This is for the top of the curb at the entrance to the shower? If you want a solid piece with no grout lines, then try a stone fabrication shop or stone yard. They'll almost always have odd-sized cutoffs from sectioning a slab. Pieces can normally had for a song, and they'll cut and polish as required for a few dollars more. Worth asking, and they'll have a variety of stone to choose from. Mongo

Perfect thermal isolation is an idealization; there is always some "thermal contact". The study of heat conduction between solids is thermal contact conductance (or thermal contact resistance). Thermal contact does not imply direct physical contact. -- http://en.wikipedia.org/wiki/Heat_conduction ++ http://en.wikipedia.org/wiki/Thermal_radiation = TWO factors that combine. Heat moves in a solid touching other solid matter. Slab to Tile. Tile to Slab. -- Not http://en.wikipedia.org/wiki/Convection -- The more general case : http://en.wikipedia.org/wiki/Thermal_contact http://en.wikipedia.org/wiki/Heat http://en.wikipedia.org/wiki/Heat_transfer http://en.wikipedia.org/wiki/Thermodynamics -- The whole subject can be studied from the opposite point of view. http://en.wikipedia.org/wiki/Thermal_insulation http://en.wikipedia.org/wiki/Radiant_barrier http://en.wikipedia.org/wiki/Multi-layer_insulation http://en.wikipedia.org/wiki/Building_insulation http://en.wikipedia.org/wiki/Building_insulation_materials Placing heat cables on a slab, under tile, means that you are heating the slab and the tile. More about this later.

I'd prefer that more grout had been left in the joints. They look dished out a bit too much, where too much grout was removed during the cleanup phase. I'd have preferred the grout to be more flush with the face of the tile. Looking closely at the first two photos, the darkened grout lines are all parallel to one another. In the first photo you can see the wet grout lines are all parallel to the edge of the drain. That leads me to believe that the "uphill" edges of the tiles are acting like mini dams and holding water, they are preventing water from easily flowing downhill to the drain. The second closeup photo, you see the same effect. All the damp grout lines are again parallel to one another. Again, to me that reflects a drainage issue. Not necessarily with the amount of floor pitch, but with the grout lines being so dished out that they hold water and slow drainage. Marble is porous and can absorb water. With the grout lines being a bit too raked out, the edges of the marble hexes are exposed. Water held against the tile edge can lead to absorption into the marble. The crack in the grout in that second photo, you also wrote that there are other cracks. That's usually a sign of too much water used in the grout mix, or that sanded grout should have been used instead of unsanded. Unsanded should be used in joints less than 1/8" wide. Cracks can also indicate movement in the floor, but that shouldn't be an issue with a properly set Kerdi Tray. As far as him having used a preformed Kerdi-Tray, if he did, it appears that is was certainly cut down in an awkward manner. The drain is no where near centered in the shower. So if he did some filling here and there with mud or thinset to even out the floor pitch or edge elevations, that could have be part of the problem. But that's supposition on my part. About the only other thing I could question is that often times with small tiles, when the sheets are set into the thinset, thinset can ooze up between the hex tiles and partially fill the grout lines. That thinset needs to be cleaned out so the grout lines can be completely filled with grout. If it's not, you can get uneven thicknesses of grout, think of it as a veneer of grout over a blob of thinset. That can result in uneven water absorption, the grout cracking, etc. All that aside...with this being your second go-around, he should have install the sloped Kerdi Tray and thinsetted it to the subfloor. Then he should have set the Kerdi drain. Then he should have thinsetted Kerdi Membrane (an orange colored sheet material) over the Kerdi Tray, then tiled on the Kerdi Membrane. I'd be interested in how he tied the Kerdi Membrane in with the wall membrane IF he used Kerdi Membrane over the Kerdi Tray. Best. Mongo

First off, it doesn't matter if some sealer gets in the joints or not. Even with the sealer-- you let the grout stay on the tile long enough to dry nice and hard, it's not coming off without a fight. Same in the grout joint. Now, as for whether they should or shouldn't seal, leave it up to your installer. Just make him aware that however he decides to do it, you expect the stone to be impeccably clean when he's done. The reason I say this is because some installers, including myself, prefer to grout the stone raw, while others rather seal it first. There are very few surfaces I'll seal first, and I have a real problem with customers telling me I HAVE to seal a surface before I grout. I just went through this with a general contractor I do alot of business with. We tiled his own house under construction, and his master shower was chiarro tumbled marble (looks like swiss cheese), and I refused to seal it first. In fact it won't be sealed until this friday. He wasn't disappointed. Like I said, let them know your expectations, and that they'll only be paid once those expectations are met, and let them take it from there.