How to Remove Mold from Drywall (And When to Call a Professional)

Drywall, or sheetrock, is a cost-effective building material, but it’s prone to water damage and mold. If you notice or suspect mold is growing on your drywall, take action immediately. For this article, we interviewed mold assessor Mike Kapur and cleaning specialist Raymond Chiu to teach you how to remove mold from unpainted and painted drywall. Plus, learn how to recognize and prevent mold growth and how to know when to call a professional for mold remediation.

How to Kill & Treat Mold on Drywall

On painted drywall, spray the mold with a mold-killing solution (bleach, baking soda, or vinegar) and scrub the area with a soft bristle brush until all the mold is gone. Let the area dry completely, pointing a fan at it to speed up the process. If the drywall is unpainted or very moldy, cut it out and replace it.

Section 1 of 5:

How to Remove Mold from Painted Drywall

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1
Put on protective gear and cover your work area. Because mold spores spread easily, protect yourself and the rest of your home by wearing PPE (personal protective equipment), such as an N95 mask, long rubber gloves, protective goggles, and if possible, a full body protective suit. Remove any furniture you want to protect and tape plastic sheeting to the floor. Open a window to ventilate the room, and seal any doors that lead to other parts of the house.^{[1]
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- Because you’ll likely need to work with strong chemicals to remove mold, it’s important to work in a well-ventilated area.
- Paint can act as a protective layer which keeps the mold from getting on the drywall itself. If you catch it early, it’s usually possible to remove it with cleaning solutions rather than having to replace the drywall itself.
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Spray the drywall with a mold-killing solution of your choice. There are several different cleaning agents that kill mold, though some are stronger than others. Pour your preferred solution into a spray bottle and lightly spray it on the mold. Be careful not to drench the area, as too much moisture can make the mold worse. Here are some effective mold-killing solutions you can try:^{[2]
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- Bleach: Mix 1 part bleach with 3 parts water for an effective mold-killing solution. Do not mix bleach with any other chemicals, and work in a well-ventilated area so you don’t breathe in the strong fumes.
- Baking soda: Combine 1 part baking soda with 5 parts water for a mild cleaning solution. This is the safest mold cleaner, so it’s a good option if you have pets or children.
- Vinegar: Use straight vinegar or mix it with water in equal parts. This method is a bit stronger than baking soda but is still natural and safe to use around children and pets. It does have a strong scent, however.
- Commercial mold cleaners: Commercial mold and mildew cleaners, like Concrobium Mold Control, are designed to effectively eliminate mold and musty odors. They also help prevent regrowth by creating a protective barrier. Commercial mold cleaners are strong chemicals, however, and shouldn’t be used around children or pets.
- Unscented detergent: Combine unscented detergent with a small amount of water for a safer chemical option. Using an unscented detergent means you’ll still be able to detect the smell of mold without interference.
- Whatever solution you choose, Chiu says to “do a test spot treatment in an inconspicuous spot” to make sure it won’t damage the paint.^{[3]
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  Expert Source
  
  Raymond Chiu
  House Cleaning Professional
  
  Expert Interview. 15 October 2019.}
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While the cleaning solution is still wet, scrub the moldy area with a soft bristle brush or an old toothbrush. A sponge with an abrasive side will also work. Scrub the area until you no longer see any mold or discoloration. Don’t scrub too hard, though, or you could damage the drywall.^{[4]
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Because mold grows due to moisture, make sure to dry the area thoroughly. Point a fan at the wall and let it run for as long as necessary until the sheetrock is completely dry. While you wait, dispose of any materials used to clean the spot and disinfect reusable tools. Once the wall is dry, repaint it with a stain-blocking paint if any discoloration remains.^{[5]
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Section 2 of 5:

Signs of Mold on Drywall

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Discoloration and stains Mold typically appears on drywall as discoloration and black, gray, green, yellow, or brown dots or clusters. Water stains also indicate moisture issues that can lead to mold growth. Here are a few common types of mold and where they’re likely to be found:^{[6]
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- Black mold: Black mold is often found in houses and on surfaces with excessive moisture damage. It can potentially produce mycotoxins that can harm people and pets if left untreated for a long period of time.
- Blue mold: Blue mold has a bluish-green color and is often found in drywall, wallpaper, ceilings, and insulation that has been damaged by water. It requires little moisture to develop.
- White mold: White mold often grows in cool, damp environments, like basements.
- Green mold: Green mold is often found in dark, damp areas and is known to grow in bathrooms and dark corners.
- Kapur says, “There's different types of mold, but they come in a million different colors—black is just one that people are afraid of. It comes in white, gray, [and] beige. Usually, you can identify it on a cleaner piece of surface where you see little spots [of those colors].”^{[7]
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  Expert Source
  
  Mike Kapur
  Certified Mold Assessor & Home Inspector, Sonic Home Inspections
  
  Expert Interview. 19 August 2020.}
When there is moisture behind a wall, the paint can crack, peel, or bubble. The walls may also warp, bow, or bulge when there are water issues, which can lead to mold. Fuzzy, slimy, or powdery spots are also a strong indication of mold.^{[8]
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Most gives off a recognizable musty odor, so if you notice a stuffy, stale smell, it’s most likely mold. Try smelling near electrical outlets to get a better whiff, as they provide the best access to the space behind your walls.^{[9]
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Section 3 of 5:

How to Remove Mold from Unpainted Drywall

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1
Put on protective gear and seal the area. Mold spores can spread easily, so it’s important to protect yourself and the rest of your house. Wear PPE (personal protective equipment) like an N95 mask, long rubber gloves, safety goggles, and if possible, a full body protective suit. Seal the room from the rest of the house and cover the floor and surrounding area with a plastic sheet.^{[10]
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- Try to work in a well-ventilated area by opening windows and doors. Consider using a HEPA air filtration system to capture airborne mold spores.
- In most cases, if the mold is on the drywall itself, it won’t be enough just to clean the area. It’s better to replace the affected drywall altogether, as the mold has likely spread to the back of the drywall, as well.
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Find a stud and cut a square around the moldy area. Use a stud finder to locate the studs around the moldy area, then mark their location with a pencil so you know where to place the screws when you replace the drywall. Then, use a utility knife to cut out a square of the moldy drywall—this square should be 5-6 inches (12-15 cm) larger than the stain itself and should extend over at least two wooden wall beams behind the drywall.^{[11]
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- Removing more drywall than necessary will increase your odds of removing unseen mold spores and will make it possible to replace the section of drywall.
- If it helps, outline the sections you plan to remove with a pencil, then saw along the lines with your knife. Point it out and away from you as you work.
- When the patch of drywall comes free, carefully remove it and set it down, mold-side up, on the plastic sheet.
- Do not use a saw to remove the drywall, as they can agitate the mold and can be dangerous if used near an outlet.
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Treat the area with a mold-resistant primer. Check behind the drywall you removed to see if the mold has spread to the studs or elsewhere, and remove more drywall as necessary. Then, clean the surrounding area with a mold-killing solution of your choice (bleach, vinegar, or a commercial mold remover) and treat the area with a mold and mildew primer like Kilz to prevent future growth. Let the area dry completely before moving on to the next step.^{[12]
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- If you fit a new piece of drywall when the area is still damp, more mold may grow from the moisture.
- If the moldy area is by a door or window, have someone spray water on the door or window with a hose while the inner wall is open. This will help you locate leaks so you can seal them and prevent future mold growth.
- If there is a lot of hidden mold or the mold is growing on wood, it’s better to hire a professional to inspect the whole area.
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Cut and fit a new piece of drywall. Use a utility knife to cut a new piece of drywall that fits the area you cut out. Place the new drywall in the hole—it should fit snugly—and secure it by attaching drywall screws to the studs you marked earlier. Apply joint compound along the joints, allow it to dry for at least 24 hours, then use a sander or sandpaper to smooth it out.^{[13]
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- If the drywall you removed didn’t come off in one piece, use a tape measure to measure the hole in the wall and cut the new piece of drywall to those exact measurements.
- Kapur says, “It’s just not practical to try to save [moldy sheetrock] in any way. Just cut it off, throw it away, and put in new sheetrock.”^{[14]
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  Expert Source
  
  Mike Kapur
  Certified Mold Assessor & Home Inspector, Sonic Home Inspections
  
  Expert Interview. 19 August 2020.}
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Vacuum the entire area with a HEPA vacuum. Removing and replacing the drywall likely stirred up mold spores, which could have landed on the surrounding walls or flooring. First, dispose of any moldy materials in a garbage bag. Then, use a HEPA vacuum to clean the room and reduce the remaining spores. Properly dispose of the contents in the canister when you’re done.^{[15]
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- Be sure to clean any tools you used to prevent mold from spreading to other parts of your home. It’s usually best to throw PPE materials away.

Section 4 of 5:

How to Prevent Mold on Drywall

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Use a dehumidifier to control humidity levels. In general, try to keep the humidity level in your home between 30% and 50% to prevent mold growth. In addition to using a dehumidifier, keep your bathrooms, kitchen, and laundry room properly ventilated, and use exhaust fans when cooking or showering to remove excess moisture.^{[16]
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- Kapur says, “Another thing that mold hates is any kind of air movement. The dehumidifier does that, as well, because it constantly takes [in] air and then spews it out.”^{[17]
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  Expert Source
  
  Mike Kapur
  Certified Mold Assessor & Home Inspector, Sonic Home Inspections
  
  Expert Interview. 19 August 2020.}
Repair any leaks in plumbing, roofing, or windows as soon as possible. Make sure there’s proper drainage around your home’s foundation, and use waterproof sealants in bathrooms and other damp areas. Try to use moisture-resistant materials in high-risk areas, like basements.^{[18]
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Inspect your home regularly and perform proper maintenance. Routinely check areas that are prone to moisture (like basements, attics, and bathrooms), and look for signs of water damage or discoloration on walls and ceilings. Clean and maintain your gutters and downspouts to prevent water build-up, and consider getting a professional mold inspection annually, especially if you live in a humid climate.^{[19]
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- Kapur says, “Wherever there’s water, mold [and] mildew will grow there. The best way to [prevent mold] is to keep [things] dry. Don't [leave] water standing, and [use] household cleaners.”^{[20]
  X
  Expert Source
  
  Mike Kapur
  Certified Mold Assessor & Home Inspector, Sonic Home Inspections
  
  Expert Interview. 19 August 2020.}

Section 5 of 5:

When to Call a Professional

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Hire a professional if the moldy area is larger than 10 ft (3 m). There are lots of reasons to consider hiring a professional to handle moldy drywall, but the EPA specifically recommends calling a pro if the mold-affected area exceeds 10 square feet. If you begin cleaning the mold and notice it’s spread to the back of the drywall, it’s a good idea to call a professional to inspect how far it’s spread. Here are some other reasons to consider hiring a professional:^{[21]
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- You suspect there’s mold hidden in wall cavities or HVAC systems
- The building has a history of flooding or extensive water damage
- You or your family experience mold-related health issues
- The mold keeps returning after DIY removal attempts
- Be aware that mold remediation can cost $5,000 on average depending on the extent of the damage. If it’s only a small problem, it may be worth attempting to tackle yourself.

Join the Discussion...

How do I safely kill mold?

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WikiCheetahRunner104

I think I found some mold in my bathroom recently and am a little worried. I know mold isn't good and stuff like black mold can be pretty dangero... Read More

Mike Kapur
Certified Mold Assessor & Home Inspector, Sonic Home Inspections

You can use vinegar, diluted bleach, ammonia, or pretty much any household cleaners that have some kind of moldicide in them. If you have mold in... Read More

WikiAxolotlDancer711

I agree that household white vinegar is the way to go! Make sure to give it time to soak if you want to maximize the effectiveness of the vinegar... Read More

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How do you kill mold inside drywall?

Mike Kapur
Certified Mold Assessor & Home Inspector
Mike Kapur is a home inspector and the owner of Sonic Home Inspections, a home inspection company in Westchester, New York. With over 15 years of experience in pre-inspecting properties, Mike specializes in mold, radon, asbestos, lead, water, and air quality testing as well as hazardous materials, pest, infrared, and general home inspections. Prior to founding Sonic Home Inspections, Mike worked pre-inspecting apartments. Mike holds a BS in Accounting from Queens College and is a Certified Mold Assessor in the state of New York.

Mike Kapur

Certified Mold Assessor & Home Inspector

Expert Answer

Unfortunately, you won't be able to fully remove all the mold once it has gotten into drywall. I recommend. you cut out the stained area along with a margin of 5 to 6 inches. Then, just replace the area with a new sheet of drywall.

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What if the mold is inside the walls and I can't see it?

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It very well may be. Scrubbing the mold is not good advice. It spreads the mold spores, and if you are using bleach, will not eliminate all of the mold. The water used will actually make the mold worse. The drywall needs to be carefully removed and disposed of and all of the areas behind the wall must be treated or removed.

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What are the health hazards of living with mold behind the walls?

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You can develop respiratory issues and chronic headaches. It can be very dangerous for athsmatics and young children.

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Drywall mold can affect any home, regardless of age or location. This is why it’s important to inspect your home for water damage regularly.

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If you see or smell mold, don’t worry about trying to determine what type it is. Instead, focus on removing it as soon as possible.

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Warnings

Always wear protective gear when removing mold. Use a disposable dust mask to prevent yourself from breathing in too many of the mold spores. Wear safety goggles and household rubber gloves to protect your eyes and skin from both the mold and any chemicals you use to remove it.

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Seek professional help for problems you cannot address on your own. Black mold is especially toxic and should be handled by professionals.

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