Just moved into this house a few months ago, and noticed the stub wall in the shower that holds the controls has cracked grout.
I'm guessing that somehow water got in behind the tiles and started to swell the supporting studs, which blew out all of the grout in the area.
What should I do to fix this?
You can see the tile is separating perpendicular to its surface.
Here too.
It looks like the problem is not just the grout (which fills the gap between tiles) but also may be the tile adhesive is separating from the supporting structure (possibly plasterboard/drywall).
You can remove grout from between tiles using a variety of tools designed for this purpose. Then you can re-apply grout (and sealant if needed)
It seems likely that water has penetrated that structure, it might be best to open it up and assess what damage has been done and how the water got in.
In your case you may need to remove all the tiles, repair the supporting structure and re-tile. It's the only way to get the tiles to align neatly at the corners.
