@millworkman the shower was finished in March ‘22. It was custom built and yes, we have contacted the tiler. Although it is no longer under warranty, I hope applying silicone caulk will remedy the situation. I am aware of potential plane shifting. What would cause movement in the floor?

Use a waterproof silicone sealant immediately. Should have been done during installation

He probably used a cheap sealer on the pebble floor

The floor cracking could be a couple things:

1. foam pan(?) could be flexing under point load if some of the pebbles are more round on the back

2. poor mortar coverage, especially on the stones themselves (ie, the mortar is contacting the backing mesh rather than the stones), which allows the pebbles to move

Do you have photos from during construction?

This is all I have.

This is all I have on file.

What did they use to waterproof behind the tile?

Schluter system

Ok that looks a lot like one of Schluter's foam pans. I think both aforementioned possibilities are still likely. You'll be best off bringing in your tile person to diagnose on site.

Edit: one more question - Do you know which grout was used? I see the Latisil for silicone, so I'm assuming Laticrete something. Some grouts aren't rated for pebble floors....

Thanks for your feedback. I’ll ask as I’m unsure which grout was used. The tiler was asked to return, and did, but I’m still awaiting a response. I’ll message them. TY!