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Cladosporium Mold: What It Is and Why It Grows in Your Home

Last updated October 25, 2026

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The short answer

What Is Cladosporium Mold

Cladosporium is a dark green or black mold that often appears as small spots or patches. It grows on surfaces that stay damp, including window frames, carpets, and wallboard. Unlike some molds that need constant wetness, cladosporium can survive on brief moisture, which makes it common in homes.

It does not usually cause serious illness, but it can trigger allergies or asthma symptoms in sensitive people. If you see it, you can clean small areas yourself with soap and water, but wear gloves and a mask. For larger growth, consider having a mold professional assess the situation.

Why It Grows in Your Home

Cladosporium needs two things: moisture and a food source. Wood, paper, and dust provide food, while humidity, condensation, or leaks supply moisture. Bathrooms, laundry rooms, and basements are common spots because they tend to be humid. Even a small roof leak or a damp crawl space can support growth.

In a mild marine climate with wet winters and dry summers, indoor humidity can rise during the cold months. Poor ventilation and uninsulated walls can create cold surfaces where moisture condenses. Fixing leaks and improving airflow are the first steps to stopping cladosporium before it spreads.

  • Check for leaks under sinks and around windows
  • Use exhaust fans in bathrooms and kitchens
  • Keep indoor humidity below 60 percent
  • Dry wet carpets and upholstery within 48 hours
  • Clean and repair roof gutters regularly
  • Wipe condensation off windows each morning

How to Identify Cladosporium

Cladosporium looks like dark green, brown, or black spots, often with a velvet or suede texture. It can grow on painted walls, tiles, grout, and even on leather or clothing. It often appears near windows where condensation collects, or on damp drywall after a leak.

You can sometimes tell it apart from other molds by its color and texture, but testing is the only sure way. If you are unsure, a mold professional can take a sample and identify the species. Knowing what you are dealing with helps you choose the right cleaning method.

Health Risks and Safety Steps

For most people, cladosporium is not a health threat, but it can irritate eyes, skin, and lungs. People with asthma or allergies may have stronger reactions. If you feel unwell after cleaning or exposure, see a doctor. Keep children and pets away from moldy areas while you work.

When cleaning small patches, wear gloves, goggles, and a respirator or mask that filters particles. Do not use bleach on porous surfaces like drywall, as it does not kill mold roots. Use a detergent solution and dry the area thoroughly. For large areas, call a professional who has the right equipment.

Preventing Future Growth

The right way to deal with cladosporium is to prevent it from starting. Keep your home dry by fixing leaks promptly and using dehumidifiers in damp rooms. Make sure bathrooms and kitchens have working exhaust fans, and open windows when weather allows. In Kirkland, you might run a dehumidifier during the wet season to keep indoor humidity in check.

Inspect your home regularly for water stains, musty odors, and condensation. Pay attention to areas where water can enter, such as roofs, windows, and pipes. If you find a leak, dry the area within 48 hours to stop mold growth. For hidden moisture, a water damage inspection can help you locate problems before they become major.

  • Use a dehumidifier in basements and crawl spaces
  • Insulate cold water pipes to reduce condensation
  • Keep closet doors slightly open for airflow
  • Wipe down shower walls after use
  • Check roof flashing and window seals each year
  • Remove and replace water-damaged drywall and carpet

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Frequently asked questions

Can cladosporium grow on wood?

Yes, cladosporium grows on wood, especially damp or water-damaged wood. It feeds on the cellulose in wood and can spread quickly if the wood stays wet. Drying the wood and fixing the moisture source is essential to stop it.

Is cladosporium dangerous to breathe?

For most people, breathing cladosporium spores is not dangerous, but it can cause allergy-like symptoms such as sneezing, coughing, or itchy eyes. People with asthma or weakened immune systems should avoid exposure and see a doctor if symptoms occur.

How do I remove cladosporium from walls?

For small patches, mix a little dish soap with water and scrub the area gently. Rinse and dry completely. Do not use bleach on drywall because it does not kill the roots. If the mold covers a large area or keeps coming back, have a professional remove it.

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