I recently purchased a home previously occupied by someone who fancied themselves quite the "do-it-yourselfer" He installed shower tile directly on the wall above the shower surround, and on the shower surround itself. No greenboard. It is grouted haphazardly, etc. I see no other option than to remove it - Help! How do I get the tile off - will I have to install new wallboard?
Had a similar situation in a house recently. The nails in the wallboard/surround were not meant for a "wet area." Consequently, they rusted, expanded and pushed out the tile. You might save yourself future headaches -- think what might be hidden behind there -- by tearing it out and replacing it all. You'd probably also save time by not having to cope with the vagaries of the previous installation.