How to troubleshoot mold on interior walls

How to troubleshoot mold on interior walls

Deane Biermeier is an expert contractor with nearly 30 years of experience in all types of home repair, maintenance, and remodeling. He is a certified lead carpenter and also holds a certification from the EPA. Deane is a member of The Spruce's Home Improvement Review Board.

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  • Working Time: 8 – 10 hrs
  • Total Time: 1 – 2 wks
  • Yield: 10 feet by 10 feet
  • Skill Level: Intermediate
  • Estimated Cost: $200 to $500

Mold inside your walls is a sure sign of moisture intrusion. Mold also leads to the deterioration of insulation, studs, and drywall. Some types of mold can be hazardous to your health. And for anyone thinking of selling their home, mold in the walls will undoubtedly show up on the inspection report.

Mold remediation in walls is a relatively simple, though messy, project that can stretch for a week or two. Because of this and because of safety concerns, many do-it-yourselfers decide to hire a professional mold remediation company.

7 Common Signs Mold Is Inside Your Walls

Musty Smell

Mold has a musty smell often compared to wet cardboard, wet pets, or an old house’s basement.

Visible Mold

Mold inside walls often stays within the walls. But when it does migrate to the drywall paper, wallpaper, paint, or baseboards, it appears in patchy clusters of small spots. Mold can be black, white, gray-green, or gray-brown.


Walls might be temporarily damp from the use of a shower or from cooking. But if they are permanently damp and there is no apparent moisture source from within the room, it's likely that the drywall, insulation, or studs inside are wet.

Soft Drywall

If the drywall is mushy, flakes away, or indents under your touch, it is probably wet. If the drywall is wet, it will most likely be moldy, too.


Dark stains on walls usually indicate previous or current dampness within the walls.

Previous Flooding

If flooded water has come into contact with the walls, it’s almost certain that mold is growing in the walls.

Poor Health

Not all mold is toxic and not all people are susceptible to the effects of mold spores, though they can lead to various negative health effects.

How to Check for Mold Inside Your Walls

  1. Locate the center of the area most likely to have mold inside.
  2. Shut off power to the area at the electric service panel.
  3. With a pencil and straightedge, lightly mark a square approximately 6 inches by 6 inches.
  4. Cut along the outline with a drywall jab saw.
  5. Remove the cut-out and inspect its back for mold.
  6. If there is no insulation in the wall, look at the back wall. Also, hold a small mirror inside and shine a flashlight on the mirror to inspect the back of the drywall.
  7. If there is insulation, any mold on the drywall or studs will have spread to the insulation. So, the presence of mold on insulation usually means mold on other building materials.

When to Remove Mold From Inside Walls

Unlike some other types of deterioration around the home, there is no acceptable level of mold in your walls and no waiting period. Once you discover mold, it's best to open up the walls and remove the mold as soon as possible.

Mold can spread and affect other areas of the walls, insulation, ceiling, flooring, studs, and joists. The longer you wait to remove the mold, the longer mold has to grow.

Identifying and fixing the source of moisture in the walls is a necessary component of removing mold. Common sources include leaking ceilings, elevated indoor humidity, indoor condensation, and outdoor leakage from gutters or drainpipes.

Before You Begin

Removing mold from inside walls is a four-step process: removing moldy drywall and other materials; killing mold; encapsulating remaining mold; and rebuilding part or all of the wall with new drywall, insulation, and other building materials.

  • Removal/Disposal: Moldy drywall and insulation must be removed. None can be reused.
  • Kill Mold: Spray the mold with a liquid biocide to kill it. Alternatively, exposing the mold to air and light for long enough will kill it. Do not use household bleach.
  • Encapsulate Mold: Cover the mold with a fungicidal mold encapsulant. Choose a coating that contains the active ingredient calcium hydroxide. Do not use ordinary house paint.
  • Rebuild: The area must be rebuilt with new building materials. New insulation is added to exterior walls (interior walls do not require this). Drywall is hung, then painted. For areas with persistent mold, you may even choose mold-resistant drywall.

Citing environmental concerns, the EPA's position on mold biocides is that they are permitted but not recommended. The EPA makes an exception for areas where immune-compromised individuals live. The EPA does not ban biocides. Instead, it recommends that the mold be killed with ventilation and light.

Safety Considerations

Wear NIOSH-approved breathing protection, disposable gloves, and coveralls or old clothing that you can wash at the end of each day. Double-bag the moldy debris in large plastic contractor clean-up bags. Avoid carrying the bags through the house; drop them out of windows if possible. If your area regulates the disposal of moldy debris, do not place the bags in the regular municipal trash run. Instead, check with your city for transfer stations designated for this type of trash.

Mold in walls is a particularly tricky problem. It can grow there for quite some time before you even realize it’s there, spreading unseen inside the walls. The mold in your walls may not stay in the walls, either. It can spread throughout your home. And even if you’re not aware of its presence, mold inside walls can cause health problems.  

How Do You Know if There is Mold in Walls?

If you’ve had significant water damage, like a broken pipe inside a wall or flooding in your home, there is a possibility of mold growing within the walls. In such cases, you’re going to need to remove and replace the drywall anyway, so while you’re at it, it’s easy enough to check for mold inside the walls.

If you see mold on the surface of a wall, it is possible there is mold inside the walls, as well. Because it is difficult or impossible to remove mold from porous materials like drywall, you will need to remove and replace the moldy section of drywall. That will make it easy to check for mold inside the wall. Use a small mirror with a long handle and a flashlight to look inside the walls for mold.

Yet another sign of mold growing unseen inside the walls is a musty odor. There are other, easier places to search for hidden mold if you smell that characteristic musty odor that indicates mold is present somewhere, but if you’ve looked elsewhere and can’t find it, you may need to check inside the walls.

If you’re not sure whether or not you need to check inside the walls, you can consult with a mold removal professional for advice.

How Do You Check for Mold inside Your Walls?

To check inside your walls for mold, you’ll need to carefully cut out six-inch squares of drywall, remove the cut-out squares, and use a long-handled mirror and flashlight to look inside for mold. It is recommended that you check in several places, since you might miss small amounts of mold if you only look inside the wall in one spot. The U.S. Environmental Protection Agency (EPA) recommends hiring a professional to help you look for hidden mold, including mold in walls, since the process can potentially spread mold throughout the room and expose you to harmful mold spores, if in fact it turns out there is mold inside the wall.

How to troubleshoot mold on interior walls

Mold in walls found under sheetrock

How Do You Remove Mold Inside Walls?

Before attempting to remove mold in walls remember that these procedures are to be performed inside a contained area while wearing personal protective equipment and operating negative air filtration equipment.

If mold is growing on the back of drywall, the drywall must be removed and replaced. Any insulation in the wall should be removed and replaced. Moldy materials should be double bagged in heavy plastic trash bags before you carry them through the house for disposal, to prevent the inadvertent spread of mold throughout the home in the process.

After sheetrock walls and/or ceilings are removed, the exposed studs and joists and the surfaces between the studs and joists need to be HEPA vacuumed to remove all of the settled dust deposits from these surfaces, as these deposits are likely to contain elevated levels of mold and bacteria. The same holds true for floor joists when wood floors are removed during a mold remediation project.

After the HEPA vacuuming work is performed, studs, joist, and surfaces in between need to be disinfected. Any cleaning product that contains an anti-microbial substance is adequate to disinfect these surfaces. Foster 40-80 is an excellent product, which we recommend. Metal studs and sills can be wiped with a cloth or paper towels dampened with the product. For large areas, you can use a one-gallon garden-type pump sprayer containing the disinfectant and spray the surfaces. Masonry surfaces, such as concrete, bricks, tiles, cinder blocks, etc, and wood and vinyl floors are also disinfected with disinfectants when masonry materials are associated with a mold remediation project or are located inside a contained work area.

After surfaces are disinfected and dry, any wood surfaces displaying residual mold should be encapsulated with an encapsulant coating. Encapsulant coatings are similar to paints, but they contain chemicals that have fungicidal properties, which kill mold. Additionally, when the encapsulant paint dries, the coating hardens and locks down any mold onto the surface of the wood so that mold spores cannot become airborne. Remember, dead or alive, mold is equally allergenic, so it is important to encapsulate any residual mold. Encapsulant coatings are used on wood, provided that the wood is not wet. Otherwise, you have to wait until the wood is dry before using the coating. The encapsulants can be applied to wood surfaces using a brush or a roller. For large areas of wood containing residual mold, high-pressure airless sprayers are used, but these sprayers are expensive to purchase. A popular and effective encapsulant is Caliwel paint, which contains calcium hydroxide, a chemical that gives the paint anti-fungal (fungicidal) properties. Surfaces to be encapsulated must first be primed with Caliwel primer before being encapsulated. Another common encapsulant is Foster 40-50, which is white, and Foster 40-51, which is clear. Both the Caliwel product and the Foster products can be applied with a brush, roller, or high- pressure, airless sprayer.

For Help Removing Mold in Walls

If you need help removing mold in your walls, or if you’d just like some advice about the mold removal process, we suggest scheduling a free consultation in your home with a mold removal professional. There’s no obligation on your part, so even if you opt to handle the mold removal job yourself, you can benefit from some free professional guidance. To find qualified mold removal professionals offering free consultations in your area, you can follow the link.

In addition to getting rid of the mold, you need to figure out why it appeared and how to keep it from coming back

Q: How can I clean mold off walls?

A: Your question prompts many more. How much mold are you dealing with? Is it just on the paint or tile, or is it embedded in drywall? Do you have any underlying health issues that warrant extra caution? And do you know why the mold has appeared and what to do to keep it from returning?

Get the full experience. Choose your plan ArrowRight

Much has been written about serious mold problems and the health consequences. These concerns are valid. But it’s also important to keep things in perspective. You probably don’t need a hazmat team to come in to clean a one-square-foot patch of mold off a wall.

The Environmental Protection Agency suggests about 10 square feet — about 3 by 3 feet — as a gauge for determining what homeowners can probably clean up themselves with basic safety measures vs. what needs professional-level protocols, whether by the homeowners or by a professional remediation team. This threshold was set because of an understanding of what makes mold — and mold cleanup — a risky endeavor from a health standpoint. Mold and mold spores are allergenic, and some molds are toxic. This is true whether the mold or the spores are dead or alive, which is why the EPA does not generally recommend using chlorine bleach or other biocides as part of mold cleanup. The chemicals pose their own health risks without a health benefit.

Paint companies, which often recommend scrubbing away mold with a solution of bleach in water, have a different perspective. Their interest is in making sure a new coat of paint sticks and doesn’t immediately start growing mold or mildew. So they recommend using bleach as a way to sanitize the surface, although what’s not usually stated is that, unless the new paint goes on as soon as the wash water dries, it won’t necessarily guarantee that new, live spores haven’t taken up housekeeping on the surface in the interim.

Whether you include bleach or other biocides as part of your routine, it’s important to recognize that mold can cause allergies if you get it on your skin or in your eyes, or if you inhale the spores. To clean up even small areas, the EPA recommends wearing rubber gloves, goggles and a mask labeled as an N95 respirator.

If the mold is on a hard surface, which includes paint on a wall, use a cloth or sponge dampened with water, or water mixed with a little detergent, to wipe it off. Rinse out the cloth or sponge and wipe again.

If the surface is stained and will stand up to bleach, or if you plan to repaint and are following instructions from the paint manufacturer, wipe the cleaned surface with a diluted bleach solution. Use 1 part bleach to 3 parts water, according to Sherwin-Williams. If you don’t want to use bleach but do want something other than water, try vinegar, borax or branded products that you can find at a hardware store or home center, which also kill mold. Even if you do sterilize the surface, though, enough mold spores are always floating around in the air that mold can regrow if the conditions are right.

If the mold is on a porous surface, such as ceiling tiles or unpainted drywall, there is no way to completely get rid of it. You will need to remove and replace the moldy material. Besides making this a much more complicated job, removing contaminated material also greatly increases the risk of stirring up mold. Switch off and seal vents for heating and air conditioning, and try to create negative air pressure in the room. Pros do this by taping up plastic sheeting and setting up an exhaust fan to pull room air out through a window.

For a relatively small job in a small room, you might just clear out the room (so you don’t have to decontaminate everything later), close the door and switch on a box fan in a window. Tape up cardboard to seal around the fan, so fresh air doesn’t come in from the window; you want the fan to be pulling air from the rest of the house through gaps around the door, ensuring that air in the room doesn’t get into the rest of the house. Wear clothes you can toss, and bundle up all the debris before you open the door.

Whether the mold is on porous or nonporous surfaces, probably the most important aspect of cleanup is preventing the mold from reappearing. One of the key conditions that allows mold to flourish is moisture, which can form on surfaces because of a water leak or because of condensation from warm, humid air hitting a cold surface. If there is a leak, you need to fix it. The remedy for condensation, though, isn’t always as obvious. If the mold grew on a wall in a closet in a cold corner of your house, try increasing ventilation by clearing out clutter and leaving the door slightly ajar. Desiccants can also be helpful.

If the mold is on a bathroom wall, consider upgrading your exhaust fan — and make sure it vents to the outdoors, not the attic. To boost airflow to get shower steam out of the room, try leaving the door slightly open while you shower. And consider adding a timer switch to the fan, so it stays on for about five minutes after your shower ends. Wiping down shower walls can also help lower the amount of moisture in the room; use a squeegee or a microfiber cloth that you can wring out.

A damp basement or crawl space can lead to mold problems throughout a house, not just under the floor, because of the way air and water vapor move. A dehumidifier can help, or you may need to install a basement waterproofing system or cover the dirt in a crawl space with plastic. This Old House has a good overview in an article titled “Wet Basement Solutions: How to Stop the Leaks From Coming” on

Especially in a bathroom, where moisture is always an issue, it can be helpful to repaint with a product formulated to resist mold or mildew growth on the paint surface. Sherwin-Williams, for example, includes antimicrobial ingredients in its Emerald, Duration and Harmony lines. As extra insurance, you might want to prime first with Zinsser Mold Killing Primer ($14.99 a quart at Ace Hardware), which is registered as a fungicide and can kill spores on the surface, negating the need to wash first with a bleach solution.

If you notice mold on a drywall surface in your home, try not to panic. The truth is that mold can happen anywhere and in any home. All it needs to grow is a source of moisture and an organic food source, and drywall can be an all-you-can-eat buffet. Read these steps on how to safely remove mold from your drywall.

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Mold spores are everywhere. They float through the air and can settle on any surface. If that surface is damp and there’s a food source present, mold will grow.

The paper face on a damp sheet of drywall can be the perfect food source for a spore to dig into. Before long, the mold can multiply and spread across the entire wall and into the wall cavity, feeding on wood framing and flooring.

While it’s hard not to panic at the thought of a mold problem, you can handle most drywall mold scenarios on your own. According to the EPA, homeowners can remove mold on drywall under 10 square feet. Larger infestations might require a pro.

Steps for Removing Mold from Drywall

The following are some steps you can take to remove mold from drywall.

1. Stop the Source of Moisture

Before you start removing the mold from your drywall, you have to stop the source of moisture. Whether it’s a leaky window or pipe, a roofing issue, or water vapor weeping through a concrete floor, you have to fix the problem. Otherwise, mold will start growing almost immediately after you finish removing it.

2. Gather Your Drywall Mold Removal Equipment

When you remove mold, you’ll undoubtedly stir up spores and send them airborne. Wearing long sleeves and pants, as well as rubber gloves, a respirator mask, and a pair of safety glasses will help keep those spores from irritating you.

4 Types of Whole House Air Filters

To help minimize the number of spores in the air, use a vacuum fitted with a HEPA filter to remove surface spores. It’s also a good idea to block the rest of the home off with plastic sheeting and run a negative-pressure HEPA air filtration system, which you can rent from most tool rental shops.

Other materials you’ll need:

3. Decision Time: Save or Scrap?

There are times when removing moldy drywall is safer, more effective, and less time consuming than cleaning it. If your drywall surface is soft to the touch, the moisture and the mold have taken their toll on its structural integrity. In this case, it’s better to remove the drywall, kill the mold on the framing underneath, allow it to dry, and start fresh.

4. Remove Surface Mold from the Drywall

If you decide to remove the mold from your drywall yourself, you’ll need to handle the surface spores first. Vacuum the entire surface with your HEPA-equipped shop vacuum. Use a brush attachment to ensure you’re breaking up the spores and removing as many as possible.

5. Kill the Mold

With most of the surface spores removed, you can start killing the mold. There are a few different products that you can use for this step:

Contrary to popular belief, bleach is not always effective for killing mold. It can kill the surface spores but won’t do much to attack the roots.

Spray or brush your solution on your drywall and allow it to sit for 10 minutes before brushing the surface in a circular motion with a medium-bristled brush.

If you’re using Concorbium, you want to wait until the surface is dry, then dampen the brush with a bit more Concorbium before you start brushing.

A quick cleaning with a household cleaning wipe should remove any residue that might remain after brushing.

6. Use a Fan to Dry the Wall

With the spores killed and residue removed, the next step is to let the wall dry. Set up a box fan and point it directly at the wall. Allow it to run for 24 hours to ensure that the wall dries completely.

7. Cover the Stains

After 24 hours, you might notice some discoloration on your drywall. Most of the time, this discoloration is simply an easily handled stain, not mold reforming. To be sure, you can use a mold-killing primer like this product from Zinsser. These primers create a fungicidal protective coating that can cover the stains while also killing any rogue spores.

Once the stains are no longer visible, you can paint over the surface with mold-resistant paint like these products from JH Wall Paints. These paints’ alkaline pH levels create an inhospitable environment for molds and bacteria.

8. Keep the Humidity Low

A humid environment can encourage mold regrowth in the future. Do your best to keep the space dry and mold-free by minimizing the humidity levels. Use a dehumidifier to keep the humidity between 30 and 50 percent to deter mold from growing in other areas.

Following these steps will help you remove mold from your drywall surfaces and discourage it from growing back.

Flood water may contain bacteria, petroleum and chemicals. Mold can grow in a flooded home that is not properly cleaned and dried out.

Learn how to safely clean your home after a flood:

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Mold (mildew), mushrooms, and yeast are all types of fungi. Fungi are found both indoors and outdoors. Hundreds of different kinds of mold are commonly found in the United States and New York City.

Exposure to mold can cause or worsen asthma symptoms and allergies, such as hay fever. People who are allergic or sensitive to mold may experience congestion, runny nose, coughing and trouble breathing.

Some people are at risk for more severe reactions to mold, such as fever and shortness of breath. This includes people who are exposed to large amounts of mold at work such as, agricultural workers and building demolition workers. People who have had or are undergoing certain medical procedures, such as bone marrow or organ transplants and chemotherapy, are also at risk. Health symptoms usually disappear after the mold has been removed.

Identifying Mold

Mold can be different colors, including gray, black, green, yellow and orange. It may look furry, slimy or powdery. Some mold has a musty, stale or earthy smell.

Mold usually grows in wet or damp places. It can grow on paper, fabric, wallpaper glue, sheetrock, wood, soap scum, leather and other surfaces. It can grow where there is water, high humidity or damp conditions. Mold grows faster in warm temperatures and high humidity.

Exposure to Mold

You can breathe in mold particles if mold is disturbed or damaged. You can also breathe in tiny spores (similar to seeds) that mold may release into the air. Mold can get on your skin if you touch it. You can swallow mold if you eat moldy or spoiled food. If you think that you have symptoms related to mold exposure, you should see a health care provider.

Mold Prevention and Removal

The best way to prevent mold is to remove water and moisture sources. Fix leaks, dry damp areas and remove humidity from the air to help stop mold growth and keep it from coming back.

  1. Seal off moldy areas using a plastic sheet and duct tape until cleaned. Keep children and pets away.
  2. Use water and soap to clean small areas of mold on walls or other hard surfaces when you see it. Wear waterproof gloves while cleaning.
  3. Dry the cleaned area completely.
  4. Clean any visible dust from work areas. Use wet mops or HEPA vacuums.
  5. Throw away all cleaning-related waste in heavy-duty plastic bags and seal securely.

If the mold returns quickly or spreads, there may be an underlying problem, such as a water leak. Report repeated mold problems to your landlord.

If large areas of mold are present, you may need outside help such as a professional mold abatement company. Be sure your contractor is licensed and follows NYS Labor Law requirements.

Building Requirements

Landlords of buildings with three or more apartments, or buildings of any size where a tenant has asthma, are required to keep tenants’ homes free of mold. This includes safely repairing water leaks and correcting persistently high humidity levels.

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Guidance on the causes of condensation and black mould.

There is a difference between damp and condensation in your property and how it is caused.

Condensation is dampness formed when air containing water vapour is cooled by contact with a cold surface.

Why – warm air inside buildings is capable of holding varying amounts of moisture. When warm, moist air touches a cold surface, such as a window or external wall, it is then no longer able to hold as much water vapour. The air-borne moisture then turns into drops of water and collects on the cold surface. This is called condensation.

Condensation is caused by day-to-day activities, coupled with lack of ventilation and background warmth.

The average household produces around 14 litres or 24 pints of water vapour every day. This vapour is held in the warm air and must be allowed out of the property, otherwise condensation may form. The main sources of water vapour are:

  • Drying clothes
  • Cooking
  • Boiling Kettles
  • Bathing/showering
  • Unvented dryers
  • Washing machines

Condensation is different from damp. It is surface dampness and can be visible as black mould. It mainly occurs on cold walls inside and other cold surfaces such as tiles and cold-water supply pipes under sinks and hand basins. Condensation is usually worse during the winter.

Are you sure it is condensation?

Some forms of damp are caused by leaking pipes, a leaking roof or rising damp. Leaks often result in patches of damp coming through the plaster and wallpaper near where the leak is. Rising damp can be identified by a damp ‘tidemark’ low down on the inside walls.

Black mould

Small amounts of condensation can be found in most homes, but if you do not deal with it, and it is allowed to get worse, then black mould growth can occur. This can form on walls, surfaces personal possessions.

Black mould is almost exclusively caused by condensation and is usually found at the skirting level in rooms, in the corners of walls and ceilings or on cold surfaces. Mould can also appear on cold surfaces such as tiles and window sills or behind furniture where the air flow is restricted. Mould and mildew can also grow on furnishings, curtains and even clothes and shoes and can spoil wallpaper and furnishings.

Some damage may be permanent. JRHT will not pay for black mould damage to your personal possessions caused by condensation. You should check if you can claim this back from you home contents insurance.

Dealing with mould growth

If you see black mould, this can be removed by wiping down with detergents or proprietary mould removers. It can be washed out of fabrics but may leave stains or spoil colours.

The best way of tackling mould is to reduce the condensation levels and prevent it growing in the first place.

What can you do to prevent condensation?

It is your responsibility to prevent and address condensation in your home.

The amount of condensation depends on how much water vapour is in the air. Many everyday activities add to the water vapour level in your home, but their effect can be kept to a minimum.

Cover pans when you’re cooking

Keep the bathroom door shut and the room well ventilated.

When filling your bath, run the cold water first then add the hot – it will reduce steam by 90%

Hang washing outside to dry whenever you can.

If you must use a tumble dryer make sure it’s vented to the outside.

If you must dry washing indoors use the bathroom and keep the door shut and the room well ventilated

Do not hang wet washing on radiators all round your home – doing so is very likely to cause condensation problems

It is important to let air circulate around your home. To reduce the presence of mould on clothes or other stored items, do not store shoes etc underneath cabinets, pull furniture slightly away from walls, keep wardrobe doors and drawers slightly ajar, pull shelves away from the back of wardrobes, do not over fill rooms, cupboards or shelves or display cabinets.

Avoid cluttering rooms with personal possessions – too many personal items prevents air form circulating freely around your home and can cause condensation

Condensation can be a problem if it is not dealt with – it is your responsibility as a resident to take action to prevent excessive condensation in your home. If after having read this, you require further information please contact us on 0800 5870211.

When black mold is growing, it is usually necessary to focus on treatment of black mold inside walls, and this process can be quite difficult if you don’t understand the steps to completely get rid of the mold. This article will help you to learn how to remove black mold from wall materials such as sheetrock, tile, insulation, wooden studs and paint.

Even though your first inclination may be to treat the problem on your own, it is important to consider the health implications of an insufficient cleanup. Mold spores are small and they can quickly spread, and when the treatment of black mold inside walls is not handled correctly it can result in exposure to your family and continued mold growth even when you think the problem has been solved.

Mold Growth Within the Walls

Even if the mold problem does not seem serious, water stains can indicate a need for treatment of black mold inside walls. In fact, you may not see signs of mold on the outside of the wall, but the inner wall may be growing mold spores that can be spread throughout the house. When you learn how to remove black mold from wall areas, proper procedures need to be followed in order to prevent cross contamination when the wall is opened up.

The cleanup process usually begins by removing the wall covering, such as drywall or sheetrock in order to view the damage within the wall. Remember, that porous materials such as sheetrock and insulation should be replaced. Even though the sheetrock may appear to be OK, it is likely that mold spores are still present and the mold may continue to grow even if you follow a treatment of black mold inside walls. The exposed sheetrock should be discarded and replaced with new material.

Also, some people want to learn how to remove black mold from wall insulation, but this process is not possible because of the fact that the insulation can hold many mold spores. Don’t try to reuse insulation, it is better to purchase new insulation to avoid future problems.

Avoiding Future Mold Problems

When the wall is open, it is necessary to find the source of the water leak in order to stop the moisture that is accumulating within the wall. Also, be sure to completely dry the area before closing it back up, because even a slight amount of moisture can result in mold growth.

The wall studs should be replaced if possible. If they can’t be replaced the studs should be cleaned as best as you can, and then encapsulated. Be sure that you are wearing protective goggles and a mask, and seal off the room so that mold spores do not travel through the rest of the building. Professional sometimes will sand down moldy wood to get to all of the mold, but that is too dangerous of a job for the average homeowner.

It is possible to do-it-yourself if you have black mold inside walls, but a better option is to call a professional to take care of the problem for you. Mold specialists are familiar with how to remove black mold from wall materials, and they will be able to handle any situation that they find within the walls.

A professional company has all of the equipment that is needed to clean up the mess, and they will be able to do it quickly in order to reduce the amount of time that your family is exposed to mold. Using a specialist is safer for your family, and it will give you peace of mind to know that you don’t need to worry about mold problems in the future.

How to troubleshoot mold on interior walls

Black mold has become a buzzword in house buying and selling, and it is undoubtedly a cause for concern if the mold in question is Stachybotrys, which has the highest toxicity. However, the fact is that all kinds of mold are everywhere, both inside and outside your house. The real problem is when mold levels are more concentrated inside than outside.

Often gray, white, green or black in appearance, mold in your house is most commonly found in damp, poorly ventilated, and warm places such as bathrooms, basements, kitchens, and laundry rooms. And whether or not it poses a high level of toxicity, you still don’t want it on your walls. In this post, we will discuss how to remove mold from walls.

When to Consult a Mold Remediation Expert

Most types of mold spores multiply within 48 to 72 hours of moisture, and black mold becomes more of a possibility the longer water damage remains, usually after 7 to 10 days. So, if you have an area that has been damp or wet for a period of more than a few days, it’s best to consult with an expert in mold remediation for professional services. You should also call mold remediation experts if the mold covers areas of 10 square feet or more, if it is in hard to reach places or reappears after your cleaning efforts.

Important Things to Know BEFORE Removing Mold from Walls

  1. Always start by identifying the source of the water intrusion and make sure it is stopped before attempting to remove mold; otherwise, the spores are likely to return.
  2. Always wear protective suits, masks, gloves, and eyewear to ensure your safety.
  3. Air filtration devices equipped with HEPA (High Efficiency Particulate Air) filters should be used to direct air outside to create a negative pressure environment and ensure that contaminants are not transferred through the air during removal. Close air vents and turn off your HVAC system, too, if possible.
  4. Rags, towels, gloves, and any other materials used for mold removal should be put in sealed plastic bags before being taken away from the affected area and discarded.
  5. Moldy drywall should be removed two feet beyond the visible mold spores.
  6. Cleaning the mold remediation area should be done with a disinfecting agent containing quaternary ammonium chloride and a HEPA-vacuum.
  7. Keep immuno-compromised people out of the containment area.

Mold remediation projects can be very complicated, requiring careful planning and painstaking work, so it’s best to call an expert like Hays + Sons.

That said, if you still feel comfortable enough, here are some things you can do yourself to remove mold on your walls, provided you have eliminated the water source.

How to Remove Mold from Painted Walls

If the mold is on the surface of painted walls, it is generally easier to clean. Follow these steps to remove mold off your painted wall:

  1. First move everything away from the area and off the wall so you aren’t simply moving the spores to another area. Put plastic on the floor to protect it.
  2. Use warm water and dish liquid containing a surfactant (such as Dawn dish soap) to moisten a huck towel or cotton rag and remove dirt and debris. This won’t kill the mold, but it will make it easier to remove the mold in the next step.
  3. Get a mold cleaner from your home improvement store, or use a bleach solution containing one part bleach and three parts water.
  4. Spray the affected area, scrub and wipe clean. Then spray again, let it sit for 10 minutes, wipe (with a different side of your rag or towel to avoid re-contamination), then rinse and dry the wall.
  5. If you have scrubbed any paint off, you will need to repaint. It’s recommended that you paint with mold-inhibiting paint. Just make sure you thoroughly dry your wall before painting!

How to Remove Mold from Bare Drywall

If you spot mold on your drywall, it may indicate a larger mold problem in the stud space behind the drywall. And, mold on drywall has already penetrated the surface, so you can’t simply wipe it clean. You will need to cut it out and replace it in this case. Follow these steps:

  1. As with the painted walls, you will want to move everything away from the area and use plastic on the floor to protect it.
  2. You’ll need something to attach the new piece of drywall to, so use a stud finder to locate the wooden supports behind the wall.
  3. Mark the area you plan to cut with a pencil and straight edge, making sure to mark a space two feet larger than the visible mold to make sure you get any mold you yet can’t see as well.
  4. Use a utility knife to cut out the section you marked. Do not use a power saw, as this can agitate the mold and cause the spores to get into the air.
  5. To limit spread of mold spores, carefully remove the drywall piece and place it mold side up on the plastic.
  6. Clean the cavity with mold cleaner to make sure you’ve gotten it all, and dry it thoroughly.
  7. You will want to make sure your new piece of drywall is the same size as the one you cut out, so measure the length and width of the missing section of drywall and cut the new section to those measurements.
  8. Attach the new piece of drywall with screws, apply a joint compound to patch seams, let it dry and sand.
  9. Wrap up soiled materials in the plastic and throw it away.
  10. Vacuum the room with a HEPA vacuum.

All said, not wanting to do it yourself is understandable. Mold can be frustratingly difficult to remove and cause health issues. So, if you need help with a mold problem, contact the experienced and dedicated team of certified mold remediation experts at Hays + Sons.

About Hays + Sons

For more than 38 years, Hays + Sons has been the property restoration company that families, businesses and schools trust. We’re committed to helping you be prepared when the unexpected strikes, and whether you just want tips for mold prevention and remediation or currently have mold or water damage that may turn into mold, Hays + Sons has the capacity and expertise to help you get back to normal ASAP.

The compassionate, experienced, and trusted residential restoration experts at Hays + Sons are just a phone call away, 24 hours a day, 7 days a week, 365 days a year.

If you’re in need of mold remediation, get in touch with us at one of our offices across Indiana or in Cincinnati, Ohio.

Whether it’s the slimy black spots on your shower curtain, the fuzzy white patches on your basement floor, or the slick orange film that forms on your kitchen drain, household mold is more than unsightly. In some cases, mold in your home can make you sick, especially if you have allergies or asthma.

Whether or not you’re allergic to molds, mold exposure can irritate your eyes, skin, nose, throat, and lungs. Here’s what you can do to combat mold problems, and take care of yourself and your home.

Mold Reactions: Who’s at Risk?

For people sensitive to mold, inhaling or touching mold spores can cause allergic reactions, including sneezing, runny nose, red eyes, and skin rash. People with serious mold allergies may have more severe reactions, including shortness of breath. In people with asthma who are allergic to mold, breathing in spores can also cause asthma attacks.

In addition to people with allergies and asthma, others who may be more sensitive to the effects of mold include:

  • Infants and children
  • The elderly
  • People whose immune systems are compromised due to HIV infection, cancer, liver disease, or chemotherapy
  • People with chronic lung disease

What Is Mold?

Mold is a type of fungus that consists of small organisms found almost everywhere. They can be black, white, orange, green, or purple. Outdoors, molds play an important role in nature, breaking down dead leaves, plants, and trees. Molds thrive on moisture and reproduce by means of tiny, lightweight spores that travel through the air. You’re exposed to mold every day.

In small amounts, mold spores are usually harmless, but when they land on a damp spot in your home, they can start to grow. When mold is growing on a surface, spores can be released into the air where they can be easily inhaled. If you’re sensitive to mold and inhale a large number of spores, you could experience health problems.

Where Do Molds Grow?

Your walls, floors, appliances, carpet, or furniture – they can all provide the food mold needs to grow. But the thing all molds need most is moisture, so you’re most likely to see mold in damp places such as bathrooms, kitchens, laundry rooms, basements, and crawl spaces.

Top Tips for Controlling Mold

It’s impossible to get rid of all mold and mold spores in your home, but because mold spores can’t grow without moisture, reducing moisture in your home is the best way to prevent or eliminate mold growth. If there is already mold growing in your home, it’s important to clean up the mold and fix the problem causing dampness. If you clean up the mold but don’t fix the problem, the mold will most likely return.

Following is some advice for reducing moisture throughout the home with specific tips for the areas most prone to dampness and mold growth:

Around the house:

  • Use dehumidifiers and air conditioners, especially in hot, humid climates, to reduce moisture in the air.
  • Keep indoor humidity below 60% if possible. You can measure relative humidity with a hygrometer, an inexpensive instrument available at many hardware stores.
  • Keep air conditioning drip pans clean. Make sure drain lines are free of obstructions and flow properly.
  • Keep the house warm in cool weather. As the temperature goes down, the air is less able to hold moisture and it condenses on cold surfaces, which can encourage mold growth.
  • Add insulation to cold surfaces, such as exterior walls, floors, and windows to reduce condensation.
  • Dry wet areas within 24 to 48 hours to prevent mold growth.
  • Fix leaks and seepage. The ground should slope away from your house. If water is entering the house from the outside, your options range from simple landscaping to extensive excavation and waterproofing.
  • Have a heating and cooling contractor check your heating and cooling system to make sure it’s sized and operating properly to remove humidity. If your system is too big or the airflow is incorrect, your air conditioner will not remove humidity like it should. Also, ask the contractor to check your duct system for air leaks, and proper size and air flow to each room.
  • Open doors between rooms to increase circulation, which carries heat to cold surfaces. Increase air circulation by using fans and by moving furniture from wall corners.

In the kitchen:

  • Use exhaust fans to move moisture outside (not into the attic) whenever you are cooking, washing dishes, or cleaning.
  • Turn off certain appliances if you notice moisture on windows and other surfaces.
  • Check for leaks around the kitchen sink, refrigerator ice makers, and other sources of water. Repair if necessary.
  • Empty and clean refrigerator drip pans if necessary.

In basements and crawl spaces:

  • Put a plastic cover over dirt in crawl spaces to prevent moisture from coming in from the ground. If there is standing water or the soil is wet, dry it out with fans before covering the floor.
  • Be sure crawl spaces are well ventilated by using fans and having vents installed in outside walls if necessary.
  • Consider painting concrete floors and using area rugs instead of wall-to-wall carpet in basements. If you plan to install carpet over a concrete floor, it may be necessary to use a vapor barrier (plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem.
  • Have your basement floor checked for leaks and have them repaired if necessary. Water can enter your home by leaking or by seeping through basement floors or walls.
  • Make sure gutters are working properly and that outdoor landscaping causes water to run away from — not toward — the house.
  • Do not finish basement walls with insulation and wall board unless your basement is very dry.

In the laundry room:

  • Vent your clothes dryer to the outside.
  • Make sure the vent is clear of obstructions, such as lint, and that there are no holes that leak air. If the vent duct is damaged, replace it with a metal duct. Have the duct cleaned at least once a year.
  • Avoid leaving damp clothes in the laundry basket or dryer. Wash and dry them promptly.

In bathrooms:

  • Use exhaust fans to remove moisture to the outside (not into the attic).
  • Use area rugs, which can be taken up and washed often instead of wall-to-wall carpeting.
  • Check for leaks around basins and tubs and have them repaired if necessary.
  • Open a window when showering.
  • Avoid leaving damp towels on the floor or in the laundry hamper.

Show Sources

United States Environmental Protection Agency: “A Brief Guide to Mold, Moisture, and Your Home.”

Rhode Island Department of Heath: ”Some Basic Facts About Mold and Mildew.”

When your home has suffered water damage, it’s very likely that your home will also experience mold growth. If the water damage is serious, then within 24 hours, mold can begin to grow on your property after water has soaked through to reach the drywall. If you have pipes in your home that are leaking, they can trap moisture in the walls, resulting in water damage and likely mold growth.

Problems Caused by Mold

How to troubleshoot mold on interior walls

Mold can be as dangerous as it is destructive. Make sure to have it removed as soon as you find it.

Mold growth is particularly concerning because the mold will continue to eat away at affected building materials and increase the damage as it spreads. Mold will also compromise the air quality of your home and pose as a health hazard to any and all occupants. Among some of the health concerns that mold presents are eye irritation, coughing, nasal issues, and throat irritation.

Knowing the amount of damage mold can cause, it is important for you to know how to detect mold in your home. However, it can sometimes be difficult to spot mold because it can be hidden. One case of this is mold growth behind your home’s walls.

Here’s what to look for when finding mold behind the walls:

Discoloration and Stains

Because mold growth is often a result of water damage, water stains can be an indicator of the presence of mold. As such, if you spot water stains on your walls, then it is likely that there’s mold growing behind them. Water stains can be yellow or brown in color, so look out for such colors on your wall. If the spots are damp, then that’s an obvious sign of moisture problems as well.

Another indicator of mold growth is discoloration, which can occur even if you have repainted your home’s walls. Discoloration can also happen in the event that damage has been done from within. This is because the mold will still be visible on the wall’s surface.

Mold can appear in many shades, from black to white to brown to gray to green. If your wall has vinyl wallpaper, mold will look pink, orange, or purple in appearance.

Surface Changes and Deterioration

Your walls’ appearance can change significantly if there’s mold growth behind them. In addition to discoloration and stains, your walls may deteriorate. Paint or wallpaper can crack, peel, or bubble because of moisture and mold growth. Furthermore, your walls may become warped or even bow or bulge when there’s a water issue, which often leads to mold growth.


In the event that you are unable to visibly spot any signs of mold growth, you’ll likely still be able to smell the mold. Mold gives off a musty odor. It is similar to an earthy smell that you would find in a damp forest.

If you get down and smell the electrical outlets, then you will be able to more easily sniff out whether there is mold growth behind your walls. It sounds like a silly thing to do, but outlets have good access to the space behind the walls in your home.

What to Do When Finding Mold in Your Home

How to troubleshoot mold on interior walls

Make sure to call the experts at ServiceMaster to properly remediate your mold problem.

Be alert of any of the aforementioned signs. Such things are likely indicators that your home’s walls have mold growing behind them. Considering the damage that mold can have on not only your home’s building materials but also yours and others’ health, it is important that you address any mold growth immediately.

With that being said, if you find your home has mold growth, then you should seek professional mold remediation services. Professionals can thoroughly tend to the damage, contain the mold, prevent further damage and spreading, conduct necessary repairs or replacements, and even treat your home in a manner that prevents mold from returning.

Restoration professionals should be IICRC-certified and experienced to remove mold growth of all sizes. Shortly after receiving your call, their experts will be on their way to inspect the area. They will then contain the affected area to prevent the mold from spreading.

Licensed restoration companies use only the latest products and equipment in order to completely remove mold at its source. After a thorough remediation service, we will ensure that all areas have been restored to their original conditions, giving you the peace of mind that your home is safe from unsafe living conditions.

About Luke Armstrong

Expert in emergency fire and water restoration services, fire cleanup and water damage cleanup, mold removal, as well as carpet and upholstery cleaning services. Contributor to several restoration and cleaning blogs.

Some damp is caused by condensation. This can lead to a growth in mould that appears as a cloud of little black dots. For other kinds of damp, see below.

Condensation occurs when moist air comes into contact with a colder surface like a wall, window, mirror etc. The air can’t hold the moisture and tiny drops of water appear. It also occurs in places the air is still, like the corners of rooms, behind furniture or inside wardrobes.

How to troubleshoot mold on interior walls

How to reduce condensation at home

1) Produce less moisture

Simple things make a huge difference, like keeping the lids on pans when cooking, drying clothes outdoors (and especially not on radiators), venting your tumble dryer to the outside and avoiding using paraffin heaters or flue-less bottled gas heaters which produce a lot of moisture.

2) Let the moist air out and the fresh air in

Extractor fans are an effective way to get rid of moist air and steam so that less condensation forms. Some very modern homes have extractor fans which run continuously, fitted in the ceilings of bath and shower rooms. They use very little electricity. If your home doesn’t already have extractor fans then it's well worth getting them fitted in the bathroom and kitchen. Fans that run on a timer, humidistat or pull-cord typically have a rating of 8-30W. A 30W appliance would need to run continuously for nearly a day and a half to use one unit (about 15p) of electricity.

Stop moist air getting into the rest of your home. When cooking or bathing, keep the kitchen or bathroom door shut and open the window so that the steam goes outside instead.

Meanwhile, let fresh air circulate to avoid mould forming where the air is still. Make sure there is a gap between your furniture and the walls, and give wardrobes and cupboards a good airing sometimes.

3) Insulate and draught-proof your home

Warm homes suffer less from condensation, so you should make sure your house is well insulated. This means insulating your loft to the recommended depth of 270mm (about 11 inches), and your cavity walls (if your house has them). Your windows and external doors should be draught-proofed, and you should consider secondary glazing if your windows are draughty.

4) Heat your home a little more

While you don’t want to waste money heating rooms you don’t use, very cold rooms are more likely to get damp and mould. Set the thermostatic radiator valve to 1 in unused rooms so the radiator gives out a little bit of heat whenever you have the heating on. If you don’t have central heating, consider using a room heater with a timer and temperature control. Remember, unused rooms will need a good airing from time to time.

Other helpful equipment

You can catch condensation dripping from windows with condensation channels and sponge strips (available from DIY shops). If you wipe down windows and sills in the morning this will also help, but be sure to wring out the cloth rather than dry it on a radiator. In extreme circumstances you may need to invest in a dehumidifier. These can help a lot but cost anything from £40 to over £200 and larger ones can be quite costly to run.

How to get rid of mould

If you already have mould on your walls and ceilings then you need to clean it off properly. An effective two-stage method is to start by cleaning off the mould with spray containing bleach. This will help remove the staining that persistent mould can leave behind. Leave to dry overnight and then spray the affected area with an anti-fungal wash and allow that to dry. Always follow the manufacturer’s instructions and consider wearing a face mask when spraying.

You could also treat the affected area with a mould-resistant paint, available from most major hardware stores.

Condensation is not the only cause of damp

‘Penetrating damp’ is caused by moisture coming into the house through leaking or cracked pipework, a damaged roof, blocked guttering, gaps around window frames and cracked or defective rendering and brickwork. All these problems can be remedied.

‘Rising damp’ is due to a defective (or non-existent) damp course. This will leave a ‘tide mark’ about a metre above the floor. Fixing rising damp is a job for a qualified builder.

NB: Newly built homes can sometimes feel damp because the water used during its construction is still drying out.

How to troubleshoot mold on interior walls

Mold often grows out of sight in wall cavities due to water problems like flooding or leaks. Before you know it, it creates a toxic environment in your home, compromising the indoor air.

The good news is that even hidden mold leaves behind clues. You can find out if mold is growing in your walls in several ways. Here is how to spot mold that grows inside your walls.


If your home has suffered severe water damage, mold will grow in your walls if the water wasn’t removed within 24-48 hours. If water reached drywall, the best practice is to cut it one foot above the water line.

Other water problems like leaking pipes may also trap moisture inside your walls. Even in these cases where leaks are visible, moisture can get inside walls, providing mold a place to grow. Be aware of signs that drywalls are moist such as:

  • water stains
  • dark rings
  • discoloration
  • deterioration like peeling, bubbling or cracking of the paint or wallpaper

Moreover, if the walls are bowed, bulging or warped, they most likely contain moisture. Another clue is if the surface of walls feels wet or damp.

Visible Signs of Mold

First of all, if the wall is rotting, it likely has mold underneath it. In less severe cases, mold might not be that noticeable. Inspect the walls and check for mold on walls behind furniture and along baseboards too.

Mold can have different colors and textures, so be sure to recognize them. Mold can be black, green, gray, white, or brown. Mold can even appear orange, pink or purple when it grows behind vinyl wallpaper.

Another sign of visible mold is discoloration of walls, even if it has been painted over. If the water damage inside the walls persists, mold will show signs on the surface.

Musty Smell

If you don’t see signs of mold but you can smell it, it may be hidden in your walls. A musty smell is a good indicator that mold is growing in your home. The smell of mold feels earthy, like rotting leaves or decaying wood in a dense, damp forest.

If you think there’s mold in your walls, get on your hands and knees and smell the electrical outlets. This might sound silly, but it may help you sense mold if it’s growing within walls. Outlets have better access to the area behind walls. Thus, smelling them can help identify the mold problem.

To best determine if or how much mold is in your walls, consult a mold removal company like PuroClean. We use professional inspection techniques and tools to determine the existence and extent of mold. For mold removal and water damage repair services, contact your local PuroClean office.

Molds are types of fungi that may grow indoors or outdoors, usually in damp, warm, and humid environments. The most common types of household molds might be found around bathrooms, basements, drywall, ceiling tiles, carpet, wallpaper, under sinks, and around plumbing pipes.

How to troubleshoot mold on interior walls

Mold in the home can pose serious health risks, but unfortunately many don’t realize they have a mold problem because they don’t know what to look for. Here you will read a little about mold warning signs, first as it relates to your health, and secondly as it relates to the structure and history of your home.

Mold Warning Signs: Allergies and Other Health Issues

When someone has mold in their home, they usually show allergy-related symptoms. If you’re not sure whether your allergy-like symptoms are caused by mold in your home, then consider this question: do your symptoms get better once you go outdoors or leave your home? If so, then there is good chance that mold is the culprit.

Symptoms of mold allergies include:

  • Coughing
  • Sneezing
  • Sore, itchy throat
  • Congestion and runny nose
  • Sinus headaches
  • Wheezing and difficulty breathing
  • Itchy, watery eyes
  • Irritated, itchy skin

Some forms of household mold are toxic, causing serious, life-threatening illness. These highly-dangerous molds might cause symptoms such as bleeding, internal organ damage, mental impairment, cancer, and even death.

Mold Warning Signs in Your Home

Mold in the home is dangerous, as you have just read. But luckily, it’s usually easy to spot when you know what to look for. Below are some key warning signs that you might have mold in your home.

  • Mold odor. Not all molds produce a smell, but many do. If you smell a persistent musty odor, then there might be mold in your home.
  • Visible signs of mold growth. Some molds might appear white and thread-like. Others appear in clusters of small back spots. Mold might be gray-brown, black, gray-green, or white. Mold that grows behind vinyl and wallpaper might be orange, pink, or purple.
  • Signs of water damage. Any long-term moisture will inevitably lead to mold. If your home has water stains, discoloration on walls, floor, or ceilings, of if you notice bubbling, cracking, or peeling paint or wallpaper, then you’re likely dealing with mold-producing problems.
  • Water leaks. Mold growth from leaks isn’t always noticeable, especially if the leak is behind a wall or other hidden surface. If you know of a leak, then it’s important to get it repaired quickly. Areas where condensation often form can also be a haven for mold, such as windows and metal pipes.
  • Past flooding. If your home has experienced any flooding in the past, then it’s very likely that you have some form of mold growth as a result.

Mold in the home can be severely damaging to your house and your health. If you think your home might have a mold problem, seek a professional mold inspection right away. Green Home Solutions offers safe, affordable, fast, and effective mold inspection and treatment.

How to troubleshoot mold on interior walls

Dampness results from water incursion either from internal sources (e.g. leaking pipes) or external sources (e.g. rainwater). Dampness becomes a problem when various materials in buildings (e.g., rugs, walls, ceiling tiles) become wet for extended periods of time. Excessive moisture in the air (i.e., high relative humidity) that is not properly controlled with air conditioning can also lead to excessive dampness. Flooding causes dampness. Dampness is a problem in buildings because it provides the moisture that supports the growth of bacteria, fungi (i.e., mold), and insects.

In the presence of damp building materials the source of water incursion is often readily apparent (e.g., leaks in the roof or windows or a burst pipe). However, dampness problems can be less obvious when the affected materials and water source are hidden from view (e.g., wet insulation within a ceiling or wall; excessive moisture in the building foundation due to the slope of the surrounding land).


How to troubleshoot mold on interior walls

The health of those who live, attend school, or work in damp buildings has been a growing concern through the years due to a broad range of reported building-related symptoms and illnesses. Research has found that people who spend time in damp buildings are more likely to report health problems such as these:

  • Respiratory symptoms (such as in nose, throat, lungs)
  • Development or worsening of asthma
  • Hypersensitivity pneumonitis (a rare lung disease caused by an immune system response to repeated inhalation of sensitizing substances such as bacteria, fungi, organic dusts, and chemicals)
  • Respiratory infections
  • Allergic rhinitis (often called “hay fever”)
  • Bronchitis
  • Eczema

Exposures in damp buildings are complex. They vary from building to building, and in different places within a building. Moisture allows indoor mold to multiply more easily on building materials or other surfaces, and people inside buildings may be exposed to microbes and their structural components, such as spores and fungal fragments. Mold may also produce substances that can cause or worsen health problems, and these substances vary depending on the mold species and on conditions related to the indoor environment. Moisture can also attract cockroaches, rodents, and dust mites. Moisture-damaged building materials can release volatile organic compounds that can cause health problems.

Researchers have not found exactly how much exposure to dampness-related substances it takes to cause health problems. Research studies report that finding and correcting sources of dampness is a more effective way to prevent health problems than counting indoor microbes. Therefore, NIOSH developed a tool to help assess areas of dampness in buildings to help prioritize remediation of problems areas.

The National Institute for Occupational Safety and Health (NIOSH) requests assistance in preventing respiratory symptoms and disease from working in or occupying damp office buildings, schools, and other nonindustrial buildings. This Alert describes the respiratory problems that occupants may experience from exposures in damp buildings, presents summary information on outbreaks of building-related respiratory disease, and provides recommendations on how to identify, respond to, and prevent building dampness and related respiratory symptoms and disease.

Mould is a type of fungi that lives on plant and animal matter. This can include building materials like wood and gypsum plasterboard and furnishings like carpet and curtains and even books and boxes. Mould grows best in damp and poorly ventilated areas and reproduces by making spores.Airborne mould spores are commonly found in both indoor and outdoor environments. When they land on damp spots indoors, they may begin to grow and spread. There is no practical way to eliminate all mould indoors; the way to control indoor mould growth is to control the source of moisture.It is important that your home has good ventilation to minimise internal moisture and prevent mould growth.

What does mould look like

Mould is not always easy to recognise. It often looks like ‘fuzz’ or appears to be a stain, smudge or discoloration. The most common moulds are black, green or white. However, mould can be many other colours, ranging from grey to orange to brown and can also change depending on age or life-stage.

How does mould affect health

Mould associated with damp buildings can trigger nasal congestion, sneezing, cough, wheeze, respiratory infections and worsen asthma and allergic conditions.

People who are more susceptible to these symptoms and other serious health effects include those with:

  • weakened immune systems
  • allergies
  • severe asthma
  • chronic, obstructive, or allergic lung diseases.

You should seek medical advice if you are concerned about the effects of mould.

What causes mould to grow indoors

Mould only grows when there is sufficient moisture on a surface or humidity in the air. Common causes include:

  • leaky roofs and walls including and blocked gutters and downpipes
  • leaky plumbing
  • condensation from cooking, showering, clothes drying and from breathing inareas with poor air circulation eg cupboards and corners and furniture against uninsulated outside walls. Avoid conditions encouraging mould growth, by using heat, insulation and ventilation. The cheapest and easiest way of reducing moisture and humidity levels is by ventilating a room by opening a door or window. Use exhaust fans where available.

Actions you can take to reduce mould

The most important actions you can take to prevent mould in your home are those that minimise moisture.

  • Fix leaky plumbing and roofs and other building faults
  • Ensure gutters are cleared and maintained
    • Reduce condensation by using exhaust fans, or open windows in the bathroom and kitchen when showering, cooking or using the dishwasher
    • Wipe up excess water caused by condensation such as on single glazed windows and on shower glazing
    • Air the home regularly by opening windows and doors on warmer days
    • Vent clothes dryers to the outside and clean lint filters according to the manufacturer’s instructions.

    Refer to information about cleaning up mould: refer to the information on the Better Health Channel website .

    Rental properties with mould issues

    When a rental property has mould, the owner should fix any mould caused by faults in gutters or other fixtures, but the tenant should ensure that extractor fans are used when available and the home is aired regularly where possible.

    Sometimes, the cause of the mould growth may be due to a building fault that may not be easily rectified.

    If as a tenant, you have taken measures to make sure the building is properly ventilated and mould is still growing, you should raise the issue with the owner.

    Information on mould in rental properties is available on Consumer Affairs Victoria’s website

    Tenants seeking further advice on their rights can also contact the Tenants Union of Victoria on 03 9416 2577 .

    Testing for mould in your home

    Where mould is visible, it is generally not considered necessary to test for it in the home. However, not all mould is visible, as contamination may be in cavities or the ceiling. Generally, if you can see or smell mould, you need to clean up and remove the mould immediately, as mould can damage surfaces it grows on.

    If you suspect mould contamination but cannot find the source of the problem, or if you have already taken measures to prevent mould from growing and you are still having problems, you could employ an occupational hygienist or environmental health and safety professional. For a fee, these professionals can provide specialist mould testing and consultancy services.

    Where to get help

    • If you or anyone in your family feels unwell, seek medical advice from your local doctor or call NURSE-ON-CALL 24 hours a day, 7 days a week on 1300 60 60 24 for health information and advice and in an emergency, always call triple zero (000)
    • Environmental health section of your local council
    • Your insurance company 1300 55 81 81 or for National translation service, 131 450 . Call this number ask to be put through to Consumer Affairs Victoria. Tel. 03 9416 2577

    After a flood: mould and your health Community information, 2010 Department of Health, State Government of Victoria, Melbourne. More information here

    You keep everything you can see in your home clean and sanitized, but have you considered what lurks beyond your line of sight? Your walls can house dangerous black mold growth even if you clean regularly.

    Water damage can create a prime environment within walls for mold and mildew to fester.

    Learn how to spot this hidden intrusion, keep it away for the long term, and prevent it from coming back.

    What Causes Mold To Grow Inside Walls?

    There are a few common reasons mold will grow inside walls that even attentive homeowners could miss out on.

    A broken water pipe between walls allows water to pool and paves the way for mold growth. Even if you dried all the surface water, porous building materials will soak up the water and create a damp space for fungus.

    A window leak also can lead to water exposure in between walls. A small hole will lead to a persistent leak letting water flow down the inside of your wall.
    Humidity can creep into every available area of your home and take root. Inadequate ventilation will cause mildew to build up in all areas that are not sufficiently air-conditioned. People who live in hot and wet climates are most at risk of humid air causing mildew growth.

    Poor insulation and siding are some of the most common reasons mold can grow within walls. When insulation becomes wet, it stops acting as a barrier and becomes completely porous. This is a typical chain of events: the roof has a small hole that leaks on the insulation, allowing water to pool inside the skeleton of your home, making the ideal conditions for mold.

    Is Mold Inside Walls Dangerous?

    In as little as 24 hours, mold can begin to grow in damp and dark areas. The dreaded Stachybotrys chartarum, or black mold, feeds off cellulose, which both wood and drywall are made of. Oxygen, water, food, and darkness are all that’s needed to make this take root. It is both easier and faster for mold to grow than you may think.

    Black mold can cause hay fever symptoms in healthy people and lead to severe respiratory problems in people with preexisting conditions. Studies have shown black mold can cause sleep apnea, hives, rashes, and other common allergy symptoms.

    Along with the sickness this fungus can bring, the structural integrity of your walls is threatened by mildew. Since mold eats cellulose, it slowly takes apart the building blocks of your home and puts it at risk of collapse.

    Mold inside walls is very dangerous because it is so hidden. The spores hidden in crevices can be carried away by the air current of an HVAC system to infect all areas of your home.

    How to troubleshoot mold on interior walls

    How To Detect Mold Inside Walls

    Keep all of your senses keen to pinpoint the location of the fungus.

    Mold produces a unique musty smell that permeates out from its location. Sniff for a deep earthy smell like the forest floor. Get close to outlets and other holes to try and precisely locate the source.


    Water damage and mold growth often go hand in hand. Look for signs of water damage along your walls. Any discoloration from brown to yellow to black is a serious warning sign.
    Any slimy or fuzzy growths appearing is a sure-fire sign of a colony within your walls. Any color from yellow to green to purple to red to black is a bad sign.


    If you notice condensation on your walls, or they feel wet to the touch, immediately get help. Do your best to dry any surface water, and you can attempt to clean faster than mildew can grow.

    Peeling and cracking

    Wallpaper and paint should never peel or crack. Bulges and bubbles are a sign of excess moisture slowly building up over time. If you see your walls warping or twisting, you have water damage and will need to bring in an expert to properly dry and prevent a mold infestation.

    How To Remove Mold Behind Walls

    The most challenging part of cleaning behind a wall is that you will have to tear it down in order to access the affected areas. It is best to work with professionals to avoid cutting through any electrical wiring or plumbing piping.

    Should you manage to access the interior yourself, follow the same steps to remove mold from wood flooring. Create a cleaning solution of bleach and water and work in the mixture until you lift the mold completely and you cannot see any remnants.

    Lastly, you must fully dry the area. Start with a cloth to remove surface water, then run a dehumidifier for at least 24 hours so that the site will dry all the way through.

    Frequently Asked Questions

    Is Mold Inside Walls Dangerous for Babies?

    Prolonged exposure to any form of mold or damp can result in varying respiratory illnesses, including reduced lung function.

    Can Mold Inside Walls Make You Sick?

    Yes. Whenever you discover signs of mold, you should act promptly to remove them, as they aren’t just unsightly. They can be deeply harmful.

    Is Mold in Walls Covered by Homeowner’s Insurance?

    In most cases, yes, your homeowner’s insurance should cover you. Always double-check the specific details of your policy!

    Will Mold Die if it Dries Out?

    No. Drying out is not enough to kill mold entirely. However, it will significantly stunt its growth.

    Can You Live in a House with Mold Inside Walls?

    Yes, though it isn’t exactly recommended. You should look to remove any signs of mold as soon as possible to minimize damage.


    Mold inside your walls is nothing to take lightly. This project is generally above your typical DIY capabilities.

    Luckily, All Dry USA is here to save the day. With ten years of mold remediation and removal experience, we can get it out of your walls and make sure it won’t come back.

    Plus, we don’t just handle the mold; we can tackle any associated water damage as well. Trust the experts to quell your infestation and get your home back in tip-top condition.

    What Causes Mold on Walls?

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    How to troubleshoot mold on interior walls

    Mold can be a major problem for homeowners. Besides the damage it can do to the infrastructure of your home, mold is a serious health risk. Even if you’re healthy, mold can lead to respiratory issues, skin problems, and headaches.

    Mold doesn’t grow out of nowhere. When you start seeing signs of mold on your walls, it’s time to reassess the potential causes.

    Most people understand that mold thrives where excessive moisture is present, but fewer realize how many opportunities there are for moisture to accumulate in a house. There are three common causes of the moisture that invites mold to grow, all of which are preventable with a little forethought.

    Reason #1: Humidity

    Humidity is the primary cause of mold on walls. If you live in a humid area, an easy solution is to purchase a dehumidifier, and move it to different rooms on a regular basis to ensure that all areas are adequately covered.

    For larger spaces, it may be worth purchasing multiple dehumidifiers. Even homeowners in dry areas should watch out for appliances that use significant amounts of hot water, since this can make the surrounding air more humid even in an arid region. Clean behind your laundry machines regularly, open the windows when you shower in the bathroom or wash dishes in the kitchen—and make sure your home is well-ventilated at all times.

    How to troubleshoot mold on interior walls

    Reason #2: Condensation

    Condensation occurs naturally on the perimeter walls of your home, which are often cooler than the air inside your house. As a result, the water in the air can experience a temperature drop when it touches these walls, and undergo a change of state to become liquid. If this liquid is left alone too long it will become an ideal breeding ground for mold.

    Inspect any outside walls of your house regularly to prevent moisture buildup. It may also be worth installing double-stud walls, which all but eliminate the risk of condensation.

    Reason #3: Water Leaks

    The third most common cause of mold on residential walls is also one of the simplest: leaks. If your pipes drip, water is likely making its way into the framework of your house every time you turn on the tap.

    As this moisture builds up over time, it becomes a potent hotbed for all kinds of bacteria, and mold becomes inevitable. Check your pipes frequently, and make sure that you take steps to keep them from leaking when the temperature in your area changes. Leaks often occur when winter arrives and the sudden cold warps the metal in your pipes, causing it to crack. Invest in insulation for your pipes, drain outdoor faucets before the water in them has a chance to freeze, and consider letting your indoor taps drip steadily overnight to keep the water in them moving.

    Mold is a homeowner’s worst nightmare, but it doesn’t have to be yours. Use the tips listed in this guide to mold-proof your home, and you’ll be able to enjoy living in comfort and mold-free for as long as you want. The best part? Reducing risks of mold will ultimately increase the value of your home, and make it safer for your whole family.

    How to troubleshoot mold on interior walls

    You’ve probably heard about the dangers of black mold, an alleged silent killer that hides in water damage and ceiling tiles. But what is black mold? And is it dangerous?

    Black mold, or Stachybotrys chartarum, surfaces as blackish-green spots or blemishes. It lives on moist, cellulose-rich surfaces like fiberboard, drywall, and gypsum board. Black mold is most attracted to moisture, which is why it lives in previously-flooded homes, leaky pipe areas, or anywhere with water damage.

    How to find and remove black mold

    How to troubleshoot mold on interior walls

    Is black mold dangerous?

    The short answer is—not really. But that doesn’t mean you should keep black mold as a pet.

    Everyone has different levels of tolerance to allergens like mold spores, but that’s all black mold is—an allergen. 1 Those with asthma, respiratory allergies, or immune suppression will feel the effects of black mold’s mycotoxins more than most folks.

    As one source put it, “Previous reports of ‘toxic mold syndrome’ or ‘toxic black mold’ have been shown to be no more than media hype and mass hysteria.” 2

    But whether you feel black mold symptoms or not, it’s best to get rid of black mold as soon as you find it.

    What are the symptoms of black mold exposure?

    If you find black mold on your property, there’s no need to panic. But black mold presents more health risks to sensitive groups like those with respiratory conditions or immune conditions.

    According to the Centers for Disease Control (CDC), black mold spores can generate cold- or flu-like symptoms such as:

    • Stuffy nose
    • Wheezing
    • Skin and eye irritation

    Longer exposure can cause more serious symptoms like:

    • Fever
    • Shortness of breath
    • Nausea

    So while black mold probably won’t kill you, it can make you feel sick and should be removed as soon as possible.

    How does black mold get inside a house?

    Mold spores find their way inside by hitchhiking on clothes, pet fur, and air currents into your home. But spores can’t get comfortable without plenty of water. This is why you’ll usually find black mold around water-damaged areas impacted by plumbing issues like floods or leaky pipes.

    Materials like drywall, carpet, or gypsum board can soak up water, creating a perfect home for a black mold colony. If you find water damage at home, it’s crucial to remove all the affected materials to prevent mold from growing.

    A water leak sensor can alert you to leaks in hard-to-reach places where the water damage would otherwise go unnoticed.

    Black mold removal and cleaning

    Mold remediation in stores, offices, or schools is best left to the pros. This also applies to household mold exceeding 10 square feet.

    The contractors you choose should have insurance and licenses from organizations like the Institute of Inspection Cleaning and Restoration Certification (IICRC).

    Homeowners can handle cleaning about 10 square feet (roughly 3 feet by 3 feet) of black mold on their own. 3 If the patch is small enough, a combination of bleach, water, scrubbing, and ventilation should do the trick.

    Before treating mold on your own, prioritize ventilation and protective gear.

    Removing black mold is a tough and dirty job. If you or anyone in your family is sensitive to mold allergies, has respiratory or immune issues, trust the professionals.

    Find a contractor in your area to get started.

    Clear the air

    Start the cleaning process by opening doors and windows to create a cross breeze. Dehumidifiers can also dry up the air and strip precious moisture away from mold growth.

    Protect yourself

    Even if you aren’t sensitive to mold, it’s nasty stuff. Be sure to wear protective eyewear, non-porous gloves, and a mask or respirator to protect yourself from getting sick.

    Create a bleach mixture

    If the black mold growth in your home is small enough for you to treat alone, a simple mixture of bleach and water can help. Add one cup of bleach to one gallon of water and apply it to the moldy spots. You can also find commercial black mold removal products.

    Soak a paper towel in the cleaner and press it over the mold growth to dampen the area. Then start scrubbing. Avoid spraying moldy areas, since the droplets will collide with the mold spores and launch them throughout the room, making them easier to breathe in and harder to eradicate.

    Be sure to dry the area thoroughly when you’re done.

    Do NOT mix bleach with ammonia . This combination can create toxic fumes that are far more dangerous than any mold you’re trying to clean.

    Removing mold from walls is a must to keep your home hygienic. There are different ways to tackle small areas of mold on walls with vinegar, steam, bleach and more but you should know when to call in an expert.

    How to troubleshoot mold on interior walls

    If you need to remove mold from walls around the home then you should act fast. The less mold growth you’ve got to deal with, the more successful you’ll be. And, you’ll want to tend to it quickly to know whether there’s a bigger issue at hand.

    If you’ve noticed small black dots – or patches – forming on a wall, reach for your rubber gloves now. Getting rid of mold around the home isn’t the best chore but if you ignore mold, the problem will get worse.

    Plus, breathing in mold spores is bad for you and it can make problems like allergies and asthma worse; the mold itself can damage plaster and wall coverings, too.

    John Otero, Regional Director of PuroClean, “The Paramedics of Property Damage,” who are experts in mold remediation services says, ‘Although it is safer to hire a certified mold remediation specialist, there is a chance that you can remove the mold yourself if there is a small amount of mold or where the mold is limited to the surface, as long as the affected area is smaller than 10 square feet.’

    ‘You must wear protective clothing to reduce exposure and a mask to protect your airways. The affected area must be isolated so that it does not spread to other rooms and areas of the home.’

    How to remove mold from walls

    ‘There are many ways of dealing with mold on walls, but ultimately it will depend of whether the mold is ON the wall surface, or if it’s IN the surface. Mold will grow on a painted surface if there is a constant supply of moisture in the air, as well as a food source for the mold spores to take advantage of.’ Says Andrew pace, Founder of The Green Design Center.

    ‘Take a bathroom for instance… steam from a hot shower will carry soap particles and dead skin cells along with it and eventually these attach to a wall. Any mold pores in the air will eventually land on that surface and proliferate. So, reducing the moisture by eliminating the shower steam will be the most effective way to reduce the possibility of mold growth.’ Adds Pace.

    David Mason, the owner of The Knobs Company, a home solutions company comments, ‘The best way to get rid of mold on walls is to use bleach and detergent. If you want to be more natural, you can use a mixture of water and vinegar. If the mold is on the ceiling, you should remove it using a mixture of bleach and detergent. As long as you have a moldy wall, it’s going to continue to produce spores. If the mold is due to humidity, you need to fix the problem.’

    1. How to remove mold from painted walls – with or without bleach

    Some swear by bleach for many cleaning jobs around the home including mold removal but where possible we try to keep things as natural as possible. Otero suggests using a regular household detergent instead:

    ‘Dry the affected surface and scrub the walls using a mixture of household detergent and water (don’t use bleach), and then dry the surface as thoroughly as possible; try not to leave any moisture behind.’

    Pace recommends bleach for a quicker option but says you can still use detergent if you prefer, ‘It’s best to take down the paint, although if you have an acrylic wall, you can place a solution of bleach and water over it to kill the mold. You can also use a mixture of detergent with water to remove mold from painted walls, although it might take more time.’

    Masson comments, ”The most natural way to remove mold from walls is with a mixture of water and detergent, although if your major goal is to get rid of the mold, bleach will be a more effective weapon because it kills mold. If you have to choose between naturalness and effectiveness, go with the latter.’

    If you are using bleach to remove the mold from the walls, wear gloves and a mask if possible. Then start by making a solution of one part bleach to three parts water, or use a household bleach spray. Apply to the mold, scrub with a stiff brush, rinse and dry. Repeat if necessary.

    If you’re tackling mold on bathroom walls, you can use bleach diluted one part with two parts water in a spray bottle; apply, allow to dry, apply again and scrub with your stiff brush. Rinse and repeat.

    Kyle Richards, Co-founder of Best Overland Park Painters shares his method for cleaning mold off painted walls: ‘Removing mold from walls can be done naturally by any DIY enthusiast. All you really need is a spray bottle and any of these three substances: hydrogen peroxide, vinegar, or baking soda. All of these are effective in killing the mold sticking to your walls. In the case of baking soda, it’s even effective in preventing the mold from coming back.’

    ‘For painted walls, you have to be as gentle as you can to avoid scraping off the paint. This is why out of the three, I recommend hydrogen peroxide or vinegar the most, at least for physically removing the mold.’

    2. How to remove mold from walls with vinegar

    Vinegar – a mild white one is a good choice – can be sprayed on undiluted, left for an hour, then rinsed with hot water and dried with a microfibre cloth. It’s ideal even for getting rid of mold on drywall.

    Otero adds that it is one of the most natural methods to combat mold growth on walls, ‘The most natural way to remove mold is with vinegar. Add white vinegar to a spray bottle (no water) and spray the vinegar on the surface mold, letting it sit for 30-minutes. Wipe the area clean with water. The vinegar smell will clear after 2-3 hours, but you can open a window to help aerate the space. This solution will work on both nonporous and porous materials, like drywall.’

    Pace comments that if mold has begun to attack the drywall, then a more natural solution may not be sufficient. If mold is on the wall’s surface, you can up the ante with borax, ‘If mold does start to show on the surface, using a mixture of warm water, vinegar and borax in a spray bottle will remove the mold. If the situation is left to feature too long, mold can actually eat through into the surface of the paint and attack the drywall. At this point, the “natural” cleaning method won’t work.’ Should you try borax, be sure to wear appropriate safety gear also as it can be an irritant on skin.

    3. How to remove mold from walls using steam

    Steam can be a powerful cleaner and if often used to tackle dirty carpets and upholstery. Kaärcher boasts some of the best steam cleaners on the market and UK Retail Assistant Product Manager, James Mokler notes how ‘Steam can be used to remove mould from interior walls, however this is all very dependent on the surface itself – some painted surfaces can be more sensitive than others. We’d recommend testing a small area of the wall on a low steam pressure utilising a microfiber cloth first to understand the sensitivity of the wall. After this more pressure and agitation can be used using our various accessories. Mould can easily be removed from tile grouting within the shower utilising the small bristle brush accessory.’

    4. Using a mold remover spray to treat walls

    You can of course use a mold remover spray – both on walls and other surfaces around the home (always check the application areas before buying).