Mold in Your House: How to Spot It, Test It and Get Rid of It

What Causes Mold in a House?

Mold in a house almost always means a moisture problem: a leak, high humidity or poor airflow. Look for musty smells, spots on ceilings, walls or vents, and water stains. Small patches on hard surfaces can be cleaned; anything larger than about 10 square feet, inside walls or in the HVAC system needs testing and professional remediation.

Mold spores float in every home and grow when they land on something damp, like drywall paper, wood, dust or carpet. The University of Georgia Extension puts it simply in its 2023 Mold and Moisture Home Inspection Checklist: mold spores need only a comfortable environment, food and moisture to grow. You cannot take away the food or the temperature in a lived-in house. You can take away the water.

That is why the EPA, in A Brief Guide to Mold, Moisture and Your Home, says the key to mold control is moisture control. In the homes we inspect, the water almost always comes from one of six places:

• Roof and plumbing leaks. A slow drip under a sink, a leaking supply line or a roof flashing gap that wets the attic every storm.
• High indoor humidity. The EPA says to keep indoor humidity below 60 percent, ideally between 30 and 50 percent. Above that, mold can grow on surfaces that never get wet.
• Condensation. Warm, damp air hits a cold window, wall, pipe or duct and turns to water.
• Vented crawl spaces and basements. Damp soil and outside air keep the space under the house wet for months.
• Bathroom and laundry moisture. Showers without a working fan and dryers that are not vented outside.
• Past water damage that was not fully dried. The EPA says water-damaged areas should be dried within 24 to 48 hours to prevent mold growth. Wet drywall that only looks dry on the surface is a common source.

Why North Atlanta Homes Get Mold

Georgia gives mold a head start. Our summers are long and humid, so the air itself carries a lot of water for months at a time. Many homes in Gwinnett, Forsyth and North Fulton sit on vented crawl spaces over red clay that holds water after every rain, and that damp air rises into the floors above. Many also run ductwork through hot attics, where cold supply ducts sweat in summer.

In a lot of the North Atlanta homes we inspect, the mold the homeowner noticed is not the first mold in the house. It is just the first spot they could see. The source is usually one level down in the crawl space or one level up in the attic. If humidity is the root cause, a whole-house or crawl space dehumidifier that holds 45 to 50 percent does more than any amount of scrubbing.

What Are the Signs of Mold in Your House?

Mold does not always show itself as a black patch. The CDC notes that mold can look like spots of many different colors and can smell musty. These are the 10 signs of mold in a house we see most often:

1. A musty, earthy smell. Often the first sign, and often strongest in closets, basements or right after the system kicks on.
2. Visible spots. Black, green, gray, white or brown speckles on ceilings, walls, grout or wood.
3. Water stains. Yellow or brown rings on a ceiling or wall mean water has been there, and mold may be behind it.
4. Peeling, bubbling or cracking paint. Moisture pushing through drywall lifts paint and wallpaper.
5. Condensation. The EPA calls condensation a sign of high humidity. Fogged windows and sweating pipes feed mold nearby.
6. A damp crawl space or basement. Wet soil, wet block walls or a heavy damp smell under the house.
7. Dust or dark spots at supply vents. Spotting on the ceiling or wall around a vent can be mold, not just dust.
8. Warped or soft floors. Cupped wood or soft spots near a bathroom, kitchen or crawl space point to long-term moisture.
9. Mildew on fabric and stored items. Shoes, clothes, boxes and furniture in closets that come out spotted or smelling sour.
10. A smell that comes with the AC or heat. If the musty smell shows up when the system runs, the air handler, coil or ducts may be involved.

For a full walk-through of each one, read our guide to the signs of mold in your house, and if the smell is your main clue, start with how to find the source of a mold smell.

Pay close attention to mold around vents and windows. Mold there usually points to condensation, a window leak or moisture moving through the duct system.

Where Does Mold Hide in a House?

The EPA lists the back side of drywall, wallpaper and paneling, the underside of carpets and pads, and the inside of ductwork as places mold can hide. Here is where we find it most in North Atlanta homes, what you will notice, what usually causes it and who should fix it.

Bathrooms are the most common place homeowners spot mold first, and the most common place it keeps coming back. Our guide to mold on the bathroom ceiling explains why. Attics are a close second in our area, covered in mold in the attic.

Mold in the HVAC system deserves its own warning. The EPA says not to run the HVAC system if you know or suspect it is contaminated with mold, because running it could spread mold through the house. If you see spots around several vents or smell mustiness every time the system starts, read mold in air ducts and have it checked before you keep running it. After the moisture is fixed, duct sanitizing cleans and deodorizes the lines.

Is It Mold or Mildew?

Mildew is a type of mold that stays on the surface. People use the word for the light, powdery growth on shower grout, window sills and fabric. Mold is the broader name, and it is the growth that roots into soft materials like drywall, wood and carpet. Here is how to tell them apart at a glance:

Is Black Mold Worse Than Other Mold?

"Black mold" is the name people give to any dark mold. The CDC describes Stachybotrys chartarum, the mold most people mean, as a greenish-black mold. But plenty of common molds are dark too, so color alone cannot tell you the type.

The more useful point is this: the CDC says all molds should be treated the same with respect to potential health risks and removal, and that no matter what type of mold is present, you need to remove it. If mold is growing inside your home, remove it and fix the moisture that let it grow.

On health, we stick to what the EPA and CDC say. The EPA notes that allergic reactions to mold are common and that mold can cause asthma attacks in people with asthma who are allergic to mold. The CDC says damp and moldy homes may cause a variety of health effects, or none at all, and that people with asthma or mold allergies may react more strongly. If anyone in your home has health concerns, talk with a doctor, and let us know before we start so we can plan the work around them.

Mold Testing or Mold Inspection: Which Do You Need?

A mold inspection finds the moisture and the growth. We look at ceilings, walls, windows, closets, the crawl space or basement, the attic where we can reach it, and the vents and air handler. We take moisture meter readings on the materials themselves, because a wall can look dry and read wet.

Mold testing takes samples. Air or surface samples help when mold is suspected but not visible: a musty smell with no spots, a past leak inside a wall, a family member reacting to one room, or a home sale where a buyer or seller wants it in writing.

Here is the honest part. The EPA says that in most cases, if visible mold growth is present, sampling is unnecessary. If you can see it, you already know it is there, and what you need is an inspection that finds the moisture and maps how far it spreads. Testing earns its place when the question is "is there mold I cannot see?"

The moisture meter is the tool that answers the question most homeowners actually have, which is "why is this happening?" A reading on a ceiling joist or a wall cavity tells us whether a leak is still active or old and dry, and whether the problem is a leak, condensation or humidity. That decides the fix. Cleaning mold without that answer is how it comes back.

Our mold testing and inspection covers both, and we are open 24/7 with same-day appointments. To see what goes into it, read how to test for mold in your house and our side-by-side guide to mold testing vs mold inspection. If you also want to know what else is in the air, air quality testing measures particles, humidity, VOCs and CO2.

How Do You Get Rid of Mold in a House?

How to get rid of mold in a house depends on how much there is, what it is growing on and where. Every job, big or small, has the same two parts: remove the mold and fix the water.

When You Can Clean It Yourself

The EPA says that if the moldy area is less than about 10 square feet, roughly a 3 foot by 3 foot patch, you can usually handle the cleanup yourself. That applies to hard surfaces like tile, glass, sealed wood and painted trim.

1. Fix the water first. Stop the leak, run the fan or dry the area, or the mold will come back.
2. Gear up. The EPA recommends an N-95 respirator that fits properly, long gloves that reach mid-forearm and goggles without vent holes.
3. Scrub with detergent and water. The EPA's cleanup advice for hard surfaces is to scrub mold off with detergent and water and dry completely.
4. Dry it fully. Use fans or a dehumidifier until the surface is dry to the touch and stays dry.
5. Bag and toss what will not clean. The EPA says absorbent materials like ceiling tiles and carpet may have to be thrown away if they become moldy.

When to Call a Professional

• The mold covers more than about 10 square feet.
• It is inside walls, ceilings or under floors.
• It is in the HVAC system, ducts or air handler.
• The water came from sewage or flood water.
• It keeps coming back after you clean it.
• Someone in the home has asthma, allergies or other health concerns.

What Professional Mold Remediation Includes

Our mold remediation follows the same steps every time:

1. Containment. We seal off the work area so spores stay where they are.
2. HEPA-filtered air scrubbers. Negative air pulls spores out of the work area and through HEPA filters.
3. Removal of damaged materials. Moldy drywall, insulation, carpet pad and other porous materials come out.
4. Cleaning and drying. Hard surfaces are cleaned and the area is dried with air movers and dehumidifiers.
5. Fixing the moisture source. We find what fed the mold and fix it or tell you exactly who should, so the job holds.

How Do You Keep Mold From Coming Back?

Mold comes back when the moisture comes back. The EPA notes that a background level of mold spores will always remain in a home, but those spores will not grow if the moisture problem has been resolved. Prevention is about keeping things dry.

• Hold humidity at 45 to 50 percent. The CDC says to keep indoor humidity no higher than 50 percent all day long. In a Georgia summer that usually takes a whole-house or crawl space dehumidifier, not just the AC.
• Dry leaks within 24 to 48 hours. That is the EPA's window. For anything bigger than a towel can handle, call 24/7 water damage mitigation for extraction, drying and moisture checks.
• Run bath and laundry fans. Run the bath fan during and after every shower, and make sure the dryer vents outside, not into the attic or crawl space.
• Clean and inspect your ducts. Keep the coil and drain pan clean so the air handler does not stay wet, and sanitize ducts after any mold problem.
• Encapsulate or dehumidify the crawl space. The UGA Extension checklist says the crawl space soil should be covered with at least a 6 to 8 mil plastic vapor barrier. Full crawl space encapsulation goes further and seals the space from wet outside air.
• Keep gutters clear. Clogged gutters dump water at the foundation, and in red clay it stays there.

Humidity changes with the seasons here. Summer brings damp outside air, and winter brings cold walls and windows that collect condensation. Our guide to indoor humidity in Georgia covers the right level for each season. For cleaner air on top of dry air, UV lights and whole-home air purifiers help keep the coil and the air moving through it clean.

Mold Services From Fresh Cleaning Solutions

We are a locally owned air quality company in Suwanee, serving North Atlanta since 2016. One call covers the whole path, from finding the mold to keeping it gone:

• Mold testing and inspection, with real moisture meter readings
• Mold remediation, contained and HEPA-filtered
• Air quality testing
• Water damage mitigation, 24/7
• Duct sanitizing and odor removal
• Whole-house and crawl space dehumidifiers
• Crawl space encapsulation
• UV lights and air purifiers

We are NADCA and IICRC certified, open 24 hours a day, 7 days a week, and rated 4.9 stars from 501 Google reviews. Every job is a flat rate quoted up front with no hidden fees, backed by 100% satisfaction or your money back.

Seeing spots, smelling something musty or just had a leak? Call (678) 609-8713 or book a free estimate and we can often be there the same day.