A mold infestation is one of the most dreaded home problems. Mold exposure can cause or worsen respiratory illness, and it’s often a sign of more serious damage to your house. Mold is scentless and silent, so it can linger for a long time without discovery. If you suspect you may have mold, you must address the problem promptly—but getting a professional mold inspection might not be necessary. 

Here, we’ll explore common indicators, hidden mold threats, and preventive measures to help keep your home mold-free. We’ll also offer recommendations for when you do and don’t need professional mold inspection or remediation.

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Understanding Mold and Its Growth Conditions

Before tackling mold, it’s a good idea to understand what it is and where it comes from.

What Are Molds?

Molds are fungi, a type of organism that is essential to life as we know it. Their primary purpose is to recycle dead organic matter to release carbon, oxygen, and minerals into the environment. Making bread, beer, and wine requires yeast, a type of fungus. The antibiotic penicillin was originally derived from a species of mold. Mushrooms are a great addition to many meals.

However, there’s a difference between the edible fungi in nature and the mold that grows in your home. When mold grows indoors, it can cause health issues and property damage. While the health risks associated with mold are sometimes exaggerated, according to the Environmental Protection Agency (EPA), it’s especially harmful to young children, the elderly, people with allergies, and those with preexisting respiratory conditions such as asthma.

Here are some of the known health hazards of living in a building with mold:

• Asthma attacks
• Dizziness
• Headaches
• Red eyes
• Runny nose
• Skin rashes
• Sneezing

Thus, it’s always a good idea to address a home mold problem, no matter how small it initially seems.

Factors That Promote Mold Growth

Mold growth occurs when mold spores settle on a surface with appropriate food sources, the right temperature, and the ideal moisture amount.

1. Food sources: Many household materials provide nutrients for mold, including wood, paper, drywall, clothing, leather, and dirt. These materials, when exposed to moisture, can be a breeding ground for mold.
2. Moisture: This is the most critical factor and the one you can control. Excess moisture from leaks, high humidity, or poor ventilation creates ideal conditions for mold growth. Other obvious sources are floods, roof leaks, indoor water leaks, and drainage or plumbing problems. 
3. Temperature: Mold grows best between 60 and 80 degrees Fahrenheit, which unfortunately coincides with comfortable indoor temperatures for humans. This overlap means that mold can grow unnoticed in your living space if other conditions are met.

While you can mitigate some of these factors, you can never remove them completely. However, by reducing excess moisture, you can reduce or even eliminate a mold problem.

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Common Signs of a Mold Problem

Recognizing the signs of mold growth early can help you address the issue before it becomes a major problem. Because a mold problem is also a moisture problem, it‘s wise to be on the lookout for these telltale signs. 

• Buckling wood floor coverings, including wood-based laminates: Excess moisture, improper installation, or a combination of both can cause buckling.
• Deteriorated wood (especially in a crawl space): You’re most likely to find deteriorated wood around the perimeter of your home’s foundation and below the bathrooms and kitchen. Rotten wood will usually appear dark and allow a sharp object, such as an ice pick or screwdriver, to penetrate it with little effort. The wood may even have visible fungi growing on it. Be careful when entering a deteriorated crawl space; it may be dangerous. 
• Efflorescence: Efflorescence is a white powder on brick, concrete, and block foundation walls. It‘s a mineral residue left when water seeps through the walls and dries—evidence of a moisture problem.
• Loose, peeling, or stained wallpaper: Moisture can collect behind wallpaper, and the wallpaper and glue can provide mold with food. This situation is most common in air-conditioned homes in warm and humid climates, but it can also occur in other climate zones.
• Musty smell: You’ll often smell mold even if you can’t see it since it gives off an odor as it breaks down its food. This odor is usually described as damp, stale, earthy, or sour, but some mold may be more pungent. The stronger the smell, the more serious the problem.
• Signs of water damage: Water stains often appear as light brown areas. Common places to find water stains include around windows and doors, on ceilings below attics and bathrooms, on ceilings around fireplaces and woodburning stoves, and below where a deck attaches to the house. Make sure to check closet ceilings as well.
• Stains on vinyl floor coverings, especially above a crawl space: These stains occur on floor coverings for the same reasons as on wallpaper.
• Visible mold growth: Home mold appears in many colors, the most common being green, white, and black. Fungi can appear in different colors within the same infestation and at different times. Color depends on species, light, moisture level, and food type. Mildew, a type of fungi, can appear in areas of low air circulation and high humidity, such as bathrooms and closets.

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Finding Hidden Mold

Mold doesn’t always grow in plain sight. If you smell mold or spot other signs but can’t find the mold itself, try these locations and methods.

Potential Hidden Mold Locations

Mold often thrives in dark, damp areas that aren’t regularly inspected. Common hiding spots include:

• Behind wallpaper or drywall, where moisture can be trapped
• Under carpets or floorboards, especially in areas prone to moisture
• Inside air ducts, which can spread spores throughout your home
• Around plumbing fixtures, where leaks are common
• In attics or crawl spaces that are poorly ventilated

Check these locations with a flashlight, but be sure to wear a dust mask to protect yourself from spores.

Using Moisture Meters and Infrared Cameras

Professional inspectors often use specialized tools to detect hidden moisture and mold. Moisture meters measure moisture levels in materials, helping identify potential mold growth areas. Infrared cameras detect temperature differences that may indicate moisture buildup behind walls or ceilings. While professionals primarily use these tools, some homeowners opt to purchase moisture meters for regular home maintenance.

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Professional Mold Inspection and Testing

According to the EPA, most of the time, professional mold inspection and testing aren’t necessary. If you see mold, you have mold, and the EPA recommends that you treat all types of mold as health hazards and clean them up promptly. 

On the other hand, there are a few situations where a professional home inspection can be helpful. Professionals have training and equipment that helps them identify trouble sources and growth patterns, and they’ll often provide you with a written report, including recommendations for fixes. Here’s when it’s a good idea to hire a pro:

• After water damage or flooding: Stormwater, burst pipes, roof leaks, and sewage backups can lead to extensive mold growth within 24–48 hours if you don’t address them immediately. If you weren’t able to dry out your home promptly after one of these events or if the flooding was severe, consider a professional inspection.
• Persistent musty odors: If you’ve cleaned repeatedly and still smell mold, you may not have found the source. These odors often indicate hidden mold growth that requires expert detection and remediation.
• Unexplained health issues: When family members experience the health problems described above but improve when they’re away from home, mold could be the culprit.

Note that even in these situations, test kits aren’t necessary. The Centers for Disease Control and Prevention (CDC) doesn’t distinguish between the different types of mold in terms of health risks. A mold inspection helps you locate and fix the problem, not identify the type of mold.

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Dealing With a Mold Problem

Once you find mold, you then need to decide what to do about it. Usually, this involves tackling the underlying moisture problem before you start cleaning up the mold itself, otherwise the mold may simply regrow. It’s difficult, if not impossible, to remove all mold spores from a location. You’re better off reducing the factors that make mold growth possible first.

Taking Safety Precautions

When removing and disposing of mold or moldy objects, always wear gloves to protect your skin and a mask to protect your lungs. Unventilated goggles will protect your eyes from mold spores. If the problem is extensive or you know you’re sensitive to mold, use an N95 mask or respirator. Don’t touch moldy items with bare hands.

You should also recognize when the problem is too big for you to tackle on your own. The EPA advises homeowners dealing with more than 10 square feet of mold to hire a professional abatement team. Professional remediation is also recommended for mold in a building’s HVAC system or mold after a sewage flood. Check out our mold remediation cost guide for more information.

Finding Moisture Sources

You’ll first need to determine the source of the excess moisture in your home. Sometimes, this is easy. Many times, however, it can be complicated. If you can’t find the source, hire an experienced, licensed contractor or home inspector. Here are some common moisture sources:

• Clothes dryer exhaust systems: Keep your dryer exhaust system clean and in good repair. Look for crimps in ducts (especially the transition duct between the dryer and the duct connection point), disconnected ducts, and excess lint behind the dryer and at the duct termination point. A restricted or disconnected clothes dryer exhaust duct can cause moisture problems and be a fire hazard, as lint is very flammable.
• Condensation and poor airflow: Condensation on and around windows can be a nuisance and cause damage over time. Try to keep the relative humidity in the house below about 50%. A dehumidifier may help during the summer. Poor airflow in bathrooms and closets seldom causes a significant mold problem. Still, we recommend wiping down shower walls after use and running the exhaust fan during and at least five minutes after showering. A moisture absorber may be helpful in closets.
• Flooding, sewage backups, and other contaminated water: Sewage backup spreads bacteria and releases toxic gas such as hydrogen sulfide. Stormwater flooding is also contaminated by sewage, gasoline, oil, and industrial chemicals. Qualified contractors should deal with mold and damage caused by these situations.
• Grade, drainage, gutters, and downspouts: Poor landscape grading, insufficient drainage, clogged gutters, and leaky downspouts cause water to pool around a foundation and often seep into a basement. Soil should slope away from the foundation at least 6 inches within the first 10 feet from the foundation. Hard surfaces, such as stoops, patios, and driveways, should slope at least one-fourth-inch per foot away from the foundation. Keep gutters clean, in good repair, and sloping toward the downspouts. Discharge downspouts at least 5 feet away from the foundation.
• Heating and air conditioning system (HVAC): Mold can clog or contaminate HVAC components. Mold is especially common on the evaporator coil at the air handler or furnace because this coil is always wet when the air conditioner is operating. Mold can also contaminate the air ducts. Most people should hire a qualified contractor to determine mold contamination in their HVAC system.
• Kitchens and bathrooms: Cooking and bathing can add more moisture than you think to your home. Use kitchen and bathroom exhaust systems to remove excessive moisture.
• Plumbing leaks: Leaks in water supply pipes are easier to find if you see or hear the water constantly flowing. Slow leaks are more difficult to spot in walls and foundation slabs, the riser between a shower valve and the shower head, and at joints between pipe sections. Leaks in drainage pipes and leaks at plumbing fixtures, such as toilets, can be challenging to find because the water only flows when fixtures are in use. Call a plumber if you suspect a leak but can’t pinpoint the origin.
• Roof leaks: Roof leaks are often very difficult to find because the leak itself can occur far from where the water damage is visible. Leaks commonly occur at roof penetrations, such as chimneys, appliance vents, and plumbing vents. Improperly installed and deteriorated flashing is another common cause of leaks. Most people should hire a qualified roofer to find and fix roof leaks and consider getting a roof protection warranty plan.
• Wall leaks: Water leaks through walls at wall penetrations: doors, windows, pipes (e.g., hose bibbs), and exhaust vents (e.g., clothes dryers and bathroom ventilation fans). Leaks occur when the flashing or caulking around these penetrations is improperly installed or begins to deteriorate. Poor stucco and siding installation can also let water in. Most people should hire a qualified contractor or home inspector to find and fix wall leaks and consider investing in quality replacement windows.

Cleaning and Removing Mold

With moisture problems mitigated, you can begin to clean or remove moldy materials—a process called mold remediation or abatement. Here’s how to deal with various types of materials.

• Cleaning mold from undamaged hard materials: You may be able to clean mold from accessible hard materials with less than 10 square feet of mold coverage. Use detergent and water according to the detergent manufacturer’s instructions. Always test a small area first to avoid damaging the material.
• Cleaning mold from soft or absorbent materials: Cleaning mold from soft or absorbent materials is often difficult or impractical. Mold can hide inside these materials, so surface cleaning may not remove the mold altogether. You should discard porous materials that you can’t launder, such as carpet and drywall.
• Dealing with mold on damaged materials: You should remove and discard moldy materials that have damage. Mold-infested materials may qualify as hazardous waste, so you must comply with state and local mold removal and disposal regulations, including hiring a qualified mold remediation contractor.

After you clean, allow all materials to dry completely before painting, caulking, or doing any other repairs or renovations. Note also that mold may cause staining that can’t be completely removed.

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The Bottom Line: Should I Get a Mold Inspection or Test?

Mold testing, inspection, or sampling is usually unnecessary, especially if you can see or smell mold. If that’s the case, start cleaning. However, it’s time to hire an inspector if you can’t find a mold problem but suspect it may exist.

Mold is everywhere, but it becomes a problem when we allow excess moisture in our homes. Find and fix the sources of the moisture, and you’ll seldom have a serious mold problem. If you don’t, the mold may return and damage your home and potentially your health. The risks are particularly serious for those with allergies or asthma.