Signs Of Mold In Walls – What Does Mold Smell Like In Walls

You’ve found some mold on your walls and are worried there might be even more mold Inside your walls?

You notice a mustly smell and based on that, want to determine for sure what it is?

This guide will help you do just that and cover all aspects of mold inside walls.

Not Only mold inside your walls can damage the structural integrity of your home & damage the foundation of your house – It can also be extremely harmful to your health.

Therefore, it’s extremely important to get the mold-infested area removed and cleaned right away.

Besides causing damage to your home, mold inside walls can have detrimental effects on one’s health and cause:

  • Allergic reactions
  • Trouble breathing
  • Itchy skin
  • Eye irritation
  • Cold/cough sustained for long period of time

What Does Mold Smell Like in Walls?

The most common smell associated with mold inside walls is a musty one.

Anything that smells wet, like old water-infested wood is a sign that you likely have mold growing in the walls.

If the smell gets stronger in certain areas of your wall or you are seeing peeling wallpaper and wall discoloration – There might be Mold Infestation inside your walls!

Signs Of Mold Inside Walls

If you are uncertain whether mold is in your walls, a few clues can help you determine this.


A strange smell, usually musty, is one common sign. This is especially the case if the area is moisture-prone or took on water from a flood or leak.

The smell will be confined to a specific area, and if you notice this, you want to have it checked out. Assuming it’s mold, remove it immediately.

Wall Colors

Black spots on the walls, a yellow-green color or brown can be indications that mold is present.

The substance often penetrates the surface, so look for water stains.

Additionally, general discoloration, cracks, peels or bubbles on the surface of the wall you can see can be signs that there is also mold behind the walls.

Excess Moisture

Whether it’s from rain, toilet or sink overflow, leaking pipe, flood or even extra condensation-water will cause mold.

If your wall looks wet or recently took on water, you can bet that mold likely will develop if it isn’t dried out properly.

That’s why it’s important to remove the water right away, inspect for mold and do what you can to mitigate the situation.

If it’s not something you want to take on, you can always call a professional company who has the experience and knowledge in this type of work.

Most Common Causes Of Mold Inside Walls

Mold can develop in walls after a flood, leak, or any type of water damage. Other causes include high humidity, lack of insulation and faulty AC condensation.

If left untreated, it can eat away at the wood, causing it to rot and doing damage to the structure of your house.

This can lead to significant and costly repairs.

While most of the time excess moisture and poor ventilation are what lead to mold, let’s take a detailed look at how water can get inside the walls and cause mold.

Floods & Plumbing leaks

Any infiltration of water is a common cause of mold inside walls.

This can occur naturally from weather such as heavy rains or because of an issue within the home.

Examples include:

  • Toilet leak/overflow
  • Tub overflow
  • Sink overflow
  • Leak in pipes or from the roof
  • Water heater malfunction
  • Sewer line backup

If this happens, remove the water right away and dry the area as fast as possible.

The less water, the better, and the faster it gets cleaned up the less likely it is to spread and cause more damage.

Insulation Problems

Cracks, improperly sealed windows and thin walls are other common causes of mold behind walls.

Have your insulation checked and consider adding if needed.

This won’t only help keep moisture and water from getting into your walls, it also will prevent cold air from coming in during the winter and hot air from doing the same in the summer.

This will lead to more energy efficiency and a reduction in utility costs.

If you notice any cracks on the siding or walls, have them filled in and have your windows checked to make sure air isn’t coming through.

If it is, you can have them sealed or replaced.

High Humidity

High humidity is a leading cause of mold.

You can run a dehumidifier, turn on vents in the bathroom when showering, and make sure you are taking the necessary steps to reduce the humidity any place where it’s high.

The more air circulating from vents or open windows, the less likely you are to experience humidity that can seep into the walls and cause mold.


Any Home can suffer from condensation issues.

The moisture created can get into the walls and potentially cause mold.

Check to see if there’s a lot of water or moisture around the outside of your home.

Watch your AC unit too and look for excess water that might get into the nearby side of the house.

Suspecting Mold Inside Walls?

Call 844-488-0570 for a Risk Free estimate from a Licensed Mold Remediation Specialist in your area.

We Can Help Remove the Mold from Inside your walls & Prevent it from returning.

How Is Mold In Walls Detected & How To Test For Mold Inside Walls

If you suspect mold inside walls, you have multiple options for checking.

Some are more invasive and require more time and work than others.

The most surefire way is to cut into the wall so you can see what’s behind it.

If you don’t have the knowledge to do this or are not sure how to repair the wall afterward, contact a professional.

You can also detect and test mold through these methods:

  • Smell the electrical outlets to see if that mustiness is there
  • Purchase a moisture meter to check moisture levels in your wall
  • Use a temperature-measuring device to detect changes in temperature, this can be a good indicator that there is a problem.
  • Look for physical differences in the wall.

How Do I Remove Mold From Inside My Walls?

Unfortunately, Removing mold from inside walls can be extremely difficult as it will require removing & replacing your drywall.

After the Drywall is removed, if it’s clearly mold-infested- it will need to be binned as mold can thrive and grow in drywall.

Often you will even find the mold growing inside your wall insulation, If this is the case – that will need to be replaced as well!

After the infested material has been removed you will need to clean and Kill the mold on your Studs inside the walls.

The most effective mold Killer to go for is the RMR-86 Mold Killer, alternatively, ConCrobium Mold cleaner can be used as well.

There are other DIY ways this can be done as well which will provide good results,such as:

  • Bleach-water mixture (1-8 ratio), put in spray bottle, spray area where mold is, let it sit for 20 minutes and wipe with brush, sponge or rag
  • Spray vinegar on affected area, let it sit for 30-60 minutes, wipe clean. You can also use a mixture of hydrogen peroxide and vinegar
  • Mix borax with water and spray

No matter which option you choose, wear protective clothing, gloves and goggles.

These are strong substances and can cause health hazards when released.

Aim on the side of being overly cautious to protect yourself when removing mold from walls and take safety precautions.

If there is mold inside your walls , and you need to remove your drywall to get rid of the mold – This is often best left for a professional.

Preventing Mold Forming In walls

The best way to prevent mold from forming is to limit moisture and water from getting on your walls.

There are several ways to do this including more insulation, sealing cracks, keeping areas such as bathrooms and basements dry as well as running dehumidifiers.

You can keep shower doors open after using so the water escapes and wipe the floor too.

Good Ventilation inside your home is extremely important as well to prevent any mold from forming in your walls.

Open windows, use bathroom fans and make sure your home has good ventilation where it’s needed.

Keep humidity to a minimum, especially in areas more prone to this.

The recommended moisture reading level is 50% or less.

Look for leaks in ceilings and on the roof. Should you have any, repair right away.

This is another significant measure to prevent mold from getting into walls.

When To Call A Professional

You might want to make this your first option if you suspect there is mold growing inside your walls.

They have the knowledge to assess the damage, recommend the best way to remove mold and get the job done. 

If the mold is widespread, It would be extremely tough for an individual to remove it himself when found in large areas or several different places in the same house.

Professionals likely will use strong, industrial-grade chemicals to remove mold inside your walls and prevent it from returning.

Not only it will save you time and effort but also risk – given how hazardous certain types of mold can be.

Mold can be very dangerous, can cause many problems and you should take the necessary actions to prevent it from developing and removing it when you see it.

We have Mold Remediation Specialists that can help Remove Mold from Inside your walls & Prevent it from returning.

For Disasters of all Sizes,available in 95% of the USA

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