What Causes Mold in Homes—and How to Prevent and Remove It Safely

By Adam Bakonis and the Mercury Team

No homeowner wants to find mold. Those fuzzy spots or dark patches can show up anywhere, sometimes hiding in plain sight, other times spreading quietly behind walls. While it may seem minor at first, mold can cause lasting damage and even health problems if ignored.

Let’s look at what mold really is, what makes it grow, and what you can do to prevent and remove it safely.

What Does Mold Look Like and Why Does It Matter?

Mold can take on different colors and textures (black, green, white, or even orange), and it can appear fuzzy, slimy, or speckled. It thrives in damp, poorly ventilated areas, such as:

• Bathrooms: Around tubs, sinks, and tile grout.
• Basements and crawl spaces: Especially after heavy rain or plumbing leaks.
• Kitchens: Near sinks, dishwashers, or behind refrigerators.
• Attics: Often caused by roof leaks or poor insulation.

Mold matters because it can damage your property by eating away at drywall, wood, and other organic materials. It also releases tiny spores into the air that may cause coughing, sneezing, or asthma flare-ups, so it’s best to take care of mold as soon as you spot it.

What Causes Mold Growth Indoors

Mold needs only a few things to grow: moisture, a food source (like drywall or wood), and the right temperature. Since most homes provide the food and temperature, moisture is the key factor that homeowners can control.

The Role of Moisture and Humidity

Moisture is the main factor behind indoor mold growth. When humidity levels stay high, it creates the perfect conditions for mold spores to spread and thrive.

Common sources of moisture include:

• Leaks: Slow drips from pipes, roofs, or windows can saturate walls and floors.
• Condensation: Water droplets can form on cold surfaces like windows, pipes, and concrete walls, especially in winter.
• Poor ventilation: Steam from cooking or showering can get trapped in bathrooms and kitchens, raising humidity levels.
• Flooding: Major water events, like floods or burst pipes, can lead to widespread mold if not dried out quickly.

Hidden Problem Areas

Sometimes, the biggest mold problems are the ones you can’t see. Mold can flourish in hidden areas, making it difficult to detect until it has spread. Be aware of these common hiding spots:

• Behind drywall and wallpaper
• Underneath carpets and flooring
• Inside HVAC ducts and vents
• Above ceiling tiles

A lingering musty smell, dark stains on walls, or bubbling paint can all point to hidden growth. If these warning signs sound familiar, schedule a home inspection to help catch mold before it causes costly damage.

How to Prevent Mold from Growing in Your Home

Prevention is the most effective and cost-efficient way to avoid mold problems. Following a routine home maintenance checklist can help keep your home dry and mold-free. Take a look at this step-by-step guide on how to stop mold from growing in your home.

Step 1: Control Moisture Levels

Since moisture is the main ingredient for mold, keeping your home dry is key.

• Use dehumidifiers in damp areas, such as basements, to keep humidity levels below 50%.
• Run exhaust fans in bathrooms and kitchens to vent steam and moisture outside.
• Address any leaks from plumbing or your roof immediately. Dry all wet areas within 24-48 hours to prevent mold from taking hold.
• Consider installing leak detection systems, which can alert you to a problem before significant damage occurs.
• Consider installing a humidity monitor in high moisture areas.

Step 2: Improve Air Circulation

Good airflow helps prevent damp, stagnant areas where mold thrives. 

• Open windows whenever possible to allow fresh air to circulate.
• Make sure furniture isn’t blocking air vents.
• Clean and replace your HVAC filters regularly to ensure your system runs efficiently.

Step 3: Maintain Your Home’s Structure

Regular checkups give you peace of mind and help you stay ahead of potential home maintenance problems.

• Examine your roof, plumbing, and foundation for any cracks or signs of water intrusion.
• Check the caulking and grout around showers, tubs, and sinks, and reapply it as needed to prevent water from seeping into walls.

Step 4: Clean and Disinfect Regularly

Keeping surfaces clean can discourage mold growth.

• For small spots of surface mold, a solution of vinegar and water or a bleach-based cleaner can be effective.
• Always ensure proper ventilation when using cleaning products, and never mix different agents (especially bleach and ammonia), as this can create toxic fumes.

How to Treat Household Mold Safely

If you find mold in your home, your approach to cleaning it will depend on the size of the problem.

When You Can DIY

You can typically handle small mold problems yourself if the affected area is less than 10 square feet and is on a hard, non-porous surface. Here’s what you should do:

• Wear protective gear: Always use an N95 mask, safety goggles, and rubber gloves to protect yourself from mold spores.
• Clean the surface: Scrub the moldy area with a stiff brush using a solution of soap or detergent and hot water.
• Disinfect: After cleaning, wipe down the area with a bleach and water solution (1/2 cup of bleach per gallon of water) and let it air dry completely.

When to Call a Professional

Some mold situations are too extensive or dangerous to handle on your own. It’s time to call a licensed mold remediation specialist if:

• The mold covers a large area (more than 10 square feet).
• Mold is growing behind walls, under floors, or inside your HVAC system.
• Your home has experienced significant water damage from flooding or a sewage backup.
• Someone in your household has a compromised immune system or severe allergies.

Avoid These Common Mistakes

When dealing with mold, what you don’t do is as important as what you do.

• Don’t paint or caulk over mold. This only hides the problem and allows the mold to continue growing underneath.
• Don’t use a fan to dry a moldy area. This can spread mold spores to other parts of your home. The area must be cleaned and disinfected first.

Insurance and Mold Damage: What’s Covered?

Whether your homeowners insurance covers mold damage depends on the cause of the problem.

Does Homeowners Insurance Cover Mold?

Most homeowners policies cover mold if it results from a sudden, covered event, such as a burst pipe or storm-related leak. However, mold from ongoing leaks or neglect is usually not covered.

“Insurance is designed to cover sudden and accidental events, not gradual wear and tear,” explains Adam Bakonis, Sr. Product Manager, State for Mercury Insurance. “If mold is caused by something like a plumbing leak that wasn’t repaired, it’s usually not covered. That’s why regular maintenance is so important.”

When in doubt, review your policy or contact your local agent for clarification.

Mercury’s Protection Options

Mercury offers several optional coverages that can help prevent the types of water damage that lead to mold.

Our Service Line Protection covers underground pipes and wires, while Home Systems Protection helps cover breakdowns of key home systems, including HVAC and water heaters.

If you discover mold resulting from an insured event, you should file a claim as soon as possible. Your agent can walk you through the process and explain your coverage options.

Final Thoughts: Keep Your Home Dry, Clean, and Protected

The key to keeping mold away is staying proactive. Control humidity, maintain good airflow, and fix leaks as soon as they appear. It’s also smart to schedule seasonal home inspections, especially before winter or rainy months.

Protecting your home is easier when you have the right insurance partner. Mercury offers affordable, dependable homeowners coverage to help you handle life’s unexpected surprises.

Contact us today for a fast, free quote!