here's what your shower should look like w/cement board (CBU, HardieBoard, DuraRock)
this is what's painted over it to waterproof it
should look like this. Now you can tile
Kerdi shower system (just another way of waterproofing. Kerdi is a complete system.)
If doing a cement board wall, the shower pan should have this. PVC liner (supported by surrounding wood studs.
no nails in the liner or on the curb!!
then a sloped mortar bed atop
and over the curb to finish looking like this
Now you can tile.
Show him these pictures.
did he do anything resembling any of this? NO? then it's a tear out
Q