QUESTIONWhat causes grout to crack on newly installed floors?
What cause water to wick up grout lines in a newly installed shower?
How much tilt should a shower curb have in order to ensure water drains off the curb and in to the shower?
ANSWERANSWER - If only the grout is cracking, and not the tile, then normally grout cracks due to excessive movement in the tile assembly for one reason or another.
There are many different types of tile assemblies, so you have to take into consideration the configuration and condition of the tile assembly. Although generally speaking, if water is wicking up the grout lines, either on the shower floor or up the wall from the shower floor, it could be due to the weep holes in the drain being plugged and not allowing the water to weep out.
The horizontal surface of the shower curb/dam should be slopped towards the shower floor drain. The slope should be a minimum of 1/4 inch per foot, but not more than 1/2 inch per foot.