Is moisture harmful to drywall?

Answer: Always
Explanation: That's why in moisture areas we use moisture resistant boards

Answer: Always
Explanation: Moisture causes dry wall to mold an swell

Answer: Always
Explanation: Moisture will cause mold. Drywall needs to be properly primed to avoid mold.

Answer: In most cases
Explanation: moisture resistant drywall is available, Will not stand up to flooding or long term exposer.

Answer: Always
Explanation: It can sweat and start crumbling within do time

Answer: In some cases
Explanation: Only in some cases, simply depending on the sheet. Some sheets such as DuRock are made to fight against moisture and are often installed in bathrooms/showers etc.

Answer: Always
Explanation: Drywall is not a water proof product. Even a moisture resistant gypsum product is not water proof.

Answer: In some cases
Explanation: Drywall that has been soaked by a leak or flooding is most definitely harmful to drywall because the perfect habitat for molds and fungi is created witch will quickly spread if you dont have it taken care of by a professional. Wetting just the surface of the drywall on the other hand is perfectly fine since it will dry before anything has a chance to grow.

Answer: In some cases
Explanation: Constant exposure to moisture can damage the drywall and many cases cause mold to form. In case where moisture is present, it is recommended to go with a moisture resistant drywall board.

Answer: Always
Explanation: in water areas

Answer: Always
Explanation: You have to use green board or blue board in areas where would be moister or water leak, usually water resistant boards get installed in bathrooms and kitchens. It's is important because moisture will eventually become mold and that could be dangerous for health and very costly to replace infected drywall, sometimes mold moves inside the wall as well and damages wood inside the wall which would have to be replaced as well!