In my shower there is a recessed alcove along an exterior wall (concrete
block wall). The shower was put in about 4 years ago in place of a tub.

This recessed alcove recenly had a clack on one of the tiles, I don't know
if it is because of swelling from behind (*smells trouble*) or just caused
normal expansion/contraction. I decided to remove two of the tiles to
inspect. One horizontal and one vertical. As seen in the picture below:

http://img.villagephotos.com/p/2005-...6/DSC00001.JPG

The alcove has two sections, one on top and one at the bottom. You can tell
I removed a vertical tile at the bottom of the top alcove and a horizontal
tile (this is the one that was cracked) at the bottom alcove.

I did not see any moisture under there so I think that's OK.

However, I did a poor job of removing the vertical tile. In an effort to
not strain the adjacent tiles I pounded a chisel under that tile hoping to
pry it off. Only I also chiseled into the wall board under.

I looked closely at it and the contractor who did this attached a strip of
wonder board onto the wood stud behind. Then applied tile adhesive for the
tiles. It was probably one single strip of wonder from top to bottom of the
entire alcove. I saw one screw in the section I removed. Here is a close
up of what it look like right now:

http://img.villagephotos.com/p/2005-...6/DSC00002.JPG

I managed to remove a big chunk of the wallboard. I see a layer of mesh
below. What should I do to put back a surface for the tile to adhere to? I
see two options:

(1) Mix up some concrete patcher and float new concrete into the wall board
to build it back up. Only question here is I don't know how much of the
original wall board is left and whether doing this will be strong enough? I
have never floated concrete on a vertical surface either my guess is it's
not that easy.

(2) Use a grout saw to saw it off top and bottom of that section. Go buy a
new sheet of wonder board and break off a 6" x 10" piece and screw that onto
the wood stud again. If I did that the problem I see is I don't know how
many screws they used to originally attach the wall board to the stud. If
they used two and I exposed and remove one, then it means one section of it
will not be screwed on.

Are there other ways?

Thanks in advance for any advise.