It may be from a plumbing leak a roof leak or a severe lack of ventilation.
Mushrooms growing on roof.
Mushrooms in the house mushrooms growing indoors present a classic sign of a moisture problem.
Fungi growth can many times be found far away from the source of moisture.
I haven t panicked because the moisture meter shows nothing on the opposite drywall side but it s obvious the siding is getting damp to the point of growing mushrooms.
Correcting the moisture problem is the first step in the eradication procedure.
If the stump is still there you can have it removed.
Fungus so bad there are now mushrooms growing out of the floors of the gym.
It s a combination of algae and fungus and usually has a light mint green color.
From your description you may have lichen growing on the surface of your roof.
Leaks have ruined equipment created mold issues and fungus.
The mushrooms are growing on my rental house not many only a small side of the house but persistent over the 3 years in small quantity since i ve owned this rental.
It s not unusual to see mushrooms growing in the basement that derive their moisture from a rooftop leak.
If you have an area where a tree used to stand even if the stump is gone the dead roots underground may encourage mushroom growth.
In this situation first the leak must be fixed and secondly the roof must be treated also in order to successfully kill the root of the infestation.