What you need to clean mold safely

Mold on a wall can be cleaned with household supplies if the affected area is small — typically less than 10 square feet. You will need white vinegar or a diluted bleach solution, a spray bottle, a stiff brush, rags or paper towels, and gloves. Wear an N95 mask if you have one, because mold spores become airborne when you scrub. Open windows and doors to ventilate the room while you work.

For small patches, white vinegar is safer than bleach and works well on most surfaces. Mix it undiluted in a spray bottle. For bleach, mix one cup of bleach per gallon of water — never mix bleach with ammonia or other cleaners, as this creates toxic fumes. If the mold covers more than 10 square feet, or if it is inside your walls or in your HVAC system, call a mold remediation professional instead of attempting it yourself.

Key Takeaways

  • Small mold patches on walls can be cleaned with white vinegar or diluted bleach, a brush, and gloves.
  • Spray the affected area, let it sit for 10 to 15 minutes, then scrub and wipe dry with clean rags.
  • Mold returns if the wall stays damp, so you must find and fix the moisture source — a leak, poor ventilation, or condensation.
  • Mold larger than 10 square feet, or mold inside walls or ducts, requires professional remediation.
  • After cleaning, keep the room dry by running a fan, opening windows, or using a dehumidifier if humidity stays above 50 percent.

Step-by-step cleaning with vinegar

Spray white vinegar directly onto the moldy area until it is wet. Do not dilute it — full-strength vinegar is more effective. Let it sit for 10 to 15 minutes so the acid can kill the mold spores. The smell is strong but harmless and fades as it dries.

Scrub the area with a stiff brush or old toothbrush, working in circular motions to break up the mold. For stubborn spots, scrub harder or let the vinegar sit longer before scrubbing. Wipe the area clean with a damp rag, then dry it completely with a dry cloth or paper towels. If mold remains, repeat the process.

Once the wall is clean and dry, spray the area lightly with vinegar one more time and let it air-dry. This helps prevent the mold from returning when ready. Vinegar does not leave a toxic residue and is safe to use around children and pets.

Step-by-step cleaning with bleach

Mix one cup of bleach with one gallon of water in a bucket. Pour the solution into a spray bottle. Spray the moldy wall until it is saturated, then let it sit for 10 minutes. Bleach works faster than vinegar but is harsher on some surfaces and toxic if ingested, so keep children and pets away while you work.

Scrub the area with a stiff brush, using firm pressure to remove all visible mold. Wipe the wall clean with a damp rag, then dry it thoroughly with a clean cloth. Rinse the area one more time with plain water to remove any bleach residue, then dry again. Bleach can lighten or discolor some paints, so test it on an inconspicuous spot first if you are unsure.

Do not mix bleach with vinegar, ammonia, or any other cleaner. The combination creates chlorine gas, which is dangerous. If you accidentally mix chemicals, leave the room when ready and open all windows and doors.

Finding and fixing the moisture source

Mold grows only where moisture is present, so cleaning alone will not stop it from returning. Look for the source: a water leak from a pipe or roof, condensation from poor ventilation, or a damp basement or crawlspace. Check the wall behind and above the moldy spot for signs of a leak — water stains, soft drywall, or peeling paint.

If the mold is near a window, the problem is likely condensation from cold glass meeting warm, humid air inside. Wipe the window dry each morning, open the window slightly to let moisture escape, or run a fan to move air across the glass. If the mold is on an exterior wall in a cold climate, it may be caused by poor insulation allowing cold air to reach the inside surface.

If you find a leak — from a roof, pipe, or foundation — repair it before the mold will stop returning. A small roof leak or plumbing drip may seem minor, but it will feed mold indefinitely. If the leak is in a wall or ceiling, or if you cannot locate the source, call a plumber or contractor to investigate.

Controlling humidity to prevent mold

Indoor humidity above 50 percent encourages mold growth. Measure humidity with an inexpensive hygrometer, available at hardware stores. If humidity is consistently high, run a bathroom exhaust fan during and for 20 minutes after showers, open windows on dry days, or use a dehumidifier in damp rooms like basements.

In kitchens, turn on the exhaust fan while cooking and leave it running for 15 minutes after you finish. In laundry rooms, vent the dryer to the outside — never into the attic or crawlspace. If you have a basement, seal cracks in the foundation and may support the ground slopes away from the house so water does not pool against the walls.

Air conditioning naturally removes moisture from the air, so running it during warm months helps. In winter, use a humidifier only if humidity drops below 30 percent, because very dry air can damage wood and cause other problems.

When to call a professional

Call a mold remediation company if the moldy area is larger than 10 square feet, if mold is visible inside walls or in your HVAC ducts, or if you have a large water leak you cannot repair yourself. Professionals have equipment to detect hidden mold, remove contaminated materials safely, and treat the area to prevent regrowth.

If you have a health condition that makes you sensitive to mold — such as asthma, a weakened immune system, or a mold allergy — consider hiring a professional even for small patches. Mold spores released during cleaning can trigger symptoms. A professional will contain the work area and use HEPA filters to capture spores before they spread through your home.

After a professional remediation, ask what caused the mold and what repairs they recommend. If they cleaned the mold but did not fix the moisture source, it will return.

Protecting yourself while cleaning

Wear gloves to protect your skin from mold and cleaning chemicals. An N95 mask reduces the number of spores you inhale — look for one marked "NIOSH-approved" at a hardware or medical supply store. Safety glasses protect your eyes if you are spraying overhead. Wash your hands and face after cleaning, and wash your clothes separately from other laundry.

Ventilate the room by opening windows and doors, or by running a fan that pulls air out of the room — not one that recirculates air within the room. If you feel dizzy, short of breath, or develop a headache while cleaning, leave the room when ready and get fresh air. These can be signs of exposure to mold spores or cleaning fumes.

Do not sand, scrape, or use a pressure washer on moldy walls, because these methods release large amounts of spores into the air. Wet cleaning methods — spraying and wiping — keep spores contained.

Frequently Asked Questions

Can I paint over mold to cover it?

No. Paint does not kill mold and will not stop it from spreading. The mold will continue to grow under the paint, and the paint will eventually peel. You must clean and dry the wall completely before painting, and you must fix the moisture source or the mold will return.

Is black mold more dangerous than other mold?

Black mold is not inherently more toxic than other molds, though some species of black mold produce toxins. Any mold can trigger allergies or asthma symptoms in sensitive people. Clean it the same way you would clean any other mold, and see a doctor if you develop symptoms after exposure.

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

If you fix the moisture source, mold should not return. If the wall stays damp, mold can reappear within days or weeks. If mold returns quickly after cleaning, the moisture source is still present — investigate further or call a professional to locate it.

Can I use a dehumidifier to prevent mold?

A dehumidifier helps if humidity is consistently above 50 percent, but it is not a substitute for fixing leaks or improving ventilation. Use it alongside other moisture control methods — fixing the roof, venting the dryer outside, and opening windows on dry days.

What if the mold smell remains after cleaning?

Lingering smell usually means moisture is still present or mold is hidden in the wall. Open windows to air out the room, run a fan, and check for leaks or damp spots. If the smell persists for more than a few days, the moisture source may be inside the wall and you may need a professional to locate it.