Order of installation is the same with a wood subfloor: sloped mud bed first (on the concrete), liner second, sloped mud bed on top of liner third, then tile. Travertine probably isn't the best material to use for a shower floor.

We are thinking of installing travertine tile for our newly remodeled dental office. We liked the pattern of a 3/8" thickness travertine from Peru - Angelica. Urgently need advise if 3/8" thickness is acceptable for a dental office? what would be the precaution of installation these pores (top and bottom) tile? Should I request installer to rough fill the bottom before the tile been laid? Thank you advance for any advise.

Usually the added weight of the SLC which has got to be thick to cover the in floor radient heat, is not recommended over 16" center joists and just ¾" plywood. It is not stout enough, and then your adding more weight with the thinset and tiles. Usually the area is 12" center joists or at least 1¼" of subfloor, or the joists are blocked from below. It doesn't sound as if your GC is educated in proper substrate requirements for natural stone, which are double that od clay ceramics. Sealing the surface only prior to setting is a very good idea, as a texture tile surface is impossible to clean, thinset or grout from. It should be sealed before setting, and then come time for grout, it is already sealed and ready to go for the grout to be easily cleaned and wiped down. It depends on the size of your grout joints as to whether to use sanded or unsanded. 1/8" and smaller is unsanded territory, and wider then that up to 1/2" is sanded grouts territory.

"Some people go to great lengths to have concrete floors. " And many of them regret it as they age and the stiffness of the floor takes its toll on knees, hips, and backs. Or you add cushioned mats to stand on creating one more thing to clean.