porous unless you're sure it won't stain. Vinegar or hydrogen peroxide are safer choices for wood and fabric.

Why does fungus come back so fast?

Fungus returns when moisture returns. If you clean but don't fix the water source — a leaky pipe, poor ventilation, or standing water — the fungus will regrow within days or weeks. Cleaning removes what you can see; drying and ventilation prevent it from coming back.

Is it safe to breathe in fungal spores while cleaning?

Small amounts of spores from household fungus are not dangerous for most people. If you have asthma, allergies, or a weakened immune system, wear an N95 mask and may support good ventilation. If you feel dizzy, short of breath, or develop a rash during or after cleaning, stop, leave the area, and get fresh air.

What's the difference between fungus and mold?

Mold is a type of fungus that spreads through airborne spores and can grow inside walls and insulation. Most visible household fungus — slimy coatings on tile, discoloration on grout — is not mold and can be cleaned with basic supplies. If you're unsure, a professional can identify it.

Do I need to replace drywall if fungus grows on it?

Not always. Small surface patches can be cleaned and the area dried. If the drywall is soft, crumbles, or smells musty after drying, the fungus has penetrated deep and the drywall should be replaced. This usually means there's also a moisture problem inside the wall that needs to be fixed first.