Recently one of our tenants moved out and upon inspection of the master bath shower stall I was greeted by the sight of this:
Basically, the tile grout in the tiles near the floor eventually loses its sealing functionality and moisture seeps through the paces between the tiles causing the drywall backing to degrade. This weakens the tiles and causes even more moisture to get behind the tiles.
Here’s what it looks like behind the tiles. Yick!
What I do to repair this kind of problem is remove all the weak tiles until you find strong drywall/wallboard.
Remove any damaged drywall from the back of the tiles. I used a grout knife to scrape any paper and loose Thinset mortar from the back of the tiles, that way, I can use them again.
Cut to size and screw into place pieces of Durock� concrete wallboard to be used as the new backing for the tile. Durock� is great because it will not degrade if it becomes wet. These days, the entire backing of a shower stall or tub enclosure is usually Durock� or some kind of concrete wallboard.
Apply and texture a coat of Thinset� mortar to the Durock� wallboard and replace the old tiles.
Once the Thinset� is dry (usually overnight) use a good rubberized, sanded grout between the tiles.
And that’s it. Good for another 10 years and about $2000 saved from not re-doing the entire shower enclosure.
Oh, how I love property maintenance so.