When warmer more humid air meets the cold wall condensation forms contributing to mold problems.
What causes mold on ceiling in bathroom.
I recommend replacing the fan with a constant flow unit such as the panasonic whispergreen fan.
Most homeowners claim that it is the primary reason of the black mold emergence.
That is the reason why condensation is very common in cold surfaces.
Any water that doesn t drain properly and sits in the drain creates a moisture problem.
Most people tend to close their bathroom doors when the shower is in use effectively trapping all the moisture laden steam produced by hot showers in the bathroom.
When moisture that is produced inside your bathroom comes in contact with the ceiling and becomes its resting place condensation begins.
Here is a link.
Any environment like this where water is collected and stands for long periods can easily grow mold.
Poor ventilation is one of the most common causes of mold and mildew in bathrooms.
If that s outside of your budget you can install a timer switch on the existing fan.
The main cause of mold on a bathroom ceiling is a broken or ineffective exhaust fan.
If your house has poor insulation this can encourage mold growth including on the ceiling.
Water coming out from basin bathtub and shower will create wet surfaces that are claimed by black mold as the place for it to live in.
In addition to water supply another cause of black mold infestation in the bathroom is related to the steam evaporation.
Aside from the water supply creating the fungus infestation in the ceiling the steam evaporation is another cause you can t look down.
This is the major cause of mold growth in bathroom ceilings.
Mold caused by blocked bathroom drains drains which do not drain water properly can also contribute to mold growing in bathtubs showers or basins.
When water moves through holes in a leaking roof mold can easily grow in the ceiling since it is regularly fed with what it needs to thrive.