Cladosporium species
The most common mold on earth, indoors and out
What it tells you about the building
Cladosporium dominates outdoor air in most climates, so its indoor presence is expected at background levels. The signal is pattern: concentrated growth on condensation surfaces — windows, registers, cold corners — points to humidity and thermal-bridge issues rather than bulk leaks.
Why it matters in assessments
As a predominantly outdoor genus, Cladosporium contributes to the outdoor-species side of indices like ERMI. Elevated indoor growth matters more as a humidity diagnostic than as a water-damage marker, though heavy indoor amplification is still a condition to correct.
What remediation requires
Surface cleaning plus environmental correction: improve ventilation, address thermal bridging and window condensation, and control humidity. Recurring growth after cleaning means the condensation driver was not fixed.
Olive-green to brown-black colonies with a suede-like texture, common on surfaces as spotty growth rather than large mats.
- Window sills and frames
- Bathroom surfaces and grout
- HVAC supply registers and coils
- Exterior-wall closets and cold corners
State editions
Where this species shows up depends on where local climate and housing stock meet its moisture requirement. Read the local picture:
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