Tile Marble Granite deals with improper jobs on a daily basis.
We got hired to partial fix this windowsill. It turned out the water damage was far greater than we initially thought. The entire external wall was soaking wet. The water was dripping on the windowsill causing the water damage. The tiles were held in place by ''Elastoplast Bandages''. As we started to remove the bottom portion of the shower, the entire wall started to come off. Even the bricks were messed up. We had to hire a dehumidifier to dry up the place, it took about six weeks to dry. The plaster was replaced with render (portland cement & sharp sand mixture). The wall had to be waterproofed prior to tiling using the proper materials and a waterproof membrane. The tiled windowsill was replaced with a marble slab. See pictures below.
Shower windowsill- work in progress