Mold Behind Bathroom Wall
Most people never get to see behind
their bathroom walls, well this is what they would look like if you had
moisture soaking through the plaster board or drywall over a period of
time. Sometimes damage like this takes months, and sometimes years.
You can see the darker colors towards the bottom of the wall, this would be the mold and is usually toxic black mold. Don't let that scare you but some people are allergic to molds and mildew's, while others become sick for long periods of time, without knowing the cause.
Usually if the mold is contained behind the walls, it's not creating problems on the interior or living area of the home. However, it will be destroying the wood, drywall and anything else in its way, eventually needing to be repaired or replaced.
If you look at the picture where some of the button board paper has been scraped away (this area is the white spot on the middle left side of the picture), looked just to the right and you will see stains on the button board and you will notice stains above them.
These stains could be from a roof leak and not from your bathroom. Don't assume anything when doing forensic work on your home. Just because a water pipe is near the mold or other damaged parts of the home, doesn't mean that the water pipe is the problem.
This button board or plasterboard should be removed and replaced to prevent the mold from spreading. Replace any of the damaged wood if necessary. If your budget does not allow for this, make sure you spray bleach or chlorine on the mold and let this dry. This might not solve your problem entirely but could provide temporary relief.
The most important thing here isn't the mold but where the moisture is coming from, that is causing the mold to grow. Find out where the moisture is coming from and fix the problem, before it happens again.