The Basic Steps to Remove Fungus from Drywall and Plaster

Fungus on walls comes off with a combination of cleaning solution, scrubbing, and drying. For small patches (less than 10 square feet), you can handle this yourself with household supplies: a spray bottle of diluted bleach or white vinegar, a stiff brush, and clean rags. Spray the affected area, let it sit for 10 to 15 minutes, scrub firmly, wipe away the dead fungus and moisture, and then dry the wall completely with a fan or open windows.

For larger areas or if the fungus returns quickly after cleaning, the underlying moisture problem is the real issue — and that one you cannot solve by scrubbing alone. Fungus grows because the wall stays damp. Once you remove the visible growth, you must find and stop the source of that moisture, or the fungus will come back within weeks.

If the wall feels soft, crumbles when you touch it, or the fungus has penetrated more than a quarter-inch into the drywall, the material itself is compromised and needs to be cut out and replaced. This is the point where a professional assessment is worth the cost, because removing and replacing drywall is not a cleaning job anymore — it is a repair.

Key Takeaways

  • Small fungus patches can be cleaned with a bleach or vinegar solution, a brush, and thorough drying, but the wall must dry completely afterward or the fungus returns.
  • Fungus always means moisture is present; cleaning the visible growth without stopping the moisture source will result in regrowth within weeks or months.
  • If the wall feels soft, crumbles, or smells strongly of mold, the drywall is damaged and needs replacement, not cleaning.
  • Ventilation and dehumidification are as important as the cleaning itself — a wet wall will grow fungus again no matter how thoroughly you scrub it.
  • Patches larger than 10 square feet or fungus in HVAC ducts should be assessed by a professional before you begin cleaning.

What Cleaning Solutions Actually Work

Diluted bleach is the most common choice and kills fungus on contact. Mix one part household bleach (typically 3 to 6 percent sodium hypochlorite) with three parts water in a spray bottle. Spray the wall until it is visibly wet, wait 10 to 15 minutes, then scrub with a stiff-bristled brush. Bleach works on non-porous surfaces like tile and painted drywall, but it does not penetrate deep into porous materials and can damage some paints or fabrics.

White vinegar (5 percent acetic acid) is slower than bleach but safer to handle and does not produce toxic fumes. Spray undiluted vinegar directly on the fungus, wait 30 minutes to an hour, then scrub and rinse. Vinegar is gentler on finishes and works well on porous surfaces, though it takes longer to kill the fungus.

Hydrogen peroxide (3 percent, the kind sold in drugstores) also kills fungus and is safer than bleach, though less powerful. Spray it on, wait 10 minutes, scrub, and rinse. It breaks down into water and oxygen, leaving no toxic residue.

Do not mix bleach with ammonia, vinegar, or other cleaners — the chemical reaction produces toxic chlorine gas. Use only one cleaning agent at a time, and ventilate the room well while you work. Wear gloves and eye protection, and avoid breathing the spray or fumes.

Drying the Wall Is as Important as Cleaning It

After you scrub away the visible fungus, the wall must dry completely. Fungus spores are everywhere in the air, and a damp wall will grow new fungus within days if you do not remove the moisture. Open windows and doors to create cross-ventilation, run a box fan pointed at the wall, or use a dehumidifier if the room is very humid.

In bathrooms and kitchens, turn on the exhaust fan during and for at least 30 minutes after cleaning. If the wall is in a basement or other naturally damp space, run a dehumidifier continuously until the wall feels completely dry to the touch — this may take 24 to 48 hours. A moisture meter (available at hardware stores for $15 to $40) can tell you when the wall has dried enough; aim for a reading below 16 percent.

If the wall dries within a day or two and the fungus does not return, the moisture was temporary — perhaps from a spill, a leaky window, or high humidity during a rainy week. If the wall stays damp or the fungus comes back, there is an ongoing moisture source you need to find.

Finding and Stopping the Moisture Source

Fungus returns because the wall is still wet. The moisture is coming from somewhere: a roof leak, a plumbing leak inside the wall, condensation from poor ventilation, groundwater seeping through the basement, or exterior water running down the outside of the wall and finding its way in.

Look for these signs to narrow down the source. If the fungus is near a window or door, check the seal and the caulk around the frame — water may be leaking in from outside. If it is on an exterior wall near the foundation, water may be entering from the ground. If it is in a bathroom or kitchen, the leak may be from a pipe or from moisture that the exhaust fan is not removing fast enough. If it is in a basement, the wall may be absorbing groundwater.

Once you identify the source, stop it: caulk a leaking window, repair a roof leak, fix a plumbing leak, improve ventilation, or install a sump pump or interior drain system if groundwater is the problem. Until you stop the moisture, cleaning the fungus is temporary.

When to Call a Professional

Call a professional if the fungus covers more than 10 square feet, if it returns within a month of cleaning, if the wall feels soft or crumbles, or if you cannot find the moisture source. A mold remediation contractor or a structural inspector can identify hidden leaks, assess whether the drywall is salvageable, and recommend the right repair.

You should also call a professional if the fungus is in your HVAC ducts, crawl space, or attic — these areas are harder to access and the fungus can spread through the air system. If anyone in your household has respiratory problems, asthma, or a weakened immune system, have a professional assess the situation before you begin cleaning, because disturbing mold can release spores into the air.

A professional assessment typically costs $200 to $500 and may save you thousands by catching a hidden leak or structural damage early. If the drywall needs to be replaced, a contractor can do it correctly and may support the new wall is installed in a way that resists future moisture.

Preventing Fungus from Growing Back

After you have cleaned the wall and fixed the moisture source, keep the wall dry. In bathrooms, run the exhaust fan during showers and for 20 to 30 minutes afterward. In kitchens, use the range hood while cooking. In basements and crawl spaces, run a dehumidifier if the humidity stays above 50 percent. In bedrooms and living areas, open windows on dry days to let air circulate.

Check the wall regularly — once a month is enough — for any sign of new fungus. If you see a small spot, clean it when ready with vinegar or bleach before it spreads. Keep gutters and downspouts clear so water runs away from the foundation. Caulk any gaps around windows, doors, and pipes. These small steps prevent the conditions that allow fungus to grow.

Frequently Asked Questions

Is the fungus on my wall dangerous to my health?

Most household mold is not toxic, but it can trigger allergies or asthma in sensitive people, especially if there is a lot of it or if you disturb it and release spores into the air. If anyone in your home has respiratory problems, have a professional assess the situation before you begin cleaning. Otherwise, standard precautions — gloves, eye protection, and ventilation — are sufficient.

Can I paint over fungus to hide it?

No. Paint will not kill fungus, and the fungus will continue to grow under the paint, eventually causing the paint to peel and the wall to deteriorate. Always clean and dry the wall first, then address the moisture source, before you paint.

What if the fungus is on wallpaper or fabric?

Wallpaper and fabric trap moisture and are harder to clean than painted drywall. If the fungus is on wallpaper, remove the wallpaper first, clean the wall underneath, dry it completely, and then decide whether to repaint or re-wallpaper. If the fungus is on a curtain or upholstered furniture, wash or dry-clean the item and move it away from the damp wall.

How long does it take for fungus to come back after cleaning?

If the moisture source is fixed and the wall dries completely, fungus should not return. If it comes back within a few weeks, the wall is still damp, which means the moisture source is still active or the wall did not dry thoroughly enough. This is a sign you need to investigate further or call a professional.

Do I need to wear a respirator mask while cleaning?

For small patches, a standard dust mask is adequate if you are concerned. For larger areas or if you are sensitive to mold, an N95 or P100 respirator offers better protection. Ventilate the room well, and if you feel lightheaded or have trouble breathing, stop and leave the room when ready.