Unseen Damage
Often time there is damage behind a wall that can not be seen by the naked eye.
Moisture meters are often used to check material wetness and how far the water intrusion has gone. Many times this requires work on walls adjacent to the room in which the damage occurred.
Knowing where to look and what to look for is pivotal to preventing mold growth. It is important to know that many walls can be insulated or be wet behind the paint without showing any outward signs of being wet.
So next time you think you have a little leak, Call a professional to make sure its not beyond where you can see.