Regardless of what type of tile you install over your garage, none of the installations will be waterproof unless you waterproof under the tile first.

It is possible to embed 12×12 inch ceramic tiles into a freshly poured concrete slab, but there are a lot factors to consider. It is recommended to let the concrete cure for 28 days before adhering the tile to it.

First of all if it was installed correctly you wouldn’t have a problem. To fully figure it out I would have to perform a forensic intrusive inspection, which probably isn’t practical for a small shower.

No you cannot use a stucco mix as a mortar bed for adjusting the uneven concrete floor.

For an ADA shower you can’t have a curb/dam. You need a minimum slope to drain of ¼” per foot and no more than ½” per foot. You need a two part drain with weeps for the primary waterproof membrane to clamp to.

Xypex is suppose to waterproof the concrete. So in theory it should prevent moisture migration in the concrete wall to help reduce the possibility of efflorescence.

The proper way to cut glass tile is either with a continuous rim diamond blade either wet or dry. Also you can cut glass tile with manual tile cutters.

You should use an ASTM C920 silicone sealant suitable for granite.

The term mastic in the ceramic tile industry is an organic adhesive per ANSI A136.1. Type 1 and type 2 organic adhesives are to be used only in interior wall and ceilings with limited water exposure. Type 1 is more resistant to water than type 2 adhesives.

Exterior decks are one of the most common failures in building construction because they are normally constructed incorrectly.