Installing wonder board over existing drywall?
Answers: You'd be defeating the entire purpose of using the wonder board by putting it over drywall. It's not that tough to remove drywall and you'll be able to see if within is any water-damage behind the drywall that you involve to repair once the drywall is down. Wonder board isn't water-proof, it just doesn't plunge apart or grow mold if it gets damp like your usual drywall does. If the wonder board gets drizzly enough, the drywall bringing up the rear it isn't going to be dry for very long, and since it will be covered, it will help yourself to a VERY long time to dry, meaning you hold a much better chance for mold to start growing. They put up for sale a product at Home Depot that you can spray on the inside of the walls before installing drywall or wonder board that will prevent the growth of mold and mildew, you might want to look into that as very well.
No problem just use longer screw or nails.
More Questions and Answers...