Memnoniella is a mold genus closely related to Stachybotrys chartarum and is commonly found in environments with severe or long-standing moisture.

Indoors, it typically appears only when building materials remain wet for extended periods, rather than from brief humidity or short leaks.

Its presence often reflects water damage that was hidden, slow to dry, or never fully addressed.

What Memnoniella looks like

Memnoniella usually appears dark brown to black.

Growth often looks powdery or sooty rather than slimy, especially when compared to its close relative Stachybotrys.

Because of its color and location, it is sometimes misidentified as generic “black mold” or confused with Torula on water-damaged materials.

What Memnoniella needs to grow

Memnoniella requires persistent moisture and cellulose-rich materials.

Common growth conditions include:

• Long-term roof or plumbing leaks
• Flooded materials that dried slowly or unevenly
• Chronically wet drywall or insulation
• Areas sealed back up before fully drying

It commonly grows on drywall paper backing, wood framing, ceiling materials, and fiberboard.

Common exposure effects

Reported responses to Memnoniella exposure vary and are often associated with prolonged or repeated exposure.

Effects may become more noticeable when contaminated materials are disturbed during repairs or demolition.

Commonly reported effects include:

• Nasal or sinus irritation
• Headaches or head pressure
• Eye or throat irritation
• Fatigue or a general sense of unwellness in damp spaces

These effects overlap with those reported for other severe water-damage molds such as Chaetomium and Fusarium.

Why Memnoniella often indicates advanced moisture damage

Memnoniella does not typically appear unless materials remain wet for an extended time.

Its presence often means drying was delayed, incomplete, or obstructed by finishes or insulation.

This distinguishes it from molds like Cladosporium, which can grow from condensation alone.

Cleaning versus removal considerations

Surface cleaning is rarely sufficient when Memnoniella is present.

Because it typically colonizes porous, water-damaged materials, removal is usually required.

Disturbing contaminated materials without containment can significantly increase airborne spread.

Safe containment and remediation principles

Effective remediation focuses on moisture correction and proper material handling.

Best-practice principles include:

• Identifying and stopping all moisture sources
• Removing contaminated porous materials
• Using containment and negative air during demolition
• HEPA filtration during cleanup
• Confirming complete drying before rebuilding

Covering or sealing over affected materials without removal often leads to recurrence.

When professional remediation is usually recommended

Professional remediation is often appropriate when:

• Mold is present in walls, ceilings, or structural materials
• Growth followed flooding or long-term leaks
• Multiple materials are affected
• Occupants exp