Cladosporium
RoutineCladosporium species
Cladosporium is the most common mould on earth and the most common one indoors. It grows happily at ordinary room temperature on ordinary humidity, which is why it appears on window frames, bathroom walls, fabrics and painted surfaces without any leak involved. It is a well-known allergen and a routine cleaning job rather than an emergency.
Quick facts
- Appearance
- Olive-green, brown or near black with a suede-like velvety texture, growing in discrete rounded patches that merge. Dry to the touch and powdery when disturbed.
- Moisture
- Grows on humidity alone — no leak needed
- Smell
- Mild musty.
- Colours
- green, black, brown, grey
- Texture
- velvety, powdery
- Surfaces
- drywall, fabric, wood, grout
How to recognise it
- Velvety, suede-like texture that is dry rather than slimy.
- Olive-green to black, in rounded patches.
- Grows on humidity alone — no leak required.
- Very often the black growth on window sills and bathroom walls that people fear is Stachybotrys.
What it tells you about the building
Relative humidity persistently above roughly 60%, or surfaces cold enough to condense. Ventilation and a dehumidifier address it.
What it gets confused with
One observation settles each of these.
Stachybotrys is slimy and needs soaked material. Cladosporium is dry, velvety and grows on humidity.
Aspergillus is more powdery with a granular surface; separating them reliably needs a microscope, and the response is the same.
Where it turns up
The species matters less than you think
- Public health guidance is to remove all indoor mould regardless of type. The CDC and EPA do not recommend routine species testing for ordinary households, because the response does not change: find the water, stop it, remove the growth.
- “Toxic black mould” is a marketing phrase, not a category. Stachybotrys is real and does need soaked material to grow, so finding it tells you something useful about your building. But the health effects that are well established — allergy, asthma aggravation, irritation — are not specific to it.
- Mould without water does not persist. Cleaning growth while leaving the moisture source is why it comes back. The leak, the condensation or the ventilation is the actual problem.
Call a professional for areas larger than about 10 square feet, for anything in HVAC ductwork, after sewage or flood water, or if anyone in the household is immunocompromised or has a lung condition.