Hi Pearl. I used a TEC premixed grout. I explained to the guys at the John Bridge Tile forum that I was tiling over 400 sq. ft. in my spare time, and it would take me weeks (actually months, but I took the summer off). I said that at times I might only get 25 sq ft done and would not be able to grout it all at once - and that there was the possibility of being interrupted to deal with the family:) One guy suggested a premixed grout, and specified a type which I could not find in my area. I know TEC is a pretty good brand so I used their's instead. I also was very tired of mixing up powders - I would mix the thinset in my garage and lug it down to the basement so the thought of a premixed grout was lovely - no mixing, snap the lid back on when interrupted and consistent color. I think it is twice the cost of powdered, but the perks outweighed the cost given the chore. I used the Pearl color. It takes 24 hours before you can use the floor. On a smaller job I would not mind the powdered, though the color can vary if you add more or less water - so be consistent with every batch you mix. This is what I used: https://www.menards.com/main/flooring-rugs/tile-stone/tile-installation-maintenance/tile-grout-caulk/tec-reg-ready-to-use-premixed-grout-647-1-2-gal/p-1444432148471.htm

"@MongoCT - thank you - I visualize your explanation - can you elaborate as to how they would have avoided that situation ? should the drywall not drop all the way down? or the waterproofing should have taken care of it?" Jim, here are the installation instructions from the manufacturer. If the link does not work, which can happen with links to pdf documents, just google "denshield installation instructions". See the drawing and text on page 6. The general idea is that: 1) A preslope of mud should have been placed on the shower subfloor, properly detailed. 2) On top of that sloped mud goes your waterproof membrane. The edges of the membrane get turned up the walls. With the membrane going on top of a sloped surface, the membrane is now sloped to the drain, which is a requirement in the building code. It is a code violation for the membrane to be placed directly on a flat surface/subfloor. The membrane itself needs to be sloped. 3) On top of that membrane goes another layer of deck mud. 4) The bottom edge of the Denshield gets held just above the deck mud. The Denshield should not contact the mud. 5) The gap between the denshield and the mud gets completely filled with sealant. The objective is to get sealant on the entire 1/2" thick edge of the denshield panel so the exposed gypsum core will be sealed, so it will never see moisture from the mud. On the curb? If yours was a wood core curb, built up from stacked 2x4s? There are various ways to do this, however... The membrane gets wrapped over the wood curb, with the membrane fastened to the curb only on the outside face of the curb. No fasteners go through the membrane on the inside face or top of the curb. Most folk will then wrap the membraned curb with an upside-down "U" formed out of expanded diamond lathed. No fasteners. It's a somewhat loose friction fit. You want the lathe to follow the shape of the curb, but you don't want the metal edges to contact the membrane. The lathe is coated with a thickness of Mortar/mud. Mortar gets placed on the inside, top, and outside face of the curb, completely encasing the expanded lathe and the curb within. It gets shaped as needed, with the top pitched slightly into the shower. The lathe provides structure for the mud to prevent it from slumping. When the mud cures, you tile on the mud. That gives you a sturdy curb base to tile on with no holes in the membrane on the top and inside "wet" faces of the curb. The Denshield instructions I linked to earlier show a rough sectional of a wood core shower curb covered with the membrane and mortar. They do not show the upside-down "U" of lathe that I wrote about. If installed, it would be centered in the thickness of mortar that covers the curb. With all that written? I agree with the others, that surface applied membranes are indeed superior. In the age of computers? Installation instructions are available from the manufacturers' websites. While you have to sort through them and discard the whackos, there are also good youtube videos available. Any shower system is only as effective as the person installing it. While I'm not a fan of Denshield myself, if it had been installed properly you should have had a properly performing shower. The gypsum core is the weak point with Denshield. Any exposed panel edge, or any drilled hole? The exposed gypsum needs to be protected from exposure to water. Referencing your last sentence: "...or the waterproofing should have taken care of it?" In a Denshield shower, the wall waterproofing is the acrylic surface of the Denshield panels. Any panel edges or drilled holes, the exposed gypsum core needs to be sealed with sealant. The shower floor, the waterproofing is the membrane. At the base of the walls where the two meet, the Denshield goes OVER the membrane. With the Denshield alone, your installer failed to protect the panel edges. He buried the bottom of the Denshield panels in mud that, for the most part after the first week of showering, the mud will become saturated with moisture. And he also used Denshield on the curb which is a no-no. I wrote a lot, I do hope it makes sense.

Actual stone or stone tile? Stone of the type used for flooring would not be suitable for a shower. It would not drain completely and you would have standing water in the shower nearly all the time.. Stone tile would be flat and smooth enough to drain, but would have to be sealed and resealed frequently. Quite a maintenance chore.

The 'grout at change of plane' is a red flag. That tells us there are more issues BEHIND the stone...or at least there WILL be. Grout is not flexible enough to change planes. It can be vertical OR horizontal but not BOTH at the same time (like the floor/wall intersection). Caulking is required at all change of planes...that includes the corners of all the walls, the floor/wall interface as well as any shower nooks. Sigh. Is this person a TILE SETTER or a GC??? A professional tile setter KNOWS all of this, GCs are not always up on the 'specialties' like tiling or flooring. Now we question EVERYTHING: 1. What did you see on the WALLS before the tile was installed? What was the colour of the surface JUST BEFORE s/he applied the tiles? 2. Was the shower pan FLOOD TESTED for 24 hours (the drain plugged and the pan flooded with the water standing for 24 hours)? Was this done BEFORE the tiles were installed? 3. What do the edges of the wall tiles look like (where tile meets bathroom drywall)? 4. Caulking around taps/plumbing? Anything this person touched now has to be assessed for correctness. This is where in-progress photos help A LOT. Do you have any photos of the 'before' demolition...how about just before he started work? Anything?