On Mar 25, 8:10 am, wrote:
I have an old house. Person before me tiled over drywall (Not at
least greenboard!). I had a leak in the pipe to showhead that got the
drywall wet. Tile was put on with good layer of mastic so the mastic
itself is still okay. However after a week of running a dehumidifier
the paper has peeled away in spots and drywall is still crumbly. The
tile is still straight and not sagging and it's only a 2' x 3'
portion. I don't want to retile. So I am looking for a solution to
strenghten the drywall. I am thinking some good sealer paint might
act as a glue, but could act as a water trap to make matters worse?
Anyone have any ideas?

I'm not getting 100% of the picture but do You still have access to
the backside of the drywall?Is it damaged only behing the tile? If so
then maybe the crumbly stuff can be scraped away and something tougher
troweled on..Some fiber mesh added for strength if You think it's
needed.After scraping use some KILZ to prep it for the fillcoat..It
would'nt need to be pretty if it's hidden within the wall..