What Does Black Mold Look Like? Signs, Photos, and Dangers
What does black mold look like? Black mold (Stachybotrys chartarum) looks dark green to black, slimy when actively growing and powdery when dry, and it grows on wet cellulose materials like drywall, wood, and paper. Color alone cannot confirm the species, so only a lab test names it. If you see it, do not disturb it. Fix the water source, wear an N95 mask, gloves, and goggles, and call a professional for areas larger than 10 square feet.
Dealing with a different color? See the guides to orange mold, yellow mold, and white mold.
Black mold at a glance
This page is the full guide to black mold. It covers what it looks like, how to tell it apart from look-alikes, the stages it moves through, where it hides, whether it is dangerous, and how to clean it. The quick answers are below, and each one links to a deeper guide if you want more detail on that single question.
- Appearance and color: dark green to black, slimy when wet and powdery when dry. Jump to the full breakdown of what does black mold look like, including color, sheen, and texture.
- Identifying it: check color, texture, smell, and location, then run a wipe test. The step-by-step method is in our guide on how to identify black mold.
- Is it dangerous: indoor mold can cause stuffy nose, coughing, and wheezing, with stronger reactions in sensitive people. What the evidence actually shows is in is black mold dangerous.
- Mold or mildew: mildew is flat and wipes off, black mold grows deeper and comes back. We compare them in .
What does black mold look like?
Black mold is dark greenish-black with a slimy or wet appearance when actively growing. When it dries out, it becomes powdery and grayish. It grows in patches that spread outward from a central point. Unlike common bathroom mildew (which is flat and gray-white), black mold has a fuzzy or hairy texture you can see up close. It prefers paper-backed drywall, ceiling tiles, wood, and cardboard. It needs constant moisture to survive, so you will almost always find a water source nearby. For the full breakdown of color, sheen, and texture, see our guide on what black mold looks like, and compare it against our guide if you think you might be looking at surface mildew instead.
How to identify black mold
Run through five clues before you call anything black mold. Color: dark green to black, sometimes gray or olive at the edge. Texture: slimy while growing, powdery or speckled once dry. Shape: irregular blotches, rings, or scattered dots, not a clean line. Smell: a musty, earthy odor that gets stronger up close. Location: it sits where water lingers.
No single clue is proof. The CDC is clear that you cannot tell a mold is hazardous, or even which species it is, by how it looks. A simple wipe test helps: dirt and soot smear and lift off a hard surface, while mold clings, leaves a stain, and grows back because it roots into porous material. For the full step-by-step method, read our guide on how to identify black mold.
The stages of black mold growth
Black mold moves through clear stages, and catching it early makes cleanup far easier.
Stage 1, surface film: a damp surface stays wet for more than a day or two and a thin, flat film begins. At this point it often reads as mildew, flat and easy to wipe. This is the easiest stage to stop.
Stage 2, active colony: the growth turns dark green to black, looks slimy or glistening, and spreads outward in blotches. It now has roots in the material and returns after a surface wipe.
Stage 3, established and dry: the colony matures, dries to a powdery or speckled patch, and can release spores when disturbed. The material underneath, like paper-backed drywall, may be softened and need replacing.
If you are not sure whether you are at the mildew stage or a deeper colony, our guide walks through the wipe test that separates them.
Where does black mold hide in your home?
Bathroom: Behind shower walls, under sinks, around toilet bases, exhaust fan covers. The shower ceiling directly above the showerhead is the number one spot.
Basement: Lower walls where foundation moisture wicks up. Floor corners and cracks where water seeps through. Behind stored boxes sitting on concrete.
Kitchen: Under the sink (supply lines and P-trap drips), behind the fridge drip pan, dishwasher door seal.
Bedroom: Closet ceiling corners (dead air + cold exterior wall), wall behind the headboard, underside of the mattress.
HVAC: Inside air ducts, on the evaporator coil, around supply register ceiling halos. If mold is in your HVAC, every room in the house is exposed.
Attic: Underside of roof sheathing, especially with poor ventilation.
Is black mold dangerous?
According to the CDC, being around damp, moldy indoor spaces can cause stuffy nose, throat irritation, coughing, wheezing, and itchy eyes or skin, with stronger reactions in people who have asthma or a mold allergy. The CDC is also direct that you cannot tell whether a mold is hazardous by its color or look, so the response to any indoor mold is the same regardless of color.
The dramatic claims about toxic black mold tend to outrun the evidence, especially for healthy adults. For what the science actually supports, who is most at risk, and how to weigh the fear against the facts, read our full guide on is black mold dangerous. If you or someone in the home has ongoing symptoms, see a physician.
How to get rid of black mold
If the area is smaller than 10 square feet:
1. Fix the water source first. No point cleaning mold if water keeps feeding it.
2. Wear an N95 mask, gloves, and goggles. Do not breathe the spores.
3. On hard surfaces (tile, concrete): spray with a no-bleach mold-control product, let it dry fully (4 to 24 hours), scrub, repeat.
4. On drywall: if the mold has penetrated through the paper backing, cut out the affected section plus 12 inches beyond visible growth and replace.
5. Seal with a stain-blocking primer (for concrete) or mold-resistant paint (for drywall) after cleaning.
6. Run a HEPA air purifier during and after remediation.
7. Keep humidity below 50% with a dehumidifier.
NEVER use bleach. Bleach does not kill mold roots on porous surfaces. It adds moisture. Every leading mold expert agrees on this.
If the area is larger than 10 square feet: Hire a qualified mold remediation professional (one who follows the IICRC S520 standard; ACAC or RIA credentials and state licenses count too). Make sure the inspector is independent from the remediation company (conflict of interest). The average professional mold remediation costs $1,500 to $5,000 depending on the extent.
How to test for black mold
The best test is an ERMI (Environmental Relative Moldiness Index) or HERTSMI-2, which analyzes dust samples for DNA of 36 mold species. This is far more accurate than air sampling (mold spores fall to the floor, so air tests miss them).
For body testing, a urine mycotoxin panel from a specialty lab measures trichothecenes and other mycotoxins being excreted by your body.
Or you can start with our free app: Mold Scanner AI scans 160 professional hotspots with your phone camera using the same checklist professional mold inspectors follow.
Scan your home with Mold Scanner AI
Our app walks you through 160 professional mold hotspots room by room. Same checklist professional mold inspectors use. AI-powered verdict in 30 seconds.
Get Early AccessReal black mold photos
Real, unedited photos of black mold in homes: bathrooms, walls, ceilings, windows, and furniture. Compare them against what you are seeing. Color alone never confirms the species, only a lab test does.
Frequently Asked Questions
Can black mold kill you?
For most healthy people, household black mold is not directly lethal, and the CDC links indoor mold mainly to respiratory symptoms like stuffy nose, coughing, and wheezing. People with weakened immune systems, infants, and older adults can react more strongly. If you have symptoms, see a physician.
What is the difference between black mold and regular mold?
Not all dark-colored mold is Stachybotrys (true black mold). Common dark molds include Cladosporium (low risk) and Aspergillus (moderate risk). Stachybotrys specifically requires constant moisture and cellulose to grow. Lab testing (ERMI) is the only way to confirm the species.
Does bleach kill black mold?
No. Bleach kills surface mold on non-porous surfaces like tile but cannot penetrate porous materials like drywall or wood where mold roots grow. It also adds moisture, which feeds regrowth. Use a mold-control product, hydrogen peroxide, or physical removal instead.
How much does black mold removal cost?
DIY removal for small areas costs $50 to $200 in supplies. Professional remediation for larger areas typically runs $1,500 to $5,000. Full-home remediation with HVAC cleaning, containment, and post-testing can reach $10,000 to $30,000 for severe cases.
Sources
- CDC: Basic facts about mold and dampness. Centers for Disease Control and Prevention.
- EPA: A brief guide to mold, moisture, and your home. US Environmental Protection Agency.
- WHO Guidelines for Indoor Air Quality: Dampness and Mould. World Health Organization, 2009.
- Mudarri D, Fisk WJ. Public health and economic impact of dampness and mold. Indoor Air, 2007.
- ANSI/IICRC S520: Standard for Professional Mold Remediation. Institute of Inspection, Cleaning and Restoration Certification.
- HUD Healthy Homes: Mold Resource Book. US Department of Housing and Urban Development.
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