You pull a dresser away from an outside wall and find a patch of gray-green spots. Or the back of a closet smells musty, or black specks are creeping across the wall above the shower. It’s tempting to grab the bleach, but there’s a safer, simpler way.
Here’s how to clean mold off walls safely, based on guidance from the EPA and CDC. We’ll cover when to call a pro, what to wear, step-by-step cleaning for painted drywall and bathroom walls, mold vs mildew, black mold, whether vinegar works and how to keep mold away.
Is This a Job You Can Handle Yourself?
If the moldy area is less than about 10 square feet (roughly 3 feet by 3 feet), EPA says you can usually handle the job yourself. EPA also flags cases that need extra caution or professional help:
• It’s bigger than that, or there’s been a lot of water damage. If you hire help, choose a contractor with mold experience and check references.
• Your heating or cooling system may be moldy. Don’t run it, since it could spread mold through the house.
• Sewage or other contaminated water caused the damage. That calls for a professional with contaminated-water experience.
• Mold may be inside the wall. A musty smell with no visible source, or a known leak behind the drywall, can mean hidden growth. Opening a wall cavity, breaking up moldy drywall or peeling wallpaper is likely to stir up mold, so consider hiring an experienced pro.
• Someone at home has health concerns. EPA advises talking with a health professional before you start. CDC notes that people with asthma or mold allergies may have severe reactions, and people with weakened immune systems or chronic lung disease may get lung infections from mold.
Before You Scrub: Fix the Moisture and Gear Up
Mold needs moisture to grow, and a little condensation can be enough. EPA’s mold course puts it plainly: moisture control is the key to mold control. Find the source first, whether it’s a dripping pipe, a leaky window frame, a bath fan that doesn’t work or condensation on a cold outside wall.
Then gear up. EPA’s homeowner guide recommends gloves and goggles without vent holes and suggests an N-95 respirator to limit how much mold you breathe in. Ordinary household rubber gloves are fine for detergent and water, and a respirator only works if it fits properly. Open a window, keep kids and pets out and lay an old towel below the work area.
How to Clean Mold Off Walls Step by Step
EPA’s method for hard surfaces is to scrub mold off with water and detergent, then dry quickly and thoroughly. Porous materials with mold growing in them may have to be thrown away. Drywall is porous, so these steps are our approach for small surface spots on painted drywall that’s still firm and intact, not for mold that has grown into the board.
On Painted Drywall
1. Mix a mild solution. Stir about a teaspoon of dish detergent into a gallon of warm water, and fill a second bucket with plain water for rinsing. Don’t add bleach, ammonia or anything else.
2. Spot test first. Flat and matte paint can scuff or turn shiny when scrubbed, so try your sponge in a hidden spot, like behind a door.
3. Dampen, don’t soak. Wring the sponge until it’s barely damp. Drywall soaks up water, and a soggy wall is exactly what mold wants.
4. Scrub gently from the outside in. Work in small circles from the edge of the patch toward the center so you don’t spread it. You don’t have to clean with a jackhammer: hard scrubbing can wear through the paint to the paper underneath.
5. Rinse and bag as you go. Wipe with a clean, damp cloth, switching cloths often. Bag used rags and paper towels before carrying them through the house.
6. Dry it fast. Towel the wall dry, then open a window and run a dehumidifier or fan. EPA says wet materials need to dry within 24 to 48 hours to avoid mold growth.
7. Check back. Look again over the next couple of weeks. A faint stain may remain, but if spots return, moisture is still getting in.
Never paint over mold: EPA says not to paint or caulk moldy surfaces, because paint applied over mold is likely to peel. Clean the wall, let it dry completely and make sure the mold is gone before you prime and repaint.
If the drywall is soft, swollen or crumbling, or mold keeps showing through the paint, the board itself is likely damaged. EPA’s guidance on wet drywall is that it can be dried in place only if there’s no obvious swelling and the seams are intact; otherwise, it should come out. Removal stirs up spores, so call a pro for anything beyond a small patch.
How to Clean Mold Off Bathroom Walls
Semi-gloss paint, common in bathrooms, handles scrubbing better than flat paint. Turn on the exhaust fan, gear up and spot test as above, then:
1. Scrub with the same solution. A soft nylon brush works well on semi-gloss walls and in the upper corners where steam collects. Rinse with clean water.
2. Check the caulk. Mold that has grown into caulk usually won’t scrub out. Cut out the old bead, clean and dry the joint, then recaulk.
3. Dry everything. Towel or squeegee the walls, and leave the fan running until the room is dry.
Mold vs Mildew: How to Tell the Difference
Mildew isn’t separate from mold. According to EPA, the word refers to certain kinds of mold, usually growth with a flat habit, and mildew often lives on shower walls, windowsills and other damp spots. Two practical clues:
• What people call mildew sits on the surface. Flat growth on tile, glass or glossy paint usually wipes off easily with detergent and water.
• Stubborn mold has dug in. Spots that won’t budge, show through paint or keep coming back have likely grown into drywall paper, caulk or grout.
Either way, the cleanup and the fix are the same.
How to Clean Mildew Off Walls
Follow the same steps with a lighter touch: gear up, wipe with your detergent solution from the edges in, then rinse and dry completely. Then fix whatever invited it, such as a weak bath fan, a window that sweats every morning or a closet on a cold outside wall.
Black Mold on Walls: Does the Color Matter?
Dark spots worry people, thanks to headlines about toxic black mold. But EPA explains that black mold isn’t a species or a specific kind of mold, and neither is toxic mold. No one can tell whether a mold is producing toxins just by looking at it.
CDC takes the same practical view: mold can look like spots of many different colors, you don’t need to know the type and whatever kind is present needs to go.
When people say black mold, they often mean Stachybotrys chartarum, which CDC describes as a greenish-black mold that can grow on high-cellulose materials such as gypsum board and paper. Treat it like any other mold.
Does Vinegar Kill Mold? What About Bleach?
For vinegar, the short answer is: not reliably. Vinegar has some antifungal activity, but research on how well it works against household mold is limited. In a 2015 lab study, Australian researchers tested five cleaning agents, including vinegar (4 to 4.2 percent acetic acid), against two molds common indoors. Vinegar held back the growth of Penicillium chrysogenum but not Aspergillus fumigatus.
The authors called vinegar’s antifungal action limited and said it may not work against the variety of molds found indoors. Keep the study’s limits in mind, too: it used petri dishes rather than walls and didn’t include bleach. The researchers called for testing on real building materials.
More to the point, the goal is removal. EPA’s remediation guidance says dead mold is still allergenic, so it has to be cleaned up, not just killed. It also says biocides such as chlorine bleach aren’t recommended as a routine part of mold cleanup, though professional judgment may call for one in special cases, such as when someone with a weakened immune system is present. Biocides are toxic to people as well as mold, and EPA says to always ventilate the area if you use one.
We’ve been making cleaners since 1997, and our advice builds on EPA’s: to clean mold off walls in a small area, skip the bleach and stick with detergent, water and a good scrub, the method EPA gives for hard surfaces. For more on bleach around the house, see the hidden dangers of using bleach for home cleaning.
Safety first: Never mix cleaners. Poison control experts at Children’s Hospital of Philadelphia warn that bleach plus ammonia makes chloramine gas, and bleach plus an acid such as vinegar makes chlorine gas. Mildew stain removers and other strong products can cause similar symptoms on their own in a closed-up room. Open a window and take a break if you feel uncomfortable.
How to Keep Mold From Coming Back
Cleaning mold off walls is only half the job. Moisture control does the rest, and EPA’s prevention tips come down to a few habits:
• Keep humidity between 30 and 50 percent. EPA’s target is below 60 percent, ideally 30 to 50. An inexpensive humidity meter shows where you stand, and an air conditioner or dehumidifier can bring it down.
• Ventilate every shower. Run the bath fan or open a window while you shower, then wipe down wet walls.
• Fix leaks fast. Dry wet spots within 24 to 48 hours, before mold gets a foothold.
• Give cold walls some air. EPA notes that mold often shows up in cold corners behind furniture, where condensation forms. Pull furniture a few inches away from exterior walls, leave closet doors cracked and insulate cold water pipes.
Finally, make wall cleaning part of your routine. It won’t stop mold without moisture control, but a gentle wipe-down keeps everyday grime from building up and helps you catch new spots early. For a simple seasonal routine, see why cleaning walls matters more in fall.
Make Wall Cleaning a 5-Minute Habit
Our company motto is simple: when you know the right thing, do the right thing. Now you know how to clean mold off walls safely and how to keep moisture from bringing it back. We also know the real reason walls get skipped: hauling out a ladder, a bucket and a sponge turns a quick job into a weekend project. That’s why we created the 5-Minute Clean Walls Bundle.
It pairs our non-toxic CleanWalls spray with a wall cleaning mop built for the job: a telescoping pole that reaches from baseboards to ceilings, a 360-degree swivel head for corners and trim, and two machine-washable microfiber mitts you can reuse again and again. The spray is safe on painted walls and comes in several scents, including unscented. No ladders, no kneeling and no harsh fumes.
It’s backed by our 60-day money-back guarantee, so you can put it to work in every room and decide for yourself.
Frequently Asked Questions
Do I need to test mold before I clean it?
Usually not. CDC does not recommend mold testing, partly because there are no set standards for how much mold in a home is acceptable and because you can’t rely on sampling to know whether someone will get sick. CDC’s advice is to safely remove the mold and prevent it from growing back.
Why does mold keep coming back on my bathroom walls?
Usually because moisture is still getting in. EPA notes that places that are often damp can be hard to keep completely mold-free, and that more ventilation and more frequent cleaning will usually prevent mold from recurring, or at least keep it to a minimum. Run the exhaust fan during and after every shower, fix slow leaks and replace caulk that mold has grown into.
Is tea tree oil better than vinegar for mold?
In the 2015 lab study described above, yes: tea tree oil was the most effective agent tested, though only in petri dishes. Use caution if you have pets: in a review of 443 cases reported to the ASPCA Animal Poison Control Center, dogs and cats exposed to 100 percent tea tree oil most often showed drooling, lethargy, weakness, poor coordination and tremors. Detergent and water is the safer choice.
Can mold on walls make you sick?
It can for some people. EPA says mold can cause allergic reactions such as sneezing, runny nose, red eyes and skin rash, can trigger asthma attacks in people with asthma who are allergic to mold and can irritate the eyes, nose, throat and lungs even in people who aren’t allergic. These symptoms can have other causes too, so if anyone at home has them, talk with a doctor.
Sources
1. A Brief Guide to Mold, Moisture and Your Home. U.S. Environmental Protection Agency.
2. Mold Cleanup in Your Home. U.S. Environmental Protection Agency.
3. What Is the Difference Between Mold and Mildew? U.S. Environmental Protection Agency.
4. Mold Course Chapter 1: Introduction to Molds. U.S. Environmental Protection Agency.
5. Mold Course Chapter 2: Why and Where Mold Grows. U.S. Environmental Protection Agency.
6. Mold Course Chapter 4: General Remediation Issues. U.S. Environmental Protection Agency.
7. Mold Remediation in Schools and Commercial Buildings Guide, Chapter 3: Investigating, Evaluating and Remediating Moisture and Mold Problems. U.S. Environmental Protection Agency.
8. Mold. Centers for Disease Control and Prevention.
9. Facts About Stachybotrys chartarum. Centers for Disease Control and Prevention.
10. An Evaluation of Antifungal Agents for the Treatment of Fungal Contamination in Indoor Air Environments. Rogawansamy, Gaskin, Taylor and Pisaniello, International Journal of Environmental Research and Public Health (2015).
11. Household Cleaners. Poison Control Center, Children’s Hospital of Philadelphia.
12. Concentrated Tea Tree Oil Toxicosis in Dogs and Cats: 443 Cases (2002 to 2012). Khan, McLean and Slater, Journal of the American Veterinary Medical Association (2014).