Common Types of Household Mold

There are thousands of mold species, but a handful show up in homes again and again. Here's what to know — and why color alone never tells the whole story.

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Five molds you'll actually run into

Cladosporium

One of the most common indoor and outdoor molds. Olive-green to brown or black, often on fabrics, carpets and damp surfaces.

Aspergillus

A very common indoor mold in many colors. Some species can affect people with weakened immune systems or lung conditions.

Penicillium

Blue-green and fast-spreading, often found on water-damaged materials, wallpaper and fabrics. Spreads easily through the air.

Alternaria

Dark green or brown and velvety, common in damp spots like showers, under sinks and around windows.

Stachybotrys

The so-called “toxic black mold.” Dark and slimy, it grows on constantly wet, cellulose-rich materials and needs lab testing to confirm.

Color is a clue, not a diagnosis

It's tempting to diagnose mold by color, but it doesn't work — the same species can appear in different colors, and different species can look identical. Only lab testing confirms what you're dealing with. The one thing every type has in common: they all need moisture, so the fix always starts with the water.

Types FAQs

Which mold is most dangerous?

Risk depends more on the amount and the exposure than the species. Stachybotrys gets the most attention, but any heavy indoor mold growth is worth addressing.

Can I identify mold by its color?

No. Color is only a hint — the same species varies in color and different species look alike. Lab testing is the only way to confirm.

Do all molds need moisture?

Yes. Every household mold needs moisture to grow, which is why fixing the water source is the key to keeping it gone.

Should I test to identify the type?

Testing helps when the source is hidden, for health concerns, or to document a claim. For obvious growth from a known leak, removal usually matters more than naming the species.

Want to know what's growing?

We collect and submit lab samples as part of an inspection. Call (970) 373-1522.

Call (970) 373-1522