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Moist mold and fungus in window and frame

Do I Have a Mold Problem?

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You may have mold issues if you’re a homeowner and have noticed a musty odor in your attic or basement or inexplicable residue on your walls. Here’s how to determine whether you need a mold inspection.

Default Author Icon Written by Angela Bunt Updated 06/06/2024

Mold infestation is one of the most dreaded home problems. Mold exposure can cause respiratory problems and have other negative health effects for you and your family. can cause respiratory problems and other negative health effects for you and your family. Mold is scentless and silent, so it can linger for a long time without discovery. If you suspect you may have mold, getting a professional mold inspection is crucial. Here, we delve into the signs of mold and when it’s time to get an inspection.

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Bathroom Mold Removal

Bathroom mold removal typically costs between $500 and $1,500.

Man Climbing Into Loft To Insulate House Roof
Attic Mold Removal

Removing mold from an attic costs $1,000–$9,000.

new basement has been insulated and waterproof
Basement Mold Removal

Basement mold removal projects typically cost $500–$4,000.


What Are Molds?

Molds are a member of the Fungi Kingdom along with yeasts, mildews, and mushrooms.

Fungi are 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. The antibiotic penicillin was originally derived from a species of mold. Mushrooms are a great addition to many meals.

There’s a difference between the edible fungi in nature and the mold that grows in your home. According to the Environmental Protection Agency (EPA), health risks associated with indoor mold growth include the following:

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

These risks are especially harmful to children, elderly people, and those with preexisting respiratory illnesses.

Why Does Mold Grow?

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

Remove any of these conditions, and mold will go dormant and often stop growing. Dormant does not mean dead, however. Mold will usually start growing again if the right conditions return.

Below, we elaborate on the conditions that allow mold to grow.


Many materials around homes provide food for mold, and there is no practical way to remove all these sources. Many are wood forms, including lumber, manufactured wood products such as plywood and fiberboard, and the paper on both sides of gypsum board (drywall). Clothing, leather, and dirt can also be food for mold.


Unfortunately, there’s no practical way to change the temperature to deal with mold. Mold grows best at temperatures between 60–80 degrees Fahrenheit, which is also ideal for human comfort.


Indoor mold growth indicates excess moisture and high humidity in your home. Design or construction defects, ineffective maintenance and repairs, and homeowner mistakes often cause it. Obvious sources are floods, roof leaks, indoor water leaks, and drainage or plumbing problems. 

Moisture is the only mold growth condition that we can control. Reducing excess moisture will reduce or eliminate mold problems.

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Signs of a Mold Problem

Because a mold problem is also a moisture problem, its wise to be on the lookout for the telltale signs. 

  • Buckling wood floor coverings, including wood-based laminates: Excess moisture, improper installation, or a combination 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. Deteriorated wood will usually appear dark and allow a sharp object, such as an ice pick or an awl, to penetrate it with little effort. The wood may even have visible fungi growing on it. Be careful when entering a crawl space; it may be dangerous. 
  • Efflorescence: Efflorescence is a white powder on brick, concrete, and block foundation walls. Its a mineral residue left when water seeps through the walls and dries.
  • Loose, peeling, or stained wallpaper: Exterior wallpaper can retain vapor. Moisture can collect behind the wallpaper, and the wallpaper and glue can provide mold food. This situation is more common in air-conditioned homes in warm and humid climates, but it can also occur in other climate zones.
  • Musty smell: Homes above crawl spaces and basements are especially susceptible to excess moisture infiltrating up from below. Areas with poor air circulation, such as closets, are susceptible to excess moisture. Placing an air conditioning supply outlet in a closet and properly closing a crawl space can help mitigate moisture. That said, closing a crawl space is a complex task you should leave to a qualified contractor. In most cases, you should keep the crawl space ventilation open.
  • 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 (be sure to look in closets), on ceilings around fireplaces and wood-burning stoves, below where a deck attaches to the house, and on ceilings below bathrooms.
  • 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.

How Do I Deal With a Mold Problem?

Dealing with a mold problem begins with solving the moisture problem. First, determine the source of the moisture and remediate it. Then, deal with the mold. Depending on the type of moisture problem, you may need to deal with it and the mold problem simultaneously.

Be careful when dealing with moldy materials. Some species of mold are toxic, and mold in sufficient quantities can produce health issues and allergic reactions, even in people who are not usually allergic to mold. Moldy materials may be considered hazardous waste, so specific removal and disposal procedures may be required. You may have to hire a professional mold remediator

Deal With Moisture Problems

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 can be 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 releases physical, airborne contaminants. Inhaling these vapors can lead to various health problems, including cramping, fever, and vomiting. Qualified contractors should deal with mold and damage caused by these situations.
  • Grade, drainage, gutters, and downspouts: Damp basements and crawl spaces are common sources of moisture problems. Poor grade, poor drainage, gutter issues, and problems with downspouts almost always cause these moisture problems. 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 system components. Mold is especially common on the evaporator coil at the air handler or furnace because it 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.
  • Kitchen and bathroom exhaust systems: Use kitchen and bathroom exhaust systems to remove excessive moisture. Cooking and bathing can add more moisture than you think to your home.
  • Plumbing leaks: Leaks in water supply pipes may be easy to find if you see or hear the water constantly flowing. Supply pipe leaks can be more difficult to find in walls and foundation slabs, the riser between a shower valve and the shower head, and slow leaks 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.
  • Roof leaks: Roof leaks are often very difficult to find because the roof leak can occur far from where the leak evidence is visible. Occasionally, roof leaks don’t cause mold and water stains on ceilings. The causes may be condensation, ice dams at eaves, or other problems. The most common leaks are at roof penetrations, such as chimneys, appliance vents, and plumbing vents. Improperly installed and deteriorated flashing is the most common cause of roof leaks. Most people should hire a qualified roofer to find and fix roof leaks.
  • Wall leaks: Wall penetrations are doors, windows, pipe penetrations (e.g., hose bibbs), and exhaust penetrations (e.g., clothes dryers and bathroom ventilation fans). Improperly installed and deteriorated flashing is a common cause of wall penetration leaks. Wrongly installed wall coverings, such as artificial stone and stucco, are also causes of wall leaks. Most people should hire a qualified contractor or home inspector to find and fix wall leaks and consider investing in quality replacement windows.

Clean Up and Remove Mold

Choosing to clean or remove moldy materials (mold remediation) depends on certain conditions. Here are some common situations:

  • 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. Avoid using chlorine bleach. While bleach may kill the mold, it probably will not remove it. Dead mold can cause allergic reactions, too. Cleaning larger hard materials yourself may be possible, but it will be more difficult and present more risks.
  • 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. In addition, cleaning may damage these materials.
  • Dealing with mold on damaged materials: You should remove and discard moldy materials that are also damaged. 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.

Mold Myths Busted

Let’s bust some of the many myths and misunderstandings about mold.

  • Mold is rare. Actually, mold is everywhere.
  • Mold is not a problem for many people. Mold can be a problem for people who are allergic to mold and have weak immune systems. Symptoms of allergic reactions to mold include a runny nose, watery or itchy eyes, and excessive sneezing. Fatigue, headaches, and breathing difficulties can occur in more severe cases. Ask your doctor about mold allergies.
  • Mold in your home is not a symptom of a potentially more serious problem. Mold requires moisture to grow, so the presence of mold in your home usually means excessive moisture. Excessive moisture can damage many materials in your home, requiring costly repairs and mold cleaning and removal (mold remediation).

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

Mold is everywhere and becomes a problem only when we allow excess moisture in our homes. Find and fix the sources of the moisture, and you will seldom have a serious mold problem. If you don’t, the mold may return, and damage to your home may occur.

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

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