How To Detect Mold Behind Walls? Complete Step-by-Step Guide

Helen Skeates
Helen Skeates
23 min read

When your home has been damaged by water, you’re more than likely going to see mold growth. If the water damage is severe, mold can begin to form on your property within 24 hours of water soaking through the drywall. If you have leaking pipes in your home, they can cause water damage and, more likely, mold growth.

Mold Testing: How to Test for Mold for the Home

What does mold look like

Mold may be found just about anywhere. Fungus that grows from airborne spores is known as an airborne fungal spore. It can thrive in temperatures ranging from 40 to 100 degrees Fahrenheit, just about everywhere spores land. About every moist spot in your house is likely to be included in this category.

The most obvious mold, known as mildew, begins as little, black dots but typically expands into larger colonies. You can quickly recognize this sort of mold. It’s one of the most straightforward methods of determining whether or not you have mold. Grout lines in your shower, moist walls, and painted siding in damp and shaded areas are all places where you’ll find it. It’s the black gunk you see. It can be tough to tell the difference between a mildewed and an unclean surface.

Dab a few drops of household bleach on the blackened area to check for mold and mildew and how to identify whether your house has mold. If after one to two minutes, the mildew begins to lighten, you got it. If the region is still black, it is most likely filled with dirt.

How to Know if Mold Is in Your Walls | Restoration Blog | RestorationMaster

Is it Mold or Dirt?

The majority of mold is easily recognizable, while minor or largely hidden growths might simply make a surface appear unkempt. You may quickly test for mold by dabbing a swab on the wall with diluted bleach (1 part bleach to 16 parts water). Assume mold if the spot quickly fades (or continually reappearing after cleaning) Although mold test kits are readily available, they cannot help pinpoint the cause or recommend a course of action for dealing with the problem.

Probe the Area with a Screwdriver

Mildew is a type of mold that does not pose a threat to the structural integrity of your home. However, rot can be caused by various types of mold. Probe the questionable area with a screwdriver or other sharp tool to test for mold if you want to learn how to locate mould in your house. The fungi have taken hold and decay has commenced if the wood is soft or crumbles.

Check for Plumbing Leaks

It’s likely that a nearby leak is feeding the mold if you detect it near water pipes and other water- or waste-related plumbing equipment. Turn on the water and keep an eye on the pipes and the surrounding area to see if there is any water damage or mold growth. The real leak may be some distance away from the mold since water can move in any direction—down, sideways, or even up—when it wicks into absorbent material like drywall. Fix the leak once you’ve located it. When inspecting cabinets and other hard-to-reach areas, this lightweight work light is ideal. Learn how to remove black spots from the bathroom by reading this. Is it ok to use bleach in the bathroom to clean it? Discover the solution right here.

Look for Outside Leaks

A leak in the wall or roof can be used to check for mold on an exterior wall or ceiling. Using a reference point like a door, determine the opposite side of the wall or ceiling from where you took your measurements from the moldy area. Inspect vents, roof flashing, decks, window wells, and any wood that is deteriorating for signs of rot. Look for sloping ground and downspouts that empty adjacent to the wall if you find any of these issues. Groundwater seeps through the foundation or slab if the ground is too wet, causing a constant wetness. When repairing a leak, be sure to use correct flashing.

Inspect the Ductwork

Even though the roof appears to be leak-free, mold might form on the ceiling around ducts or registers if they are poorly insulated. On the ducts that transport cold air through the attic or crawl space, wet, warm air condenses to generate water. The condensation is a symptom that the duct is not properly insulated or has a vapor barrier that is leaking. Mold spores (which are ubiquitous) begin to grow as the water seeps into the insulation and drywall. In the winter, the polar opposite occurs. At the open junctions between duct sections, moisture accumulates whenever warm air escapes. Inspect the ductwork in your home for signs of mold. Find out how to properly insulate the rim joists in your basement.

Testing the Mold

Routine mold sampling is not recommended by the Centers for Disease Control, and identifying the type of mold is not important because it all has to be eliminated. Testing can be expensive, and there are no clear guidelines for determining what constitutes an adequate amount of testing.

Know the Differences Between Mildew and Mold

Mold and mildew come in a plethora of forms, but they all share two characteristics: In the first place, their primary function on Earth is to break down the organic matter that surrounds them. Secondly, they all require water to activate their digestive enzymes. Mold and mildew are distinct, but for our purposes, we can refer to the entire gang as a single mold. Molds do not belong in the plant or animal kingdoms. Enzymes and spores are found in these microscopic creatures, which are responsible for decomposition and digestion (in charge of reproduction).

Among the fungi are mushrooms, yeast, and other unappetizing features, such as mold. Yet these decay microbes aren’t at all unpleasant, as it turns out. It would be impossible to decompose fallen trees, slain animals, and fallen plants without them. The dead stuff would keep piling up on our land. Without penicillin, we wouldn’t have cheese or other common foods and medications. When mold begins eating away at things you don’t want it to, problems develop, including changes to your home’s appearance, odor, and structural stability.

How to Remove Mold

Take particular measures if you have to remove more than a few square feet of mold concentrations or if you detect substantial water damage when performing mold removal. Avoid infecting your home, but also protect yourself from inhaling high concentrations of spores and VOCs by sealing off the area where the mold is growing.

  • Do your cleanup work in old clothes and shoes that may be washed or thrown away.
  • In addition to goggles and gloves, make sure you’re using special N-95 or P-100 respirators.
  • Make sure the room is well-ventilated by placing an old box fan or an inexpensive new one in a window while you are working. Because the spores are nearly impossible to remove, toss it once you’re done cleaning. Keep spores out of your home by taping plywood or cardboard to the window frames.
  • Dispose of moldy carpet by wrapping and taping it in 6-mil plastic and double-bagging moldy debris in garbage bags.
  • Spray moldy spots with a garden sprayer as you work to keep airborne spores from spreading.
  • Cover ducts and doorways with duct covers to keep spores out of your home.
  • When vacuuming, use a wet/dry vacuum that is kept outside.

Use an Antimicrobial Spray

Spray an antibacterial agent on the area once it has dried to keep mold from returning. When dealing with musty scents in basements or other big spaces, fogging the entire space may be more effective. To combat mold, you can use Concrobium Mold Control, an antibacterial treatment available at home centers and online.

Use Soap and Water to Remove Mold

Soap and water are the finest tools for removing mold because they include surfactants, which aid in the mold’s removal. Some people claim that bleach and water can be used to eliminate mold, but bleach does not have the same qualities as soap and water in removing mold.

Problems Caused by Mold

Concerningly, mold will continue to devour harmed building components as it develops and spreads. Mold can also wreak havoc on your home’s air quality and represent a health risk to any and all of its occupants. Some of the health difficulties caused by mold include eye, nose, and throat discomfort, as well as coughing and a runny nose.

Mold can wreak a lot of damage if you don’t know how to tell whether it’s in your home. In other cases, mold might be difficult to detect because it can be disguised by other materials. Mold development behind your home’s walls is one example of this.

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

Discoloration and Stains

Water stains can be an indication of mold because it is often the result of water damage. Consequently, if there are visible water stains on your walls, it is highly likely that mold is forming behind them. It’s important to keep an eye out for yellow or brown water stains on your wall. It’s evident if the patches are wet that there’s a problem with moisture.

Discoloration on the walls of your home might also be a sign of mold growth, even if you’ve just repainted them. In the event of internal injury, discoloration can occur.. Mold will still be visible on the wall’s surface, thus this is why it is necessary to remove it.

Mold can appear in a wide range of colors, including black, white, brown, gray, and even green in some cases. Mold will appear pink, orange, or purple if your wall is covered in vinyl wallpaper.

Surface Changes and Deterioration

If you have mold growing behind your walls, you may notice a dramatic change in their look. Your walls may degrade in addition to being discolored and stained. Moisture and mold can cause paint or wallpaper to crack, peel, or bubble. Additionally, if you have a water problem, your walls may get deformed or even bow or bulge, which commonly leads to the formation of mold.

Mold Removal: How To Detect and Remove Mold From Behind Walls


Regardless of whether or not you can see any symptoms of mold growth, you can almost certainly smell it. Mold emits a stale, stale stench. You may compare it to the earthy odor of a damp forest.

Getting down on your hands and knees and sniffing around the electrical outlets will help you detect mold in your walls. In spite of the fact that it may appear to be a ridiculous idea, outlets have easy access to the space behind your walls.

What to Do When Finding Mold in Your Home

Observe for any of the above indicators. These are possible signs that mold is spreading behind your home’s walls. With regard to both your home’s structural materials and the health of both you and your family, it is critical to handle any mold growth as soon as possible.

That being said, if you discover mold in your house, you should contact a professional mold remediation company to handle the situation. In addition to repairing or replacing damaged items and preventing further damage or spread, they can also treat your house in a way that prevents mold from returning in the future.

Mold removal should be handled by IICRC-certified and experienced mold remediation professionals. Their professionals will arrive quickly after receiving your call to do an inspection. They will then enclose the mold-infested area so that it doesn’t spread to other parts of the building.

All goods and equipment used by licensed restoration companies are the most recent and cutting-edge. We’ll make sure your house is safe to live in after a complete remediation service, and we’ll make sure it’s restored to its previous condition.

5 Signs You Have Mold Inside Walls And How To Deal With It

1. Water In The Foundation

Your home’s foundation should be checked for water buildup. Your home’s foundation may be compromised if there is a lot of water. By sloping your yard outwards from your foundation, you can avoid rainfall from accumulating at your home’s base. In the same vein, wet basements are also a factor. Basements are usually poorly ventilated. Compared to other rooms in the house, basements may have higher humidity or moisture levels. Also, basements tend to be colder than the rest of the house, which means that more condensation forms, resulting in basement humidity.

2. Flooding

Mold can also grow as a result of water damage. If your home has been flooded, mold cleanup issues are inevitable. Your house will be soaked, and drying it out may take some time. Drying out your house could take weeks. In other words, there’s a good chance that mold will grow. Remember that mold can grow in as little as 24 hours.

3. A Leaking Roof

Mold growth can be undetected for a long time if a roof leak, such as a pipe leak, goes undetected. Check for leaks in your attic on a regular basis to keep it in great shape. The ceiling directly before the attic is a good place to look for water spots, so be extra careful there.

4. Pipes Leaking

The most typical source of mold formation is water spilling from a pipe. There is nothing worse than water leaking through a ceiling or wall that you can’t see. Mold can grow on unseen leaks, and it may have already spread.

5. Poor Humidity

Mold thrives in a home that isn’t properly aired. Moist, stagnant air is an ideal breeding ground for mold when proper ventilation is missing. Heat from steam and water vapor condensing in the air produce humidity. For it to be circulated outside, it needs to have a stable moisture content.

Remember that mold thrives in particular situations. Mold spores, a source of food such as cotton, drywall, or wood, and a source of moisture are all necessary conditions for the growth of mold.

Signs of Mold Growth

In most cases, if you notice the presence of mold in a food item, it simply indicates you need to throw it away. However, a property with a lot of mold can be hazardous. Because some mold species create mycotoxin, a compound that causes headaches, respiratory difficulties, and even neurological damage, this is the explanation. Sneezing, a runny nose, and an unpleasant odor are all possible side effects. There are other symptoms that your home contains mold that are less obvious. Mold can be the cause of a musty odor emanating from your heating or cooling system. Mold thrives in particular on air conditioning equipment that are installed on their own. When not in use, they’re dark, moist, and frequently exposed to higher temperatures. Mold is more likely to grow in a hot closet or basement during the winter if an air conditioner is installed.

How Do I Detect Black Mold Inside My Walls In The First Place?

Mold can also cause peeling wallpaper. Scuffiness and discolouration are inevitable, but odd surface or peeling anomalies like bubbling or crackling can be a clue that the walls in your room are wet. Remember that wetness is always a reliable indicator of mold. Keep an eye out for any places that appear to be moist and twisted.

Regular inspections by a professional can help prevent the growth of mold in your cooling or heating systems. The dark grout between bathroom tiles is another sign of mold in the home. There may be flooding in the neighboring room or a leak in the bathroom plumbing that produces a more dangerous fungus type that only professionals can remove, even if this type is most likely innocuous. If you send a sample to be tested, you’ll find out if your shower is safe to use.

Mold may also be to blame if you have pre-existing breathing issues that tend to worsen when you spend a lot of time at home. People who do not suffer from breathing problems are unlikely to be affected by many types of mold found in the home. In people who have asthma, however, it could worsen their symptoms. In cases when your breathing is getting worse and there is no obvious cause, consider a mold inspection and an appointment with a medical professional.

Mold can take on a wide variety of hues, textures, and forms. As a result, they can look like dripping green slime or a harmless grey fluff. A double leak in your pipes may be the cause of peeling paint on the walls or an unusually high level of dampness in the area.

Sneezing and a runny nose are just some of the symptoms that might accompany a mold reaction. A persistent cold could be an indication of a mold problem that’s hiding in plain sight. Notice if your cold gets worse when you do laundry in the basement or spend time in a certain room. There’s a good chance this is the room with the most concealed mold.

If you’re constantly sneezing, you may have a mold problem. Mold exposure can cause seasonal allergies that you didn’t know about. Even if you go to work every day and notice a decrease in your symptoms while you’re at work, you may have a mold problem at home.

If you use a humidifier in your bathroom, you may be encouraging the formation of mold. Using humidifiers on a low setting during the dry summer or winter months should not cause too much of an issue. To avoid the growth of mold, it is important to keep an eye on the humidity levels in your home if you use a humidifier on a daily basis.

As it turns out, modern dwellings are equally as attractive to mold as their older counterparts. Mold may thrive in modern dwellings because of their lack of ventilation. Houses that have recently been constructed do not have the loose construction of older, drafty stone structures, therefore moisture and wet spots tend to gather rather than be vented out as they arise. Modern appliances, such as dryers, dishwashers, and microwaves, also produce heat and moisture that fungi need to thrive.

Mold is a foregone conclusion after any type of flooding. When a basement floods heavily, most people assume that mold would grow as a result. There are many things that might lead to mold growth, such as leaking pipes and overflowing bathtubs.

Toxic mold has diverse effects on different people. A common symptom of a suspected mold reaction is exhaustion. Mold may be to blame if you’re constantly dozing instead of waking up energised.

Even if you’ve done an intensive general cleaning, mold may be the cause of a musty odor in your home. If the musty stench is more concentrated in one room or area of the house, mold may be to blame rather than a lack of cleaning. If the musty odor persists after you’ve removed the trash, steamed the drapes, and cleaned the carpet, it’s likely mold.

Almost all are able to develop in damp conditions, such as the basement, as well as infest garments. This is especially true if you’re wearing wet clothing. Mold can grow on your clothes and hurt your skin if you dry them on an outside rack or leave a wet towel on the floor. To avoid this, try to dry your wet clothes as soon as possible. Keeping your shower area clean and free of dripping towels is essential.

5 Signs You Have Mold Inside Walls And How To Deal With It

Can I Just Get Into The Wall and Use Bleach To Clean It?

There is a strong temptation to get into the wall and do the bleaching all by yourself. If you’ve never done this before, it’s best to call in a professional who is trained in mold remediation. That’s particularly true if you’ve never gotten in there and don’t know how far the mold has spread. Your health and sanity will be saved if you hire a professional to remove mold from your home. All the safety gear, detecting tools, and methodologies needed by a professional mold remediation crew will be available to you.

How Do I Remove Mold From The Inside of My Walls?

The extent of the damage caused by mold in your walls cannot be determined by you alone. If you have any of the following illnesses, removing mold from within your own walls could be risky.

  • allergies
  • asthma
  • a lack of oxygen
  • a rash on the skin
  • itchiness
  • fatigue

The removal of mold should be left to the professionals unless you are a certified mold expert. Doing this on your own could make your symptoms worse and exacerbate any existing issues. You may end up spending more money in the long run if you try to fix things on your own because of your mold-related problems.

Why Is Mold Growing on My Base Molding and Lower Part Of My Walls Only?

Having mold on the base molding of your lower walls, but not on the top parts of the walls, suggests that moisture is leaking out of the walls, but only from the baseboards. If you live in a basement, this could indicate a burst pipe or water damage to the foundation of your home. Keep in mind that mold is a result of moisture, therefore if you have moisture, you have mold. If you suspect that your foundation has been damaged by water, contact a water damage restoration company.

What should I do if I constantly notifying my landlord that I believe there is mold in my walls?

What Is The Best Way To Prevent Mold Inside Walls?

Keeping your walls dry is the most effective technique to avoid mold growth. Call a professional every few months to do a professional mold test in your walls. That way, you may be certain that there is no mold in your walls.

I have mold inside my closet walls, and there is no leak?

If your closet walls are covered in mold and there appears to be no leak, your humidifier may be to blame. After a few days without using your humidifier, check to see if the mold has stopped developing. If this doesn’t work, seek the assistance of a professional to determine the root of the problem.

I Found This Yellowish Fungus Growing From Inside The Walls?

No matter what color the fungus is, if you find it in your walls, you should contact a mold removal specialist right away. Toxins from mold and fungus might be harmful to your health if you try to fix the situation.

Is Mold Inside Walls Dangerous?

For each mold species, the toxicity threshold is different. Mold in your walls is a sign of dampness, which can lead to decay in addition to mold. The level of toxicity varies depending on the type of mold. Call a professional to ensure that you don’t mistakenly come into contact with hazardous mold. If you suspect that your walls are infested with mold, contact a mold treatment service immediately.


Even if you’ve done a thorough cleaning of your home, mold may still be causing a musty odor. Mold may be generating a musty stench in a specific region of the house or a corner of a room, rather than a lack of cleaning.

Mold is most likely to blame if the musty smell persists even after you’ve removed the rubbish, steamed the drapes, and cleansed the carpet. In the event that you’re not confident enough to tackle the problem on your own, you can always call in mold wall removal professionals. It is our hope that we have provided you with all of the knowledge you need to detect mold in your walls.

Helen Skeates

Helen Skeates

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